Combustion Chamber Size Vs. Burnrate? Also Squish VS. Swirl

[Captain Bondo]

Anyone have any good info or thoughts on these 2 compromises? Or what appear to be compromises?

It's odd, some of the best flow improvements on the 8v head lie in combustion chamber valve unshrouding. But I've been thinking, does moving the chamber walls further away slow down the burn considerably? Basically, creating a longer distance for the flame front to travel?

Also, my chambers have been modified such that if you draw and imaginary line extending from the edge of the valve seat out to the chamber wall, the "cut" from the unshrouded material is in-;ine with this imaginary line (which is standard porting practice) and then the cut extends until it is essentially tangential with the bore.

This allows the gases to follow the most natural path into/out of the port.
This tends to leave a little material near the roof of the chamber which apparently helps swirl.

Swirl is also a major factor in burn rate, since even mixture and fuel being dispersed in an aerosol-like format evenly througout the chamber will create the most even burn.
How does an unshroud like I described above effect swirl?
Another thing that improves swirl is a large piston-to-deck value, but that destroys squish, which is obviously important. So how can we maximize swirl and burnrate yet still improve gas flow?

Anyone have nay thoughts on this? My assumption is that you just try to run a flat top, do your unshrouding as efficiently as possible and leave it at that. Just thought I'd see what others more knowledgable think. :)

[Anonymous]

Cappy, this will be a lengthy extended discussion: this is just part 1...... :D :D

CC size affects burn time duration...the larger the CC, the farther the flame front has to go to burn all the fuel: more time til done...you are right there; or I should say we are agreed.

you say unshrouding the valves improves flow.....okay....but at what cost, if any? also: is that the "best" way to do that? [(I am really getting to hate that word: "BEST".....it has the wrong connotation)]...

what I mean by that is this: if unshrouding the valves improves flow but creates or exacerbates other problems, is that the route to follow?

you state an obvious side effect: larger CC/longer burn time....another side effect is reduced squish zone--you've belled out the head part of the CC--so there is less head surface to come into close proximity to the piston crown to make good squish.....(presupposing that you set up the deck height to give a good squish height)

a side effect to that result is diminished squish-induced swirl that occurs just prior to spark ignition of the A/F mix....

another side effect of the belled-out head CC is a larger floor for the burn chamber: the less squish zone between the head and crown means that the size of the floor area for the burn is larger...also lengthening the burn time....and transmittimg more heat to more of the piston crown...and that makes its own problems, which we can discuss in another installment....

so what have you accomplished so far?--rhetorical/not accusatory--.....

well, you have "improved" flow past the valves.....

at what cost?....larger CC; reduced squish zone; larger CC floor...(to name a few)...

resulting in: longer burn time; a larger burn chamber; less squish-induced swirl; more area of the piston crown exposed to more heat....(also to name a few, but not necessarily all)...

that does not seem to me to be a win-win....

to get to the answer you are asking for, we will need to analyze what you are trying to accomplish and how to get there with fewer bad side effects.....

what is it that you are trying to accomplish/achieve/obtain/reach/and make happen?
and if you tell me that you just "want to improve flow", then I will get upset at your over-simplified answer....flow is only a part of the picture.....and only a part of the answer....

to assist your ruminations: why is it that closed chamber heads make more power than open chamber heads? YES. they do.....

answer that, and you will have a part of the answer to your question...

[Captain Bondo]

Well, the idea with unshrouding that i described, the floor itself is not enlarged, material at the floor is left there, partially because of swirl, and partially because it does not help flow to remove it.

Also, the actual quench pads are relatively untouched, especially opposite the sparkplug at the point where the flame front travels furthest.

Another though is that the increased burn time can be compensated for with more total timing, so if the chamber is increased for flow, but the mixture can be kept even, then even though the burn time is longer, it is as CONSISTENT as possible (which i think is a big key) and still fairly complete, so good pressure is developed.

My goal is not to improve flow per se, my goal is to develop the highest BMEP possible at a given octane level. I know better than to think port flow is the end-all be all.

The reason unshrouding works, as far as I can tell, is that the positive effects on combustion chamber pressure seen by the improvement in ve and cylinder filling more than offsets the negative effects on it due to the increase in burn time.

But the goal here is a combustion pressure/octane rating ratio that is as high as possible. A good goal I think? possibly THE goal?

[Anonymous]

reprise:

before proceeding further in this discussion, some clarifications need to be made...

my comments on the head work you have done were in part based on viewing the pics you posted on pbase......

I am not desirous of turning this into a critique of the reshaping and reworking of metal that you did on the 398 head....I would submit that to the discerning eye of one like Mike Aaro. I am confident that he could look at the head and rattle off at least a dozen things that you did well and otherwise. And I would listen very closely to his comments.

That said, I would submit that there are issues involved with improving flow through the ports of a cylinder head that are much different than just making the "pipe" a larger diameter...among them:

....the flow is not in a straight line; and because of that, the sizes and shapes of the radius' along those turns are critical...and often, just making the "hole" larger actually impedes flow....

....the shape of the bowl--on the intake side-- affects the flow volume/velocity and the swirl of the incoming air fuel mix.....AND affects the direction of the flow into the cylinder....if altered incorrectly, the flow will be directed at the cylinder wall--a barrier-- instead of being directed towards the middle of the bore to create a vortex swirl....

....to that end, I submit that flow testing a head that is not mounted on a fixture that recreates the conditions of the engine--the confines of the cylinder, for example--is self-delusional....I also expect severe disagreement with that assertion....

I will return to cylinder head improvements later in this discussion; there are some options that will deserve scrutiny, comment, and knock-down, drag-out fighting over...

preface to part 2:

a good discussion of the topics you have raised and the questions you have asked necessitate some further clarification on your part....

such as.....what other mods/changes have you done to your engine etc....and some indication of planned further enhancement....

.... a statement of usage or goal for usage of the engine, ie how do you drive it or intend to drive and use it.....

....and a statement of method.....NA? turbo'd? stock boost? high boost/high EBR? high boost/low EBR?

I request these so that we are all talking apples and apples....

the topics raised and the questions asked are, to myself at least, very important.....and there are aspects of engine performance involved therein that we have not yet broached.....hopefully, we will....

I look forward to your reply...

[700mopareater]

Hey, this is a good read :rockon:

Keep this one going, i'm learning a lot on it

[G96nt]

guys...
after Reading Through.. and gettign What I could From it...


why Are We going through hell to get more air Through a 8-valve head?

I'm assuming the CFM potential of the 8-valve is less than The DOHC (unless the valves Are half the size of the 8-valve? or if The lift/duration is that little of the DOHC)

why Are you scratching, and pulling to get from the SOHC, when the DOHC is a bit easier?

I'm sorry if the principal Is too simple? maybe I'm missing a lot?

but, if you can keep a similar combustion Chamber shape, and volume, but allow for much free-er Flowing setup.. it just makes for higher efficiency. Plus, you now have an extra pair of Valves/cylinder to remove heat from the motor which is a big plus for the Turbos


I think what I'm getting at...

why not go DOHC?
I'm Assuming you can Use the timing belt from a DOHC, as Well as cam-gears to make the timing work (similar to putting DOHC on a SOHC mitsubishi 4g64)

this would yeild a MUCH more Efficient intake/exhaust path..(and possibly raise compression From 7.5:1 to something more performance-oriented like 8.5:1, or 9:1?

[Captain Bondo]

my comments on the head work you have done were in part based on viewing the pics you posted on pbase......

"I am not desirous of turning this into a critique of the reshaping and reworking of metal that you did on the 398 head....I would submit that to the discerning eye of one like Mike Aaro."

Would be cool for him to comment, although i think that might be getting pretty close to talking about trade secrets, and certainly would not expect him to comment in-depth. ;) Which i fully am ok with and understand.

"I am confident that he could look at the head and rattle off at least a dozen things that you did well and otherwise. And I would listen very closely to his comments."

Agreed. there are some things (primarily the chamber floor) that could be done better.

"....the flow is not in a straight line; and because of that, the sizes and shapes of the radius' along those turns are critical...and often, just making the "hole" larger actually impedes flow...."

Agreed. Especially short side radius are key at both ports, and the exhaust short side is terrible, it's almost sharp, like you could cut yourself on it almost. My head porter made several disdainful comments about this. :)

Interesting side note for those listening in (stealth knows): the bigger your valves get 9especially exhaust in this case) the tighter the short side gets... another interesting tradeoff...

"....the shape of the bowl--on the intake side-- affects the flow volume/velocity and the swirl of the incoming air fuel mix.....AND affects the direction of the flow into the cylinder....if altered incorrectly, the flow will be directed at the cylinder wall"

Agreed again, another point that my head porter discussed, this relates to what i mentioned about the chamber unshroud beginning in-line with the seat, and ending-in line with the bore.


"....to that end, I submit that flow testing a head that is not mounted on a fixture that recreates the conditions of the engine--the confines of the cylinder, for example--is self-delusional....I also expect severe disagreement with that assertion...."

None here. Especially on the intake side, the bore is an "extension" of the combustion chamber, which is in turn a extension of the bowl/seat.
The entire flow path needs to be accounted for IMO.


"a good discussion of the topics you have raised and the questions you have asked necessitate some further clarification on your part....

such as.....what other mods/changes have you done to your engine etc....and some indication of planned further enhancement...."

well, not a lot. major modification are the head, which is fitted with a K cam at this point, as well as the huge IC. I also have a header in the works- basically just large, short primaries.

".... a statement of usage or goal for usage of the engine, ie how do you drive it or intend to drive and use it....."

I plan to drive it like an animal. LOL. but really, it's going to be a street car, but I can put up with a lot "driveability" wise. Expect redline to be about 7000rpm, with main useable power around 4000-6500

"....and a statement of method.....NA? turbo'd? stock boost? high boost/high EBR? high boost/low EBR?"

Turbo. With the header will be fitted a Super 70 trim hybrid, 63 A/R exhaust side. Boost anywhere from 18-25psi on toluene. ;)

basic premise of my project is: better than stock breathing, expecially on the exhaust side so maximize the benfits of a higher lift cam, low backpressure, lots of efficient boost with a lowish CR (8.2:1), excellent intercooling, and correct engine control.


"the topics raised and the questions asked are, to myself at least, very important.....and there are aspects of engine performance involved therein that we have not yet broached.....hopefully, we will.... "

That's the hope. ;)

looking forward to your continued observations...

[SLO240]

On the topic or swirl. If swirl creates a more even and "better" A/F mixture, would it be benificial to add a vortex patern to the to the walls of the head, to "spin" the incoming air and fuel and direct it into the chamber, much like the rifling on a gun to spin the bullet for better accuracy. Or would that kind of modification create more hinderance and no benefits.

[Anonymous]

G96nt...contrary to popular misconception, I would suggest that a well-prepped 8v head can perform as well as a similarly prepped 16v head....ask Mike Aaro...

if I were doing a Street/Strip or Racer approach, I might consider the hassle of going 16v....but since I am normally a Daily Driver--and occasionally a 004 Bondo syndrome "animal" enjoying the turbine whine and exhaust roar-- I see no need to go through the effort of converting to 16v.....I can get what I want with the 8v.....and I will admit a personal antipathy towards the 16v.....and yes, it is a personal choice....if 16v turns you on, go for it....

further, I would not describe it as going through hell re the 8v.....this will be explained as the discussion continues.....no offence intended...

SLO240...

what you describe has been tried, with less than gratifying results....cuz when the air/fuel mix reaches the bowl, then turns and spreads around the intake valve, any swirl created in the runner is undone and totally redone....the bowl/valve seat area is one of the critical spots....

but you're thinking in the right direction.....swirl is very important....

Cappy, thanks for the info....will work on part 2....I have a few questions for you....

[Boris740]

I wish I had a camera. I just finished porting and polishing a 530 head. I was afraid to remove to much material as not to bugger the CR. Instead of unshrouding the intakes I have undercut a grove in the wall nearest to the intake valve and in the direction of the sparkplug. The profile of that part of the wall now resembles a semicircle. This was to improve the swirl by providing a easier path for the intake gasses in that direction. In order to compensate somewhat for the removed material I had those rectangular indents opposite to the sparkplugs fill welded. The exhaust valves were mildly unshrouded. The valves were polished to a chrome shine. The head is out for three angle valve grind and when it comes back I am putting in the Enem V15 cam.

[Bready]

Great thread

Nice to hear from the mighty stealth again.

...pardon the interruption.

JB
KTP

[Anonymous]

I was pointed to an excellent source of info on head flow work parameters and guidelines; which reminded me of some things that need to part of this discussion....and I also reviewed some material I had read a while back....

before proceeding further, some items related to porting heads for max flow need mention....

the one thing that limits the maximum flow obtainable is the size of the valve head......and the shape of the valve head can have an effect as well...

most sources I have consulted strongly caution against the tendency to enlarge the size of the ports, stating that velocity through the passage is the more important thing, and that making the cross-sectional area of the passage too large in relation the the valve area would actually reduce maximum power...

in other words, for a particular valve size, there is an optimal cross-sectional area for the runner (the port) in order to achieve the maximum flow....if you exceed that max size, you WILL reduce the maximum power output....why? because maximum power is obtained when you have the smallest port cross-section that will deliver the flow.....

let me rephrase that once more: the limiting factor for maximum flow through the port is the size of the valve head: it's area....if you make the port too large in diameter (it's cross-sectional area) for that valve head area, you WILL reduce the maximum power that that head can make....because you have affected negatively the velocity through the port....and the velocity of the flow has a serious impact on power making capability....yup, those ports are HUGE...they be BEEEYOUTEEFULL....and the motor makes less power......

OH NO!!! CAN'T BE!!! I would suggest visiting the superflow.com website....(they make flowbenches)....go to the support section and read the FAQs.....

and for further information on valve area and port size relationships and problems, I suggest going to www.g-speed.com/pbh and reading the article on cylinder head tech, written by a guy whose company does 700hp turbo porsches....INTERESTING STUFF!!!

after reading the info from those sources, I am definitely NOT going to get out my dremels and go after my 398 SCP......but the choice is yours....

besides cautioning against going nuts with the dremel, the one thing that really stood out was the statement that the VALVE is the limiter of max flow.....HMMMMMM....sounds like if I really want to increase the flow through my head, I had better evaluate the valve sizes and probably go with larger valves...or at least a larger exhaust valve.....

HMMMMMM....that coincides exactly with what I have read at and heard from UNITEK......

Cappy, I was pleasantly surprised when you said that you had gone over your head with a "head guy"....I apologize, because I had thought that you had just done the dremel thing.....my error....and I am glad I was mistaken; the head really looks sweet....

a sidenote: in the g-speed article, the author discusses multi-valve heads....his conclusions are worth the read.....

now that those loose ends are tidied up, I want to broach squish and swirl again.....

"the goal here is a compression pressure/octane rating ratio that is as high as possible".........yessir, I agree that that is a good goal...a VERY good goal......and in a way: THE goal....

how to achieve that goal is where the challenges arise....

In order to have us all on the same page, so to speak......and also because I am a lazy old fart....I would suggest some reading material for all interested in this area:

go to www.theoldone.com...(the ENDYN website)..go to the articles section and read the articles on "the soft head"....also go to the archives section and read the articles there.....several hours of very informative reading.....

THEN, we will proceed....at least I will.....but I have several things to get done over the next few days--will be in and out--before I can resume my side of this discussion....

Cappy, when you read about the soft head, you will see why I lean towards a tight squish, flat tops, small CC....

And then we get to argue about valve events, EBR, charge density......

as I can, I will check in and see if there are any posts here.....but I will be tied up til the weekend....(no, not that way, Cappy....)

[945ti]

OK, I don'y have a lot of experiance with the specifics, but I got a 530 head off of a mid 80's 240 and plan on using it on my car eventually. I will keep my post short and probably not that informative, so sorry in advance.
[quote:26e216d335]most sources I have consulted strongly caution against the tendency to enlarge the size of the ports, stating that velocity through the passage is the more important thing, and that making the cross-sectional area of the passage too large in relation the the valve area would actually reduce maximum power...
[/quote:26e216d335]
This is quite true, many volvo tuners make little change to the intake channel, some to the exhaust and put in much bigger valves. One of the best mods that alot of people seem to swear by are large valves and multi angle valve grinds with the guides ground down some. Stealth mentioned this, but I just wanted to add my little bit, since this is the route I plan to go. I don't think for an amituar like me that big valves are really a concern, but I would think multi angle valve grinds and a mild exhaust side rework would improve about all aspects of teh power band and thermal efficancy. Can't really say anymore, since I have lots of theory, but at this point the rest of my information would be better supplemented with numbers and drivability effects. The 530 head seems better suited to about 9:1 pistons since it seems that the squish is setup nicely for the small cc flat top combo that stealth mentioned. The dish on the B230FT pistons alteast seems to be preventing some of that important squish from occuring.
On a side note that maybe doesn't belong in this thread stealth mentioned about ignitons may be relevant or not. You mentioned liking the small cc flat top piston narrow gap long duration spark combo. Now I don't doubt you experiance, but because of the nature of the non centered spark plug on SOHC heads and how the squish works, wouldn't it make more sense to help center the spark plug more and promote the most vertical burn possible. THis all being done to promote maximum downward velocity. I would think a larger gap sort of deal would promote this, but alot depends, and how important is that silly centered spark plug you get on the silly 16 valve head?

[poulson01]

May I?
I think Kenny, at least, knows my position in the 8V vs 16V debate so I'll leave that one alone. :rant: :pow: :slap: :bs: :owned: :pow: :rant:
One thing I'll add is that the 16v squish areas (the 16v CC has two identical lands, one by the exhaust valves and one by the intake) are much smaller than the 8v and that's where (I think) it loses torque vs the 8v.

The dished turbo pistons might *help* squish a little because of the Bernoulli effect on the A/F mixture beig shot out of the squish area. You would think that it would cause a nice swirl.

I know an engineer who researched combustion chamber burn in Universitat Zurich for years. He told me that the intake stream has little to do with CC swirl compared to squish area. The best way to get a good swirl (according to this fella) is with direct injection under very high pressure. (Sounds a bit like a DI diesel, huh).
With boost, a "bad" intake port design or low gas velocity isn't going to hurt VE very much. Just ask Porsche.
The turbo creates lots of micro vortices that help the intake stream slip down the intake runners and through the ports with less turbulence/eddies than without the turbo.

I think the basic idea is to clean the head up and make your squish area as tight as you dare. The rest of it is trial and error (hypothesis). That's why guys like Mike A aint talkin. I've tried for years to wear him down but he won't budge.

[swede242]

Then I wonder where the secret of Unitek heads are? In the shape of the combustion chamber perhaps? BTW...anyone out there ever buy a Unitek head? Was it a noticeable difference? I asked this once as a post and never heard a word from anyone.

[SquareD]

[quote:6b5cf90d85]most sources I have consulted strongly caution against the tendency to enlarge the size of the ports, stating that velocity through the passage is the more important thing, and that making the cross-sectional area of the passage too large in relation the the valve area would actually reduce maximum power... [/quote:6b5cf90d85]

With a *pressurized* (ie turbo) application, wouldn't opening up the the intake port be beneficial? You are already "artificially" increasing velocity with the turbo. Anything that allows better flow/easier filling of the bowls/combustion chamber would be a good thing, while the exhaust side would be where you need to maximize velocity, so drastically increasing exhaust port size wouldn't be so productive.

[Captain Bondo]

Wow this exploded....

Replies to Stealth:
"the one thing that limits the maximum flow obtainable is the size of the valve head......and the shape of the valve head can have an effect as well... "

Especially the size, since backcutting represents very few cons, bugger valves is something i should have done, and will do eventually.
I put larger emphasis on the bowl, proper unshrouding, and gentle short-side radii. My head flows better than many of the people with "big valve" heads are reporting.

:most sources I have consulted strongly caution against the tendency to enlarge the size of the ports, stating that velocity through the passage is the more important thing, and that making the cross-sectional area of the passage too large in relation the the valve area would actually reduce maximum power..."

Also this needs to be in raltio to the expected operating power band of the engine. IE a higher revving engine flowing more dynamically will have decent gas velocity even with larger port volumes.
But in general yes the name of the game is flow vs. port volume.


"in other words, for a particular valve size, there is an optimal cross-sectional area for the runner (the port) in order to achieve the maximum flow....if you exceed that max size, you WILL reduce the maximum power output....why? because maximum power is obtained when you have the smallest port cross-section that will deliver the flow....."

Agreed.

"let me rephrase that once more: the limiting factor for maximum flow through the port is the size of the valve head: it's area...."

Agreed, and that is what limits the max power any particular head will support, maximun availible valve area.

"after reading the info from those sources, I am definitely NOT going to get out my dremels and go after my 398 SCP......but the choice is yours...."

Damn right. After i got my head back form the porter, my first thought was "wow, i could NEVER have done this myself".

"....sounds like if I really want to increase the flow through my head, I had better evaluate the valve sizes and probably go with larger valves...or at least a larger exhaust valve....."

yes and no, the exhaust side is major crap. there are decent gains to be had there before even enlarging valves. Unshrouding the existing valves makes them more "efficient", the head "uses" the availible valve area more effectively.

"Cappy, I was pleasantly surprised when you said that you had gone over your head with a "head guy"....I apologize, because I had thought that you had just done the dremel thing.....my error....and I am glad I was mistaken; the head really looks sweet...."

Wow thanks. Ya, no way I could have done that work myself. It's just rediculous when you feel inside the ports, as if you were feeling body work, they are fairly modified and they are unbelevably CONSISTENT. That is what shocks me, every chamber and every port is EXACTLY the same. it's almost scary.



"go to www.theoldone.com...(the ENDYN website).."

Agreed. those guys are amazing. having a set of their nutty pistons made up (and a suitable cam) would be wicked.

"Cappy, when you read about the soft head, you will see why I lean towards a tight squish, flat tops, small CC...."

i hear ya, those guys are big on building engines that are nearly miller cyle engines as well, the cam bleeding pressure is a major component as well. I don't think it'd work as well with and average cam.

"And then we get to argue about valve events, EBR, charge density......"

hehe.


Replies to 945ti

"This is quite true, many volvo tuners make little change to the intake channel, some to the exhaust and put in much bigger valves. One of the best mods that alot of people seem to swear by are large valves and multi angle valve grinds with the guides ground down some."

Yes and no. The chamber unshroud and short side are the big ones imo.

"I don't think for an amituar like me that big valves are really a concern, but I would think multi angle valve grinds and a mild exhaust side rework would improve about all aspects of teh power band and thermal efficancy."

Multi angle are overrated. the key is that the transition form port, to bow, to chamber, to bore are a continuous path. Yes I have 5 angle setas but my head guy said it was pretty minor.


*
Replies to Mike (poulson01)

"One thing I'll add is that the 16v squish areas (the 16v CC has two identical lands, one by the exhaust valves and one by the intake) are much smaller than the 8v and that's where (I think) it loses torque vs the 8v."

I think it is a matter of at low rpm, there isn't enough flow to keep the velocity up, the 16v has a ton of valve area which makes the gas speed too slow at low flows.

"The dished turbo pistons might *help* squish a little because of the Bernoulli effect on the A/F mixture beig shot out of the squish area. You would think that it would cause a nice swirl."

Now THAT is an interesting thought. I could see this...

"With boost, a "bad" intake port design or low gas velocity isn't going to hurt VE very much. Just ask Porsche."

Well, it's more that VE is moved to a differne range of flow values i think...



"I think the basic idea is to clean the head up and make your squish area as tight as you dare. The rest of it is trial and error (hypothesis). That's why guys like Mike A aint talkin. I've tried for years to wear him down but he won't budge."

probably a big part of it for sure.

Relies to swede242:

"Then I wonder where the secret of Unitek heads are? In the shape of the combustion chamber perhaps? BTW...anyone out there ever buy a Unitek head? Was it a noticeable difference? I asked this once as a post and never heard a word from anyone."

no secret imo. Mike works on the 1+1=3 theory. A head gives some power, a cam gives some power, but a head AND cam give even more, the whol is greater than the sum of the individual parts. The add a header with minimum pressure drops, and an intake, it's the sum of it all.


*
Replies to D Hulting:
"
With a *pressurized* (ie turbo) application, wouldn't opening up the the intake port be beneficial? You are already "artificially" increasing velocity with the turbo. Anything that allows better flow/easier filling of the bowls/combustion chamber would be a good thing"

Pressureized or not pressurized, the engine will breath in a certain volume of air per intake stroke (the volumetric efficiency of course being the ratio of that volume to the actual volume of the cylinder).
So an engine that breathes in %90 of its volume at 0psi of boost, will breathe in %90 of its volume when the air is pressurized to 1 bar. That volume of air happens to be much denser and contain more oxygen, but it is still the same volume. The issues of velocity, and the air having "interia" still aply. Hope that makes sense.

"while the exhaust side would be where you need to maximize velocity, so drastically increasing exhaust port size wouldn't be so productive."

Yes and no, velocity of of less consequence here since there is no real scavenging happening, these days the trend is to have as little restriction as possible on the exhaust side, since the gases are just entering the turbine scroll, which will actually dictate the velocity at which the exhaust hits the turbine. large, short header primaries are generally used and the goal is to lose as little energy due to pressure loss and heat soak as possible.
Again, hope that makes sense. These are rather advanced issues that take a little mind bending. :)

[Bready]

"I think it is a matter of at low rpm, there isn't enough flow to keep the velocity up, the 16v has a ton of valve area which makes the gas speed too slow at low flows. "


:kiss:

JB
KTP

[Oskari]

stealth wrote:"most sources I have consulted strongly caution against the tendency to enlarge the size of the ports, stating that velocity through the passage is the more important thing, and that making the cross-sectional area of the passage too large in relation the the valve area would actually reduce maximum power... "

I have some dynoed fact about this. with stock 160head+a cam and 1,7 bar of boost result: 272hp

same engine, only changes were group a head and cam. Result: 1 bar of boost and 270hp.

I have to take some pictures next time i´m pulling the head..

[Captain Bondo]

Here is an original, hi-res closeup of my combustion chamber, courtesy of Dana.

I think the unshroud work/overall chamber shapre is ace, but the roof could look a lot better and is kinda ratty.



http://68.98.167.7:5555/pictures/upload/1031166447.jpg

[poulson01]

Replies to Mike (poulson01)

I think it is a matter of at low rpm, there isn't enough flow to keep the velocity up, the 16v has a ton of valve area which makes the gas speed too slow at low flows.

"With boost, a "bad" intake port design or low gas velocity isn't going to hurt VE very much. Just ask Porsche."

Well, it's more that VE is moved to a differne range of flow values i think..

That's what Mike says. Those statements seem to apply when the boost is at zero. Wouldn't you agree? I keep hearing that same old thing too: "if it works for N/A it'll work the same under boost, only better".
It's true enough but there is some "vital information" missing. Like the part where a turbo motor doesn't run worth a fart without one. I don't have a dyno in my garage but... :booty: ...my cheek-ometer is dialed right in.

The 16v heads don't have more valve area than the 8v head. Those 8valvers have huge holes compared to the 16v. It's the big valves that slow down the intake charge as it's being blasted into the combustion chamber and again on the way out. The port design, being oval as opposed to being round like the 8v, would seem to have a negative effect on flow. But every 16valver that I've ever seen has oval ports. Most of them make pretty good power, especially with a turbo. I still think that its the skimpy squish area that kills throttle response compared to the 8v. And at least they're not square :beer2:

As for VE, it's either good or bad. If it's good everywhare, then you're making lots of power everywhare. If it isn't, you have flat spots. The best way to increase VE is to add a turbo, right? So 80% of the battle is already won. A little manifold and head work (including cam) and you're about there. (Except for the years of trial and error part. I forgot about that.)

[Volvo78GT]

here's some pics of a partially disassymbled 16V head...
(mainly parts)

http://www.pbase.com/kalazdar/16v

[780GT]

Just a minor correction here... 16V heads have significantly more valve area than 8V heads do. 23% more to be specific. This is not really important though, because air does not flow through valves. It flows around the circumference of the valve.... And the 16V head has almost 48% more of that.

Also, the ports on a 16V head are not oval. On the outside of the head they are, but this is really more like an extension of the manifold. The port itself starts inside the head where the runner splits. The ports after this split are round on the intake side, and D shaped on the exhaust side. D shaped exhaust ports flow better than round or square ports.

[iadr]

[quote:bfb00776be]Especially short side radius are key at both ports, and the exhaust short side is terrible, it's almost sharp, like you could cut yourself on it almost.[/quote:bfb00776be]

Touch your finger to the flow of a moderate running water tap. The contact provides a "pivot" and pulls the flow toward the finger. It *might be* that the edge pulls flow around and into the lower half of the port sufficeiently to do quite well. Sure it's production economy, but it might have been an examined compromise.
Only my opinion, (but it *is* tested on flow bench to provide decent gain of 15-20% with 10% less overall volume) is that if you round it off you should also fill in the lower 15% of the port

[quote:bfb00776be]I would suggest that a well-prepped 8v head can perform as well as a similarly prepped 16v head....ask Mike Aaro... [/quote:bfb00776be]

I don't ever recall him saying that, and I listened pretty closely. He said, in effect, " I can get closer than you'd think, without all the fabricating manifolds and so on." Hmmm, closer than you'd think- think about the evasion in that sort of comparison for a sec. anyway not quoting Mike A or especially crticizing him. He said the same as everyone else says when the issue of 8 vs 16 comes up, nothing definitive. My collected bench figure chart shows the comparison stock to look like: int/exh @ .100, through 400, 8v being average of 398 w/o bore fixture & 405 with bore fixture. 16v head was (I believe) w/o bore fixture. Bore fixtures are the correct way but influence the numeric results far less than you'd think.
8 v : 60/39 119/81 155/94 166/111
16v : 87/81 167/159 220/194 232/196

[quote:bfb00776be]I suggest going to www.g-speed.com/pbh and reading the article on cylinder head tech, written by a guy whose company does 700hp turbo porsches....[/quote:bfb00776be]

Fantastic article, very readable. There was another article apparently by the same guy at a now defunct rice perf page. Note that the guy you reference that does Porsches, carefully explains in the 1st few lines that he only retyped the article for distribution. He did not write it.

[quote:bfb00776be]a sidenote: in the g-speed article, the author discusses multi-valve heads....his conclusions are worth the read..... [/quote:bfb00776be]

He doesn't think 5 valve has much advantage over 4 valve in motorcyle use. Beyond that you'd have to have totally misread the article to think it supports 2v/cyl. There are no known recent Cosworth engines running 2v/cyl, for one very basic point.

[quote:bfb00776be] 16v squish areas [are] where (I think) it loses torque vs the 8v. [/quote:bfb00776be]

Given cams properly selected for the same purpose, and equal compression, I believe it would be extremely unlikely that the 16v would lose torque. Feel free to provide figures or even theories and impressions to back up a comparative loss. A failure to gain is not the same thing as a loss.

Two rules of thumb from a guy who built his own 1000+cfm bench, went to David Vizards classes, and used the bench a lot over a period of years- he now runs a vinyl graphics outfit. If that's not a reason to hate ricers I don't know what is. Anyway, rule of thumb in playing with various things including intoducing machinists blue into the airstream was that the short side of the intake is always the place to widen or otherwise remove material. He never ran across a head having highest flow on the intake port roof. Not once- Sounds like a pretty safe rule of thumb. On exhausts the opposite occurred- flow is always on the roof. You need something like a 4 inch radius, where there is usually a 1 inch. The flow hits the flat of the roof where to bends to horizontal. Articles on the latest NASCAR heads, like the McLaren Ford, seem to bear this out.

[Anonymous]

Then I wonder where the secret of Unitek heads are? In the shape of the combustion chamber perhaps? BTW...anyone out there ever buy a Unitek head? Was it a noticeable difference? I asked this once as a post and never heard a word from anyone.

I have bought a Unitek head from Mike. It is in my opinion a work of art. The intake and exhaust ports are a straight smooth shot into the combustion chamber. All the ports are balanced as far as shape and size. I had the bigger valves added that fit nicely in the smooth combustion chamber. I am building an engine with this head and soon to have a short block. All to go into the 940t with a supra 5 sp tranny. I have not run this head as of yet but I will tell you that it is a class A1 job. It looks like it will run standing still. I hope to have the 940t up and running sometime this spring. I will keep you posted if you like. Mike has always been helpful to me.

bis später, jt

[swede242]

FINALLY! Someone has one to ask!

I look forward to hearing all about it!

:D

BTW....how much $$$ did it set you back????

[G96nt]

All I can Say, is "thank you"

and that although I have The ideas,a nd principles in my head, I haven't the technical experience And Can't Explain things As Well as I'd like.

I still think I'm going to go 16v when I have the time/money

the reason isn't *JUST* in airflow, but Also adjustability, of mechanical timing per cam and the ability to run different cam profiles per Side As well!

it Also seems that the 16V with it's better air flow and possible higher power-curve would be more of a 1/4-mile Car, Allowing for higher overall CFM in higher RPM wich allows for low static Compression, and high boost-amounts; Where the 8v, and it's torque-inducing "choke" would be the route to Take for a nice low auto-x-type torqu-curve And low-boost applications. and most-likely a higher-compression setup.

the 2.1L I intend to build will likely be stock-compression (barring changes in CC volume in 16v head) 16v with a mild porting/valve-seat refreshing and full 2.5" piping from air-filter to "muffler" more of a "high-rev" heavy-breather

maybe I was just spoiled over in the 4g63 world having a factory head that can flow As Well as DSM's Do?
is the thought process I've learned over there not nearly the Approach I should be taking here?

thanks guys...

and... um.... buy my FMIC! :wink:

[Captain Bondo]

"Touch your finger to the flow of a moderate running water tap. The contact provides a "pivot" and pulls the flow toward the finger. It *might be* that the edge pulls flow around and into the lower half of the port sufficeiently to do quite well."

Even rounded, the short side radius has this effect. Interestinly as you say with the finger thing, your finger is rounded, and water is drawn "around", swing around almost like a slingshot, that surface. if you try it with a butter knif with one side blocked off, it does not work nearly as well.
Also, it is on the roof og the exhaust port, and as you mentioned, that's where the flow is when exiting the chamber.

"Only my opinion, (but it *is* tested on flow bench to provide decent gain of 15-20% with 10% less overall volume) is that if you round it off you should also fill in the lower 15% of the port"

I can see this for sure.



"I don't ever recall him saying that, and I listened pretty closely."

Agreed the 8v was always a bang for the buck thing.


"He doesn't think 5 valve has much advantage over 4 valve in motorcyle use. Beyond that you'd have to have totally misread the article to think it supports 2v/cyl. There are no known recent Cosworth engines running 2v/cyl, for one very basic point."

Well , there is definitely a point of diminishing returns, since you can keep adding effective valve area and included diameter within a given chamber size, but as you have more and more valves, the valve heads get closer and closer to the same diameter as the stems.



"Given cams properly selected for the same purpose, and equal compression, I believe it would be extremely unlikely that the 16v would lose torque. Feel free to provide figures or even theories and impressions to back up a comparative loss. A failure to gain is not the same thing as a loss."

I think he meant bottom end, or "low flow" torque due to poorer ve at low flows due to slow gas velocity.

"Two rules of thumb from a guy who built his own 1000+cfm bench, went to David Vizards classes, and used the bench a lot over a period of years- he now runs a vinyl graphics outfit."

LOL. Rice comments taken with great enjoyment, as well as the rules. they certainly make sense to me.

Appreciate your comment Ian.

And Ryan thanks for the valve area numbers, i was worried i was going to have to work it all out. :)

[Anonymous]

what a day....just dropped in.....

interesting....ok....if y'all wanna make this a debate of 8v vs 16v, that's fine with me.....I am not interested.....if my comment about 16v was cavalier, the error is mine....I was expressing my personal opinion, though, and identified it as such.....

there ARE features of the 16v approach germaine to the discussion that I THOUGHT was in process here.....good and not so good features.....worthy of consideration evaluation and appraisal.....

I do not HAVE to spend upwards of an hour or more--at least-- on typing--which I HATE--to try to organize and present a topic post reply with observations for discussion, to present to people who I do not know; but because of an alleged common interest in turbo'd bricks AND N/A bricks, I take the time to try to be of assistance to their alleged pursuit of intelligent performance enhancement. for d##n sure I dont hafta.....

I most definitely do NOT know everything there is to know on the subject.....and even more absolutely definite is my knowledge that most here are in the same boat....

SO...like I said at the beginning of this post: if y'all wanna make this a 8v vs 16v, mine is better than yours, 3 semi-sentences and an emoticon, post count boosting, I can pee higher up the tree than you can heehee kind of topical non-discussion.....that is fine.......I will dee-cline the inn-vite...

I can carry on my discourse privately......dont hafta gotta do it here....

I wanted to broach the subjects and topics Cappy raised to help all of us understand better what we 're doin......these ARE important....
those who did inconvenience themselves enough to actually visit the links I offered, and then actually read the articles suggested, probably were confronted with ideas and concepts that they had not thought of or in that way......and hopefully, for their own benefit, realized that these ARE important subjects.....

I also hoped to inspire some thinking and thereby generate questions and comments that all involve could consider and evaluate......and reply to in a civilized manner, explaining and corroborating their positions disagreements or conclusions.......pi##ing contests are NOT educational....nor recreational...if'n you're into the golden shower thing, fine.....I ain't....and ain't int'rested....

you got a point to make....fine....state your case...fine...express a personal opinion...fine...offer some info or evidence to support your case...more fine...say why it is on topic....or how you think it is on topic.....or related....or relevant....even more fine....I aint got no prob with that......

think about it guys......I got more to do for a coupla days.....I'll drop back by prob'ly Sat....to see who wants to do what....

COMMENT: (apparently off topic now).....

Cappy, you did reduce the squish a bit.....and I am gonna hafta disagree with you on the exhaust valve size thingy......a few aspects to consider....but "that" will have to wait.....

but that is ok...I do know WHAT I am doing....I do know HOW to do it......I do know WHY I do it....and I can DO it....

[Captain Bondo]

Holy crap that was a wicked post.
Agreed, my intent was not to start a 16v vs 8v thread at all.
This is really guided towards what to do with my 8v next time I pull it off.
I probably bring up the exhaust valve issue just because I neglected to get big valves. ;) I do know they are a good idea, and that all tuners do it.

Bigger valves are on the shopping list. With thinner (3 or 4mm instead of 5) stems too and bronze guides.
The is some loss of quench area, but I think the unshroud/vs quench loss of ok.
If you check out the pics of Dave Barton's head, you'll notice a lot more quech loss.

[Anonymous]

I screwed up...

I did what I get upset with when others do it: answer off the cuff, rashly, and without patience to allow something to settle out...

the swerve into a 8v/16v pi##ing contest was sorting itself out....patience on my part would have been rewarded....

I stand corrected on my error of attribution of authorship....hopefully, my error will not diminish the consideration given the material in the article....neither pro nor con on multivalve; I found the observations of the author thought-provoking, and worth reading....

the one person I must apologize to directly is Bready....your posts were not guilty of what I got all PO'd over....

you were expressing support for the topical discussion, your complimentary words to me I did appreciate, and feel unworthy of now....

your addition of humor was well-meant and timely....further evidence of support for the efforts being made on the subjects.

As I stated at the beginning of this apology, if I had only waited, everything would have smoothed out anyway....in actuality, most of the points being made do tie in....and were not deserving of any vitriol on my part.

I screwed up: I copped an attitude; I launched......I apologize.

[Anonymous]

to undo my digression, let me do the following:

G96nt.....you bring up what I consider to be a real plus of the 16v: the ability of being able to vary the valve overlap of intake and exhaust....and the higher flow of the multivalve arrangement would lend itself for the use you see....

Poulson01.....I agree that the 16v is squish challenged....not sure just how much that drawback affects torque....

the adage of "if it is good for N/A, it's good for boost, only better" (approximate paraphrase)....I do have to agree with your take: not always.....

swede242.....I share your interest in hearing more from a UNITEK head owner.....

iadr....correct authorship noted/my error there acknowledged......I didn't take it as an endorsement of 2v over 4v......the observations made were what I found of import....to be considered with other sources to aid evaluation....

the rules of thumb you mention are valid....have read similar conclusions elswhere....good food for thought.....

your running water analogy is very good.....helps one to visualize what actually goes on in there....

I was not trying to put words in Mike Aaro's mouth; I do not think I was mis-quoting him.....I do not remember where I "heard" that....a post here or in an email....my error for not having that source at hand.....but Cappy's comment clarifies what I meant and was also attempting to convey what I thought that Mike meant in his comment: that for a given use, the 8v could be at par with a 16v--that use being street use.....was not trying to mislead or infer improperly otherwise; sorry for any vagueness.....and if it turns out that I was mis-quoting Mike, my apologies to him. I won't repeat that error.

Cappy..... whether or not the squish was reduced or by how much was not that important....I was razzin' a bit.....the choice of flow improvement vs shape is one with many factors to prioritize....cost/benefit kind of thing....for the use and operational parameters--the "animal" style--that you have stated, I can see why you opted for the flow side......not pooh-poohing that at all......but debatable, yes?

[Bready]

AH! GROVELING!!! DIRECTED AT ME NONE THE LESS!!!

This is a banner day indeed! :beer:

However - I actually had only a small peripheral role in this thread, and that role had nothing really to do with the topic at hand. I beleive the confusion stems from the posts bearing the user name "JTB", who is not in fact JB (just as V-ready is not B-ready).

Just a clarification. I tend to agree with the 8v being the most cost effective avenue for most of us, with adequate potential to 400HP+. Nothing wrong with the 16v approach, just not going to be the route most on this board are going to pursue, and doubtful that that will result in any performance set-backs for even the more lofty HP goals most of us kids here on the board may have.

Again great thread.

JB

[swede242]

I can say this....3 times I have exchanged emails with Unitek about the advantages/do-ability of a 16v motor.....the replies were always the same (a bang for buck extreme inefficiency), but the last one included a fairly detailed account of the costs involved.....about $10,000US to be exact and ALOT of fabricating. Now, considering the knat straining that goes on here with pittance like "boost controllers" WHO is or CAN shell out the 10G's for this? I honestly have no idea WHY we even waste the time to discuss it. I understand there are principals to learn and apply here that do apply to both 8's and 16's, but if that be the case, why don't we discuss the shortcomings of the redblocks and the "possibility" of casting our own? I get ALOT of "make-me-think" knowledge from stealth's posts and hate to wade through million-dollar fantasies that lets face it, most if not all of us will never have the $$$ to throw at.

This is why I post nonsense like "weight reductions" through the removal of vital components :) I look at removing a back seat in a 4,000lb car like a 400lb guy washing down his large pizza with a slim-fast shake....what's the point? :)

Positively no tantrum here, all just my own personal opinion, but I just honestly enjoy posts like this....makes sense of so many others.

:mrgreen: Peace.

[JT]

FINALLY! Someone has one to ask!

I look forward to hearing all about it!

:D

BTW....how much $$$ did it set you back????

I have a 530 turbo head that I got from Unitek. I did the phase 4 option with the bigger valves, new guides upgraded valve stems, Head set, labour, used '97 intake manifold, and phase 4 cam. It cost me just under US $2500. I have some other things coming from Unitek but I was told that this combo should make about 175 HP in NA form before boost comes on. I am planning to do step upgrades... Turbo, fuel, clutch, ignition, exhaust, etc... I no deed have much work to do. I also want a daily driver. I call it Operation Grocery Getter. I am looking to gerenate 300+ HP. Stay tuned... I am in the early stages...

Bis bald,

jtb

[Captain Bondo]

could any unitek head owners post some pics of these beauties? Especially the combustion chambers.
I'm terribly curious. :)

[swede242]

Yes, and theres nothing like getting groceries in half the time!!!

heh heh

MAN.....I'm just FULL of envy at this point......

:help:

[poulson01]

[quote="stealthfti"]Poulson01.....I agree that the 16v is squish challenged....not sure just how much that drawback affects torque....quote]

Well, I've NEVER claimed to be any kind of expert on ANYTHING but according to my friend, Jerry the rocket scientist, (who really only confirmed what I already suspected) swirl is esential to a good burn. Now if you think about it, there should be plenty of swirl at high RPM no matter what the CC or ports etc look like. Right? Low RPM is where the squish effect is important because the speed of the gasses is probably relitively slow. Again, I'm not an engineer. I'm not even a mechanic anymore. Anyway, Jerry told me that the intake charge swirling as it enters the CC is not enough to fully mix the gasses (which did surprised me). Looking at the 8v and 16v heads next to each other on the bench, I can sort of visualize what happens when the piston comes flying up at those squish areas. I have a hard time visualizing the 8v head filling better than the 16v head, even at low RPM and even if it did, our turbos start to spool up by 1800rpm +/-. You can definately feel the 16v motors bog a little, even though the rev fast and growl really nice. I *THINK* it's because of the small squish areas of the clover leaf pent roof CC of most 16v engines. The 8v wedge (not really a wedge), even with 7.5:1 feels torquey in comparison.

I am surprised, again, by the 23% larger valve area of the 16v head (I knew the circumfrance numbers were much bigger. That was part of my point). I didn't think that much was physically possible. Thanks for the info 780GT. You won't mind if I varify it on my own cylinder heads? :wink:

[Captain Bondo]

I can see that now mike.
Better fuel mixing and faster burns mean less total timing is required, and conversely better squish/quench/swirl would also mean faster burns, or more consistent burns to allow the use of more timing, the more complete burns possible via better fuel mixing would be like having more advanced timing at low flows, and therefore more bottom end.

Is that what you mean? i could see that anyways, how big of a factor it is on the grand scale I'm not sure, but I could see it...

[780GT]

Don't know if it's worth anything, but for those that are interested in a good look at a 16V combustion chamber, I have done a little work on mine. They are not polished up yet, and no ceramic coating in this shot. There is not much to easily improve here, just cleaning up casting flaws and removing sharp edges around seats, etc.

http://bertone.wynott.ca/images/16v/chamber-work.jpg

[iadr]

Sorry stealthfi- my post was negative, that was the frame of mind the thread as a whole had put me. I thought a few too many half thruths and confusion were in action.
I'll make an honest effort to do a more constructive post this weekend.

Kenny- stock valves are 8mm stems. I very doubt you want to go below 7mm. We're talking maybe 10g off a valve in weight at most. Some possible compromise in guide wear, even allowing for the design not creating OHV type side loading. The 4.6/5.4/6.8 Fords use 7mm stems. I don't have dimensions handy, but know their valve springs work in pre75 Volvo engines. Don't know of any street use of 6mm in a car. Kibblewhite are very easy to work with for custom stuff, and IIRC, some Harley bike engines use valves that work.

[swede242]

HEY KENNY - what (if I might ask) did your head work set you back $$? I'd love to find someone who understands the theories discussed here to do it right the first time.

There's a machine shop nearby me that does excellent work...HOWEVER, their forte' seems to be in SB race engines. When I mentioned not grinding my turbo's valves and lapping them in by hand, you'd thought they were dogs and I'd just hit a high pitch whine.

Worries me.......

[poulson01]

... more bottom end.

Is that what you mean?

Yeah, that's pretty much it. According to my friend, it is a huge factor (I seem to remember Mike A "suggesting" once, how important a tight squish is). I happen to concur. Like I said before, the fact that the intake stream has little swirl value did surprise me but imagine what happens when that piston comes whipping within a couple of mm of that flat part of the head. Those gasses must come out of there with FORCE! The intake stream could never produce that much swirl.

[JT]

could any unitek head owners post some pics of these beauties? Especially the combustion chambers.
I'm terribly curious. :)

I do not have a digital camera but I will borrow my buddy's camera and get some pics of it on here by Wednesday. :wink:

Bis Später,
jtb

[Captain Bondo]

LOL thanks Ian. I get confused easily these days.... I think that the stems on Mike's were actually 5mm. maybe JB can verify or another Unitek guy? Maybe that is race.. i dunno, I just remember the idea of thinner stems sounding like a great idea, both for weight and for less flow restriction around to the other side of the valve (?).


Swede,
my headwork was a little over $900 Canadian including new intake valves and seats and other little things. The shop who did it mostly builds Mitsu/Honda/VW stuff, rice. More relevant than SB Chevs though i think.
you can check them out at {url]www.lr-racing.com[/url]

Mike,
definitely on the same page man!

JT,
those pics would be AWESOME! Man that'd be so cool!

[Mike]

The format of the combustion chamber is, lika almost all other aspects of the combustion engine, a compromize, and it obviously has to connect to the rest of the combination...

Issues to contemplate on a non-oem application might be (that applies to each & separate combo of valvesize vs bore vs compressionratio vs etc):

* Quickburn features a.k.a. burnrate/burnratio

* Optimum format in order to enhance the VE

* Detonation/pre-ignition features

* Combustion surface area vs combustion efficiency

* Etc

__________________________________________________ ______

BTW: For those interested we've now have a 2003 update on our info-files regarding:

* Theory (including the ever important art of project-planning...)

* Gr11/Heads

* Gr24/Engine kits

Format: Zip + PDF.

Just send a e-mail and it'll be returned with the attachments of your choice.

Best regards

Mike

M.Aaro@mail.bip.net

Luleå (northern part of Sweden)

(New info-file versions: Gr11/Head & Gr24/Engine-kit & Theory [all Zip + PDF)

[Anonymous]

dropped in to see.....

Bready....hope you enjoyed your banner day......but don't be expecting more of them from me....heehee...

iadr.....I don't quite understand why you would get a negative attitude....oh yes I do!!...

I do not try to do the oracle from on high routine: the 'this is so because "I" said so'......the immediate and justified reaction would be: 'WTF are you?'....

in trying to avoid the oracle syndrome, it does become difficult to avoid the generalities/vague/fogged glasses pitfall.....sorry if I fell into that.....

I enjoy your posts; have looked at the pics etc you have up; and admire your efforts.....just because your goals/Approach to Perf may be different from mine does not make me think any less of them....quite the contrary....your Approach requires serious sustained efforts that I respect; but am not inclined to also do: my Approach to Perf is different......I am not in the need for the high rev capabilities.....but I still appreciate the efforts of those who are; and listen, and learn from their reports......looking forward to more from you...

at no time was I intending to belittle 16v or efforts to use that tech....when I get to part 3, that will become more clear....

780GT......Ryan, nice pics....I will be referring people to look at your pics to sustain points I will be making in part 3 on the 16v CC.....

Cappy and Poulson01.....more in part 3, but this now: a better burn rate and shorter burntime need LESS ignition advance, not more....and that leads to other benefits......

Operation Grocery Getter.....I LIKE IT!!!!

Mike....thank you for your comments; it IS a package deal kind of thing.....everything does have to work together towards the same objective...

part 3 is in the works....more then.....back to the salt mine!!!

[Captain Bondo]

"Cappy and Poulson01.....more in part 3, but this now: a better burn rate and shorter burntime need LESS ignition advance, not more."

Yes. faster burn means you don't need to start it as early.
What was meant was that a faster burning head at 10 degrees advance will have more complete burns than a slower burning head at 10 degrees, and have more bottom end.

IE a fast burning head at 12 adv might feel like a slower burning head at say 15, just for argument's sake.

[poulson01]

I know what you meant Kenny and I hope your questions have been iluminated for us. I think we can sum up (over simplify) the whole thread by saying that you need a good squish surface as well as easy access for the intake and easy egress for the exhaust. As you make the CC larger by hogging out extra aluminum to facilitate this, you increase burn time as well as decrease your squish area. So the point is that there is a balance which you can shift around depending on what you expect the engine to do. (Kinda like any other mod) With my 16v, I'm almost tempted to remove the squish areas completely and have a clean screamer but it's a silly idea. I know I need all the squish that it has.
I too would like to see examples of the famous Unitek head job. I know you can't get much more than a tease from a photo but I am, like all of you, curious in an analytical way about things I can't afford.

[iadr]

Stealthfi- note I said the thread as a whole, not your post. As far as my different approach, I dunno- I work as a shipper receiver for a race parts distributor. Being able to grab parts that I see available, I may sometimes give the appearance my priorities are backwards- ie some more normally expensive parts get used in less critical areas, and cheap parts used in more critical areas. It does give me access to people to ask (within their patience level). In the summer if I stay late, I can hear through the front a back doors of the warehouse, 3 separate dynos all located within a few blocks, doing runs . My 2600cc b23E was balanced at the cost of getting pizzas for the crew (& don't get jealous because there are a lot of big boys at that shop :wink: ) at a machine shop that did a Cascar (CDN Nascar) champion's motor. All that said, the job doesn't leave me with anywhere near as much money or free time as I'd like. As far as the more 'considered' tone of the post, as a Canadian, that didn't particularly grate- we are -Kenny excepted (sorry man, :lol: couldn't resist )- more careful of our audience's egos and so on. Also, IIRC, you have at least 10 years and some engineering background on me.


As far as the 16v quench, Honda was the first to get Ultra Low Emissions Vehicle status for a gas engine, using a chamber similar to the Volvo 16V, but with quench areas extended between the valves- might be worth fill welding the Volvo head to copy that.
FWIW, I seem to remember hearing that because of the relative high RPM's and the spindly connecting rods, stock Honda quench was not set up very tight, so that isn't the secret.
I tend to believe that a pentroof, limited quench chamber can provide all the practical things as well as perf. If nothing else convinces, maybe the observation of big manufacturers spending the extra R&D and manufacturing costs to go to 4v on bread and butter, emissions-type cars will.

As far as quench in general, & on 8V, if we agree that on (as Mike A would call it) an "optimized" engine, it's smart to reduce the quench clearance dimension by about 40% over the volvo .06"-ish, and say that because of the fluid dynamics involved that creates 50+% more squish-effect, we can come to 2 subjective conclusions-
1/ unless we see a night and day difference, squish is not the be-all and end-all some posts in this thread taken out of context would have you believe.
2/ we could remove lots of quench area, duplicating the 405 chamber and then some (I'm thinking Dave Barton's pics here), and still have significantly more squish-effect than stock.


Swede242, I'm sure 10k is taken out of context for use here. Paying someone to do everything, and starting with a stock car and going to a 350+ hp one, sure, easily, but to do a conversion from 8 to 16v heads and manifolding, in itself, no. If you hang around the Ford guys using the Volvo head on their motors, you'll find that the agreed price for a head/manifolds/small parts set is less than 400. They are doing complete conversions for less than half the 10k figure. The yahoo group 230016v is a good place to watch. Mike Aaro posts there. I know a few of the more determined T-brickers are watching 2.3 Ford stuff in general. For Volvo use, the intake works 'as is' on 700's, & for 240's can have the throttlebody moved to the end. Exhaust is b204ft or custom, which can run into $'s you farm it out. Most anything else like an EMS setup would have to be changed to accommadate high HP level anyway. Check out the Swedish Turbo Performance club, and so on. There are many people who can weld and frabrcate who could do (and some who have done) an 8 to 16v swap conversion "in itself" in a month of evenings and partial weekends. 10k- sheesh

Kenny- AFAIK, if you have significant air flow across the back of the valve, you have a problem. It should 'cone' out as evenly as possible. Why people do pay close attention to the opposite side of the chamber is because the fuel droplets have far greater inertia than air, and they may tend to move across the back of the valve.

Ok, now I feel a bit caught up.

I'd like to paraphrase a Vizard article that appeared in Circle Track magaizine last fall.
I have photos taken of the printed page, but no good host. Email me @ iadr@hotmail if you want a copy. I'd intended to use the same host I used to post to the showroom a few months back but forget how. I also have pics of some experimental porting I've done that I've had flow benched.

1/ if you examine restriction, one way of quantifying it is to measure gas velocity at different points in the port. At low lift, it's obvious that the seat area- the annular gap created as the valve opens- is much smaller than the area of the port, so that is your restriction, your highest velocity. He makes up a line graph comparing seat velocity and port velocity. On his example head, the priorities cross at .390" valve lift, the port becoming the equal or greater restriction above that. Obviously this implies one should use huge valves and small ports. However if one goes too far that direction, reversion possibly becomes more of an issue, not sure of any other disadvantages. My copy of the magazine still has my pencilled-in "why" next to the paragraph stating that one should not go overboard in the direction of huge valves-small ports. I would think doing so would tend to duplicate the flow@lift curves of a 16v head- not necessarily a bad thing. Anyone's thoughts?
2/ There are clear rules of thumb as to ideal port cross sectional area for a given duty/rpm range/displacement. To find port cross sectional area, cc the port with the valve closed, then find the average cross sectional area by measuring the port length in centimeters and doing the math. To measure port length use a wire bent to the centerline of the port, or average the lengths found with a wire fitted tightly on the roof and the floor. To use the provided rule of thumb formula relating to displacement and rpm given by Vizard, convert the port cross sectional area to inches.

If you follow domestic performance heads, you know that heads are sold/rated by intake port cc's, which cannot be compared except among a given engine family.
Converting to area allows comparisions between Ford/GM, and between big and small block, bewteen import, domestic and even motorcycle, greatly expanding the pool of data and experience.

3/ back to low lift flow. A 30 degree (as opposed to 45 deg) valve seat helps make the gap created by the opening valve increase faster due to the geometry involved. Because this enhances low lift flow, it makes the cam appear like it has greater overlap relative to its duration, ie tight lobe separation. In budget N/A applications, this makes it possible to use stock cams (K, VX) having wider lobe separation (low overlap), and realize performance gains. Even if the 30 deg seats cut peak flow, having it increased at the end of the exhaust cycle and beginning of the intake cycle has potential for VE increases. This applies only to N/a and turbos having a better than 1:1 EBR.

[Anonymous]

iadr.....excellent post....lots to chew on and respond to....thank you....that will pro'ly take another post....or two...or three..

part 3A: is squish good?

because the terms are often interchanged, some definitions are in order for clarification and to reduce confusion:

QUENCH: aka quench zone or quench area.....refers to areas or zones or locations in the combustion chamber that impede or prevent combustion; usually in reference to a cold spot, or to a restrictive area, such as the space around the sides of the piston above the upper ring....air/fuel mix can get in there, but it doesn't burn or not very well....can also refer to a place where the air/fuel mix is either too lean or too rich to support the burn......

SQUISH: aka squish area or squish zone.....and it is also the physical action of squeezing out the air between two surfaces as they approach each other....

squish area refers to the areas of the surface of the cyl head inside the bore that come into a close proximity to the corresponding areas on the piston crown at TDC.....

squish (the action) refers to the pressure wave and turbulence created when we bring these 2 surfaces to close proximity....

example of squish action and resulting pressure wave/turbulence:
......place a candle on a stable surface; light the wick; with a cute little flame going, hold your hands about 3 inches above the flame and about 3 inches apart like you are going to clap; clap.....the flame will go out if you bring your hands together quickly enough....

SIDEBAR: I will not be held liable in any manner whatsoever because of some klutz who can't light a candle and/or clap the flame out without burning down the building or burning themselves or catching themselves on fire.....if in any doubt as to your ability to perform this experiment safely, hire a professional.....

IF you were successful with the experiment, then you have duplicated SQUISH.....you get 2 stars.....

we get squish action by having squish areas in the combustion chamber: areas where the piston crown comes into close proximity to areas of the cylinder head at TDC....

BENEFITS OF SQUISH:

turbulence of the air/fuel mix in the combustion chamber improves the mix...the homogenation of the air and fuel molecules into a more uniform burnable commodity....squish increases the turbulence....which can make the burn more likely to occur(ignition probability), and occur faster--faster burn rate....which means a shorter burn time: less time that it takes for the flame front to complete combustion of the air/fuel mix....

the squish areas also help to shorten the burn time by temporarily reducing the size of the combustion chamber.....by temporarily creating quench areas that do not support the burn....

This needs some further explanation of some other factors and their interaction......

BOUNDARY LAYER COOLING: aka PFM, or what really makes squish areas nice to have......

above the surface of the piston crown, and below the cyl head metal surface, a layer of cool gas forms--yeah that's why I said it was PFM--....it's a layer of gases that are cooled by the proximity to the metal surface...it is about .020in in depth.....yes, it is real.....at least, that's what I've been told.....

back to squish areas:

if we set up the piston to cylinder head clearance--at those areas of close proximity--to have a clearance of about .040in, two things come into play.....we get really good squish action: whoosh!! and we bring the boundary layer cooling layers together, or just about together......this results in a couple of things, both good.....

I forgot to mention that the boundary layer cooling layers are almost quench areas....by that I mean that the gases there are cooler, and do not support the burn very well...defacto quench, sorta kinda.....(I expect to catch some grief for that generalization, for sure)...

Anyway, if we set up the squish areas to have a clearance of .040in, we basically have no room between the surfaces for a burnable mix, the boundary layers and the squish flow take care of that.....this results in a smaller combustion chamber, temporarily....that is until the piston moves down far enough to restore sufficient clearances to let the burnable and burning mix back in.....this temporarily smaller combustion chamber is often referred to (by people like me, anyway)as the burn chamber....

smaller combustion chamber, shorter distance for flame front to travel, shorter burn time....good.....

a side benefit of the boundary layers getting together: increased piston surface cooling through proximity heat transfer....(how's that for techno-babble?)

OK!! BUT HOW DOES THIS HAVE ANYTHING TO DO WITH DETONATION--OR REDUCING DETONATION??!!

I am so glad you asked.....

when we do the smaller burn chamber thing by getting the bounday layers together, we reduce or eliminate what is known as "end gas".....that real thin layer of burnable mix far away from the flame source.....if that layer is there, as the flame advances, the end gas can be heated --and compressed--to its auto-ignition temp....and go BOOM!!....if it's not there, it can't go boom....

(YES, there are some more reasons for less detonation...we'll get there)

in part 3B, we will get into the CC layouts of the 8v and 16v....and discuss them in context of squish etc.....and get into "optimal" squish...that will be fun...

[Anonymous]

Nice. So the next question would be: What would be the benefits of having a perfectly hemispherical CC with no squish area over a wedge? I've had motorcycle engines open that had about as perfect a hemi head as you could find. The old Chrysler hemis had no squish area either. There must be drawbacks to having a squish area. I need to get the head of my Miata engine. It is said that this is a ping proof engine.

[Anonymous]

There are drawbacks to going overboard on squish areas...coming up in further parts...

re hemi CCs....that configuration has its strengths and weaknesses....a google search will yield a plethora of info on that....back in the days when one actually did see hemis on the street as daily drivers, 100+ octane leaded fuel was about 30 cents a gallon; which made the 8 mpg endurable....only one hemi driver I ever talked to got over 10 mpg...and he had to rejet the AFBs and "drive like a little old lady" (his words) to do that....

in those days, I was driving a '68 Charger RT 440 Magnum/torqueflite/3.23 posi.....10.5mpg whether doing 65 mph or 140 mph.....and I did 140 (4400 on the tach)in the CA upper mojave desert for up to half an hour at a time....them was the days...

hemi heads are nice....volvos don't have them.....they have better: the pent-roof multivalve....aka 16v

volvos also do not have wedge heads.....the SOHC 8v valves are prependicular to the deck, not tipped: no wedge.....MAYBE the OHV 8v B20s have a wedge....been so long since I looked at one, I forget.....

not trying to sound smarta## on this......just that hemi CCs are enshrined in myth and legend....and the drawbacks and problems to get the most out of them are often overlooked.....further google on hemi CCs in cycles will show the problem areas encountered....there are drawbacks...hemis aren't the do-all end-all even in bikes...

and yes, there are lots of engines that were designed with no squish....areas or action... and ran fine....hopefully, as the discussion progresses, the value of squish will become evident....

[poulson01]

There are drawbacks to going overboard on squish areas...coming up in further parts...


Well!?......Spill. :?:
What does the engine gain when you grind off some squish? Better burn up top, right? Sacrificing low end?
What happens when you have too much squish? Flameout, right? Proly runs great down in the low revs? I'm just guessing. I've never heard a discussion on this and I'm ready for the "further parts". By the way, I had a Dodge Polara with the same goodies. :twisted:

[Anonymous]

poulson01....Mike, thank you for your interest.....

I will "spill" as soon as I can....am working on part 3B and some comments and questions for iadr.....and I want to take some measurements on some shortblocks I got on cradles.....it will pro'ly be the weekend before I can get all my "stuff" together for that.....

by the way, did you try the candle experiment? and no, I won't ask if you had to hire a professional....:wink:

[Canuckvolvo]

I burnded my fingers....:yikes:

Just wanted to say thanks for the posts stealth, very informative! I PLAN on building up a B23FT sometime soon, have all the components, just missing the time and inclination (B21FT is running fine for now) and when the time comes it'll be good to know how much squish, squarsh, quench or whatever to aim for!

looking forward to 3B...

[poulson01]

by the way, did you try the candle experiment? and no, I won't ask if you had to hire a professional....:wink:

:owned: I ran a mental simulation and no, I can't afford a professional.

[JT]

could any unitek head owners post some pics of these beauties? Especially the combustion chambers.
I'm terribly curious. :)I have some pictures of the Unitek Head but I do not know have to get them on the board. If you like I can sent them to you off line.

[Anonymous]

A further clarification of terminology is in order.....and it will help explain some things...

It was strongly brought to my attention that I and others here have erred: in the use and mis-use of the term SWIRL....

SWIRL....is a rotating volume of air.....visualize a tornado...that occurs in the intake port as the air passes the intake valve AND occurs inside the cylinder as the piston goes down on the intake stroke......

this rotating column of air (and fuel) happens....whether we want it or not.....regardless of intake valve position....it just happens....all by its ownself...

....when this swirling air is compressed into a smaller volume and into the confines of the combustion chamber, it is torn apart into bunches and bunches of itty bitty teeny tiny tornadoes.....and makes turbulence....

...so even if we do not have any squish areas to make squish action, we still get turbulence.....

SQUISH.....the pressure and shock waves resulting from close approach of the piston to the cylinder head also makes turbulence.....essentially independent of SWIRL....

SO....IF I HAVE SWIRL CREATED TURBULENCE, I DON'T HAVE TO HAVE SQUISH, RIGHT?

maybe; maybe not......the key is a thing called "turbulence intensity"......and the more of that you have, the better off you are......and SQUISH ups the turbulence intensity....

If you would like to see pictures of swirl, then visit www.herc.musashi-tech.ac.jp/shudo/esd/Data/001/C85_P413.pdf

.....a very interesting paper presented to the International Symposium on Diagnostics and Modelling of Combustion in Internal Combustion Engines (COMODIA 1 1985).....

...and if you read the article, you will see that what I bring up about swirl is substantiated....and then some.....

...what this means is that debating "squish vs swirl" is essentially a non-issue...they are essentially independent of each other....

AND that we need to make sure that we have our terminology correct....mea culpa....

....one thing that getting the difference between SQUISH and SWIRL straight is that those motors that do not have good squish still have turbulence....just not as much as they would if they had some squish areas....

There is another article, this one from COMODIA 3, 1994, that I had intended to pull a bunch of quotes from to substantiate my position that "squish is very very good"....

....instead of that, and boring the heck out of people, here is the link:

www.herc.musashi-tech.ac.jp/shudo/esd/Data/003/C94_P001.pdf

...that's a big one; it was the keynote address of the symposium....if you want to see pictures of the spark plug firing and generating the flame kernel, they're there.....if you want to see pictures of the flame front, they're there......

.....and if after reading those articles, and others from the 4 symposiums, you still belittle or pooh-pooh the need for good squish areas and action, I can not offer any more evidence, nor would I feel inclined to try.....

...BUT, if you SEE it, and would like to see and hear about ways to increase squish in 8v AND 16v, we can get into that in part 3C....

...oh, and yes, I can offer a way to illustrate too much squish....

...happy reading, thinking, comprehending, and analyzing.....it's a good way to stay out of trouble...

[Volvo78GT]

Pics of the Unitek : http://www.pbase.com/kalazdar/unitek_phase_4_530

[Captain Bondo]

:eek: :eek: :urgod: :werd:

THANKS FOR THE PICS JT!!!!
And thanks to kal for putting em up!!

So it looks like mike is increasing the squish height (decreasing the distance from piston to deck) and decreasing quench area in the name of better flow.

is it just me or are those combustion chambers HUGE???
And Stealth was picking at me for haveing lost quench area... ;)

Now what?
I hear what Stealth is syaing, but look at the Unitek head...
WAY less quench area.....
Must be making it up with a really tight squish....
:?:

[Anonymous]

I add my thanks for the pics.....very informative!!!

Cappy, I am not surprised by the pics.....it's a "PHASE IV" head!!!....larger valves etc....I would expect combustion chamber work to optimize what the larger valves can do.....they be real pretty....

....and the pics make me wonder about what we don't know.....like why are #1 and #4 intake ports smaller than #2 and #3...or it that an optical illusion? look at how much material has NOT been removed from the exhaust ports.....also interesting....

....it would be nice to have some dimensions on things in that head.....not to try to reverse engineer it; rather, to get some idea of what UNITEK has found to be good proportional relationships....

....it would also be nice to know more about what goes along with a Phase IV head to complete the package.....again, not to reverse engineer, but to understand the balance sought in the package arrangement.....

...I think JT said he got an intake to go with it.....what about the pistons.....exhaust manifold....turbo...etc...

....like in your head, Cappy, the squish area has been reduced a bit...but not eliminated in either, and can be compensated for, as you suggested....info on piston crown shape and squish height would assist analysis....

very interesting pics....thanks again to JT and Matt....

[poulson01]

....like in your head, Cappy, the squish area has been reduced a bit....
Hey :!: That wasn't nice :wink:

Nice links Stealth. I see stuff like that on the drifting forums sometimes. Nice to be well informed (if you have the time). I can't see the pics dammit! :rant: I'll have to try later.

[Captain Bondo]

Ok, so here's my logic/conclusion to htis point.

The improvement to the "next" engine work like this:

1)bigger valves and a balance of port area to valve area, make it larger overall for more flow.
2) this will lead to more chamber re-shaping to keep things unshrouded. Really, if you took my head, put oversize valves in it, and re-unshrouded it, it would be eveloving into a shape similar to the untiek chamber interestingly enough.
3)#2 has now lead to much better flow/potential ve, but it has also resulted in less quench area, and larger compustion chambers chamber which would result in slower burn, less quench/squish effect, and lower compression. So, to cure htis, flat tops are fit with a approx 40% closer squish height. This compensates for the lowered compression, compensates for the lessened quench area, and maintins the highest ve/flow possible.


YAY!!! make sense?

So:
bigger valves>bigger chambers> more flow but -squish and -CR and +burntime> flat tops pistons and tighten squish therefore +CR and +squish effect and therefore +burnrate/quality.

This would result in an engine with a net increase in breathing, as well as a net increase in detonation resistance compared to my current setup.

Starting to make my engine sound kinda crappy... ;)

[Anonymous]

Cappy, you are on the right track...but there are some issues that have not been dealt with yet....

...if you want, we can let it go at this point....(wishful thinking on your part)

...but if you want to do the job right, the other issues need to be discussed and evaluated...

...actually, I don't think that I am gonna let you off the hook just yet though.....not finished with my "pickin" at ya....besides, you are such a deserving kind of guy....

...hopefully, some others have looked at the links I put up, and have some comments/questions/analyses/conclusions/disagreements or refutations to offer...(for which I wait with 'bated breath)...

...I do want to do part 3C....some good pics to share and thinking to generate.....conflicts to agitate....revolutions to instigate...

....and I still haven't given you any grief on camshafts yet... :D :twisted:....or on ________ :shock:

[JT]

I assure you that the intake ports are all the same size. It is the camera that makes it look different. I am not responsible for the outcome if someone want to have different sized intake ports. :eek:

I listed what I paid Unitek for in a pervious post but right now all I have is the head. The intake is nothing special just a stock, I believe '97 Volvo B230FT manifold. I am getting a short block, pistons, rods, and misc things. All of this stuff has not come and I am waiting for delivery. Cannot say when it will be here but that is the plan right now. I have much assembling to do. I also have to get a new turbo and fuel management system. Iam sure that there are things that I have not even thought of that I need to do. Operation Grocery Getter is the name of this program and I set out to build an everyday driver that can put out 300+HP. I will do this with a '95 940t the last of the RWD turbos in North America. I will put a Supra 5sp tranny in it (this will work great, I did this to my 740t), and most likely do something with the rearend. I will do suspension and brake upgrades, as to what I do not know. There will also be wheel an tire upgrades. I will do a modest weight reduction on the 940t and investigate putting a 960 front end on it. So I am just in the beginning stages of a long upgrade. When it is done it should be sweet. Hope this helps someone. I know that I am going to need a lot of help to pull Operation Grocery Getter off.

Bis Später,

jtb

'living over the edge every single day!'

[Anonymous]

some catching up is in order...

...to answer the question of what would the disadvantages of "going overboard on squish areas":

...to modify the combustion chamber configuration in such a manner that the squish area is maximized at the cost of reducing the flow that was there before reconfiguration, or to reconfigure the CC in such a way to maximize the squish to the detriment of efficient flame propagation...ie make it hard for the burn to occur smoothly and as rapidly as possible.....that would be going overboard for squish....

....to create a mental image of that, consider Cappy'c CC pic posted earlier in this thread....visualize making the CC look like a figure 8 around the valves, with a little teardrop of a passage to the spark plug...(or you could think of it as a 3 leaf clover: one large leaf over the intake valve, a smaller leaf ove the exhaust valve, and a tiny leaf over the spark plug, and the 3 leaves connected by a narrow stem like passage)....yes, you'd have max squish area, esp with flat tops....and you would have crap for flow...and you would have crap for flame propagation and travel speed......

...such a CC would not be useful or desirable......squish is not the do-all or end-all....and I do agree with that....and I also contend that squish, and the other components of turbulence generation in the CC are one hell of a lot more important than most think....

iadr....yes, your comments on why the MFRs are putting so much $$ into the multivalve motors are correct and germaine....as are the problems that going multivalve have brought along to the situation....

(and I agree that to find info on hi perf mods, one has to go where the info is....and I haven't found much on volvos specifically; so I do read elsewhere.....have to....)

(and the 30 degree valve seat has some real possibilities...the improvements in low lift flow!!!....just haven't found anything yet re using 30s in turbo motors.....am concerned with heat transfer/valve cooling....that subject is on the research list)

....to improve flow, and (hopefully) the power output of an engine, the MFRs have gone to multivalve heads.....yes, the overall flow is more than with 2v CC designs, esp at the higher RPMs....

...it is good that the 4v CCs flow well at the higher RPMs....because that is where the 4v CCs make their power; they don't have it on the bottom end....they are not efficient at the bottom end of the RPM scale....

another way to put it is this: if you want to get high RPM power, you need flow....an easy way to get that flow is 4v CCs....and you do get that high RPM power with the flow from the 4v CCs....AND THAT IS THE ONLY PLACE YOU GET THE POWER WITH THE 4v CC!!!....

...you get the high end power and lose the bottom end power with 4v CCs......

need examples? show me a multivalve motor that is a torque monster below 3000 rpm....even 3500 rpm.....and I want an NA example of a torque monster multivalve motor that does it under 3000.....

....I'm waiting....

....I'm still waiting....

....Can't find one? neither can I....

My point? multivalves have their good points...AND their drawbacks....

AND GUESS WHAT!!! the MFRs are trying to do something about the lack of bottom end on the multivalves...and they are improving the bottom end power by increasing the squish areas to improve the turbulence in the CC..... :eek: :eek: :eek:

CONCLUSION to be drawn?....squish IS very very good.

...in fact, squish is so very very good that there is considerable efforts being made in the big V-8 high performance area being done by many there to improve the squish so that they can run higher CR to make more power....

....a google search for "squish quench" will yield mucho reading material on that end...

for example, an article entitled "Quench Quest" at:

www.chevyhiperformance.com/techarticles/94138/

has a lively discussion of the quest to improve the squish...along with some epiphanous pics of a SBC CC modded for squish...for all the old guys here that know the "D" CC like the backs of their hands oughta get a charge out of the pics....I did...

for those interested in what could be done to a volvo 8v head, that article shows some possibilities....

for the 16v guys, you should read up on what Endyn and other outfits are doing to the multivalve heads to improve the squish....

two links for that to get you started; the first one has the article, the second one has the pics to go with the article:

www.hondalife.com/articles/headtech.htm

www.dezoris.org/headgames/

....wanna see what toyota has come up with that is going to change everything re multivalve squish??

do a google on "tapered squish area" or "slant shaped squish"....

and there was a paper presented at COMODIA 4 in 1998 on that motor:

www.herc.musashi-tech.ac.jp/shudo/esd/Data/004/C98_P227.pdf

SUMMARY:

Squish is good....very very good.

If you read up on it, you can prove that to yourself.

If any want to discuss the subject further, like how to get more squish in our motors, say so.....and we will carry on....

...if not; that's fine.....I've said just about what I wanted to on this aspect of the issue.....from here it gets theoretical and controversial....

I am working on implementing my theories on at least one motor --the first of at least six-- for myself, a 21FT; and am working with a TB member in the mentor capacity on his B230FT project....life is good...

[SRK]

I knew this thread would be a monster. And I knew Stealthfi would add a lot to it, all excellent.

My abbreviated points, which is all I can do after re-reading most of it.

However turbulence is achieved, its purpose to to homogenize the fuel air mixture, and promote rapid flame travel. It is interesting to note that gasoline piston aircraft engines, even with dual sparkplug ignition, were limited to about 6.5 inch bore because of flame rate limitatations.

Quench is the boundary layer that is cooled to such a degree that it will not burn given the time available. Very bad for emissions.
Squish is turbulence induced by piston movement as it achieves TDC, through interaction of the piston crown and the combustion chamber. Think homogenization and flame rate. Good for those, bad for pumping losses.
Swirl is homogenization induced by port and valve design.
Tumble is swirl induced by the angle of the port to the cylinder centerline.
Fuel injection upsets the apple cart. Much of squish is needed for emissions reduction when dealing with poorly atomized fuel from carbs, and the attendant manifold separations or "drop-out" of the fuel from the air they cause. Fuel injection makes possible shapes that achieve good emissions and cylinder filling at the same time, hence the popularity of four valve designs. And of course if the roof of the chamber is full of valves, there is less room for squish areas and the quench they induce.
Time for a drink. Whew.
Good thread Kenny - got to be a record soon!

[poulson01]

Thanks Stealth, I feel much smarter! There is a couple of things though.

[quote:525ecb5ace]squish, and the other components of turbulence generation in the CC are one hell of a lot more important than most think....[/quote:525ecb5ace]

I think that most people might give swirl, tumble and other species of CC turbulance more credit than it deserves (as opposed to not enough credit). I *have* been stating the oppinion that squish areas, specifically, are very important especially in the 16v config. (Thanks for illustrating that point so bloody well better than me, by the way, Stealth).
The reason I imagine for this is time elapsed vs momentum. The squish event must be violent, brief and powerfull, as well as occuring within miliseconds of the ignition event. Blah Blah Blah. You get the idea.

Second, I wonder if you could spill a little more on what effect the shape of the drop off from the squish area might have? This is the area of the 16v CC that caught my attention as an area that could possibly be improved upon.

<edit>I have agreed to donate my damaged 16v head to science. If it is accepted, it will be disected, analysed and the findings, shared with all interested. A sacrifice, I am proud to make :mrgreen: <edit>

[poulson01]

Just checked out the pics of those Honda race heads. :o Makes me wanna run out and buy a TIG welder. Maybe if I hit the MegaMillions lottery. :roll:

[Anonymous]

to those who have contributed, and to those who have patiently waded through the posts....thank you...

....Poulson01....I am not quite sure what drop off area you are referring to....the last link on the toyo taper squish leads to a pdf file that does a pretty good job of explaining what I think you are asking about.....I had to print it out and read it about 4 times to get past the techno-engineer-who-cant-write-mumbo-jumbo....and it became clear....finally.....and there is an SAE paper on that motor that does a pretty good explanation...

what I have been trying to do with my posts has been to try to make people see that there is a lot more to it than dropping in a big cam or hoggin out the head for more flow...

....if I recall correctly, Cappy stated that his goal was to "have the highest compression pressure/octane rating ratio" he could get....

...that can be restated two ways:

to get the highest compression ratio--CR-- that he can run on the octane of fuel he uses so he can get the most power....or:


to try to extract the max BMEP from the fuel available to him via CR optimization/maximumization to make the most power.....(clear as mud, right?)

....in plain ol' american, he wants all the git-go he can git up and go with...

an admirable goal....and one that I agree with.....

...and, it is the methods used to reach that goal is where Cappy and I have some variances of opinion and Approach....

here is where it gets dicey: because what I choose as the method of achieving max BMEP is very contrary to the orthodoxy....

the orthodox method of more power involves the fixation on flow, and the brute-force approach to turbo-charging.....that is the approach used by all the MFRs and almost every aftermarketer of turbo systems....they have their reasons....primarily cost....also cuz it's easier to do it that way....less engineering involved; more compact package....and more idiot-proof...

I understand both the approach and the reasons for it....took me a while; had a lot of RAH-RAH BS about how that approach was the best and greatest and only way to do it to wade through, analyze, and evaluate....and finally to reject...

I contend that that ain't good enough....I choose to optimize all components and subsystems to work together to finesse it....brute force is for the -----(fill in the blank).....

for example:

....flow is the way to up HP....more flow, more HP....

HMMMM.....really? I thought that it was the efficient extraction of all the energy of the fuel, and applying that energy to push the piston down and turn the crank that made the power....HMMMM....

don't get me wrong....flow is good.....but flow ain't god....

also, a lot of those same people who push the flow-is-god fallacy somehow conveniently forget a minor little thing that kinda shoots their argument all to hell:

....in all their zeal to hog out the head; go big cam; huge compressor side to pump more air to get more flow yada yada, the issue of exhaust flow from the exhaust flange gasket, through the exhaust manifold, into and through the turbine housing, through the turbine wheel.....well, somehow ALL the restrictions and impediments and imbalances to that exhaust flow is magically irrelevant.....doesn't matter....doesn't affect anything yada yada.....HMMMMM....

and when queried about the issue, the answer I have almost universally received is: the turbo takes care of that.....or......that's the way it is.....or....that's the way everybody does it; what are you: some kind of nut?

....no, not a nut......just not a lemming.....

....do I know that my Approach will work? not yet....but I have some pretty good theory --and some applications--on my side....and after all: engineering is the practical application of theory to a problem; if it conforms to and utilizes the laws of physics and chemistry, it has a chance of actually working...we will see...

FOOTNOTE: this is not and has not been intended to belittle, besmirch, denigrate, ot trivialize the efforts of any here on the TB.....they are doin' it their way....cool.....I'm doin' it a different way....

[Anonymous]

after putting up my last post, I realized that I probably did offend a few people.....because it sounded like I dissed flowbenching heads....that was not my intent, nor is that my attitude...

I think that flowbenches are very useful tools....the benefits that can be derived from the use of a flowbench are many....

....further, I do believe that using a flowbench to verify what the cylinder head does do re flow, and using the flowbench to "tune" the size/shape/area/etc of the runners and ports of the head to optimize the flow is also good...

....but going for max flow is not the answer.....example:

using a flowbench to determine which cylinders are lower in flow than the others, and then correcting the deficiencies to make all cylinders flow the same is very very good....AND improving the numbers is not necessarily bad, but can be....

how so?.....the debate over swirl has been in the flowbench arena for a long time; many think that swirl takes energy that could be used to flow more air; others think swirl is good......those in the swirl-is bad group have no problem with unshrouding valves: the flow goes up--that is good.....but unshrouding the intake valve also reduces the tumble/swirl factor past the intake port...and can reduce swirl ratio and swirl speed by a factor as high as 3 (or more)...ie 3 times less swirl (ratio and speed).....

less swirl means less turbulence and lower turbulence intensity...not a helpful result in regards to maximizing the burn rate,reducing the burn time, and maximizing the extraction of the energy from the fuel to push the piston down...

to further clarify, allow me to offer an example of how I see the beneficial use of a flowbench...

use a flowbench to balance the flow of all the cylinders' runners and ports in that head--even flow capacity for each cyl....use the flowbench with a swirl meter accessory to measure swirl speed....if more flow capacity is desired, make sure that the mods made do not reduce the swirl; an increase in swirl would be a very desirable outcome.....

use the flowbench to check the flow with the intake/throttle body installed...to make sure that all cylinders still flow the same....

then use the flowbench to check the flow through the head and exhaust manifold.....to also verify that all the cylinders still flow the same....

...some are probably thinking: why so anal on swirl/squish/turbulence?

time.....time to do the job of extracting the energy from the fuel....not a whole lot of time is available to get the job done; and as rpms go up, the time available decreases.....

to illustrate:

1000 RPM crank rotates in 60 milliseconds....

2000 RPM crank rotates in 30 milliseconds

3000 RPM crank rotates in 20 milliseconds

4000 RPM crank rotates in 15 milliseconds

5000 RPM crank rotates in 12 milliseconds

6000 RPM crank rotates in 10 milliseconds


....the amount of time available to finish the compressing, squishing, igniting and burning the fuel/air mix is about 10% of the crank rotation time.....at 1000 RPM, you have about 6 milliseconds to do the job; at 6000 RPM, you have about 1 millisecond to do the job....

....I contend that optimizing the conditions in the cylinder to do the job as quickly as possible is both beneficial and absolutely necessary.....that's why I am a bit anal on swirl/squish/turbulence...

[Canuckvolvo]

(best Mr Burns voice) Excellent!

I've got a B23E block in perfect shape, a set of b23FT pistons and a nice stock 530 head available. This is going to be a daily driver, of course with lots of fun potential. Considering 90% of it's running time will NOT be in boost, it's very important that the NA factors are optimized- hence not relying upon boost for your power as Stealth said. Yes, I want good power, but I also want EFFICIENT POWER- gas just hit 80c CDN a litre here this week...

I'm really looking forward to some kind of summary/conclusion post!

[Anonymous]

I am working on my summary of the areas discussed so far....hopefully this weekend....but perhaps not until Monday or.....I want to review what has been brought up and there are a couple of more things I want to add.....

....like tumble....a bigger deal with the 16v head than the 8v head because the 8v valves aren't tipped at an angle to the deck....

....like spark plug location....the plug in the 16v is centrally located; a very nice feature....resulting in a shorter distance for the flame to travel: shorter burn time by location...that helps make up for some of the deficiencies in squish....

....and some further discourse on swirl/shroud...I am not rabidly against opening up a CC....and we will discuss some of the factors involved....

Canuckvolvo.....80 cents a liter....OUCH!...even in canadian $ that smarts....last time I was in Edmonton, I bitched about 56 cents a liter.....you have my sympathies....

[poulson01]

"Tumble" and "swirl" were the types of turbulence that I understood to have less of an impact on filling, flow and almost no impact on burn. I'm thinking that the turbulence that helps most is the type that the sqiush area creates.

The drop off area that I was talking about is the edge of the squish area where it drops off into the combustion chamber. I read the article on Toyota engines and, fascinating as it is, I think that reshaping my cylinder heads to that extent is a little beyond my capabilities (and I don't say that too often). I was looking at maybe cutting a little aluminum from the bottom of that edge to make the drop off a little higher. I don't know why I thought it might help. It just sort of made sense while I was working on the head, staring into the CC.

Also, maybe there are compromises that could be biased a lot more with a turbo than without. Maybe "the turbo takes care of that" isn't so far fetched. I lurked a mailing list, for a while, where you would see posts from old time F-1 engine builders from time to time. They built their turbo engines a lot different than their NA engines. I never go to ask about CC design but if the differences in intake design were any indication, then I wouldn't be surprised if the CCs' were very different.

[Anonymous]

Mike.....as I understand it, the swirl in the 8v, and the tumble-swirl that the 16v configuration creates, affect the homogenization of the air and fuel mostly, and help to even out the temps inside the CC--reduce or eliminate hot spots--......and so I can see your point --partly-- about not affecting the burn; I would put it this way: the swirl or tumble-swirl establishes the foundation--or lays the groundwork--for the squish to do its job......the swirl does affect the burn by getting the turbulence started, but the squish is the big INTENSIFIER of the turbulence just about at the time the plug fires.....the swirl gets the (turbulence)ball rolling; the squish kicks it into hyperdrive....

....we need both....how much of swirl or tumble-swirl and how much squish is where it can get subjective......the old debate of: if some is good, then more is better; therefore too much is just right....is not a realistic way to go at it.....and like so many choices when setting up the objectives, parameters and specs for a motor, there has to be some balance in the approach because of the compromises that have to be made......if one goes all out for squish, chances are that flow will suffer along with burn time due to obstructions--the "three leaf clover CC for an 8v" example comes to mind...

...your objectives lead your choices; which guide the direction of the compromises...

re drop off area....that's the one I thought you were talking about.....

I would agree with your assessment that to mod a 16v to be like the toyo taper squish would be a very serious undertaking....to recess the CC into the head that far would pro'ly require a new casting....if not that drastic, then some serious welding/machining and custom pistons......and still risk negative impact on cylinder head coolant flow....beyond the mod arena, and into the redesign arena.....

....but from that article, and from other sources, I see the value of the dished piston: the spreading out of that squish shockwave is wider--and therefore more influential-- when the edge of the squish area opens upwards into the head and downward into a piston dish.....a dish in the piston that conforms more to the squish area of the CC floor would maximize that; look at some of the piston dish shapes for the SBC for example....so to try to match the shapes of the squish areas of the CC floor and those on the piston crown would be beneficial...

the other thing the taper squish design enhances is the "reverse squish".....when the piston goes down and opens up the squish area, the taper speeds up the sucking of the burning mix to the outer wall.....thereby speeding up the burn which shortens the burn time....

I agree with you that there are things that have to be different in a turbo app vs a NA app......operating conditions are different..... the fact that there is pressurization on both sides of the CC changes the landscape....to the point that some things that are very important in a NA motor, are not quite as important in a turbo motor, and vice versa....

an example of this is camshaft profiles/lobe separation angles/lift/duration/event timing.....that is a whole other area of problems/conflicts/compromises because of the different environments in NA and turbo......

[iadr]

Nobody spoke up when it was mentioned Volvo's don't use true Hemi chambers. If it matters to anyone- and it might, because JohnLane's car has a number of admirers- most if not all of the V6's (I've only seen earlier ones apart) use virtually textbook hemi, opposed valve chambers. Here's a set of heads that were on Ebay:
http://www3.telus.net/public/iadr/b27v6heads

******

SRK mentioned that for purposes of reference, carbs' fuel dispersion was inferior to FI.
I would take issue with that, saying the issue is more a mixed bag. The manifold design becomes a compromise when run wet, as does the port, to a lesser degree. However, comparing injector output to the carb-produced fuel/air mixture tends to favour the carb. In a runnning engine with some decent port velocity, there is also a good chance the mixture will become better mixed (not worse) when flowed through the manifold.
I know Endyn mentions running prostock motors on FI as a development tool, and finding performance loss.

********

A reason left unmentioned for the manufacturer's tendency to go with a restricted exhaust side is for the inherent EGR function. Many of our cars -(K-jet b21ft's for sure) were engineered at a time when pollution control seemed regarded by many factory engineers as a frightening mystery. Take a look at all the cars that did not get imported in the 80's- the whole "grey market" industry that sprang up was in response to that. Having a good bit of exhaust back fill into the chambers might have been a 'lucky' way to reduce an aspect of pollution output- certainly no worse than some things that were tried, like the Ford retarded cams, and others ideas.

Maybe I'm dwelling on this, but it occurs to me that we have fewer "examined" newer tech engine packages to copy than is ideal. A lot of what we know is 80's Porsche, Ford and Chrysler thought. I'd feel a lot better about things if we had threads about the cyl pressures, turbo specs, cams specs and so on, inside Volvo S80's, SAAB Trionic 2.3's, etc.

I'd think an airflow-tuned turbo set up like you are planning, Stealthfi, would have more the effect of a N/a engine with big overlap- a pull-through of intake mix under some conditions. Bad for emissions reasons, possibly not so great for economy, though the b21ft stock wasn't great in that regard, and you stand to benefit a great deal from the engine actually being more efficient.

*********

Torquey 4V a contradiction? I disagree- I think that the torque on the low end remains about the same, even improves a bit, and stays at that established value in lb/ft per cid through higher RPM. so giving a higher Hp figure. I would agree that this has allowed manufacturers to
spec cars with somewhat underdisplacement engines, either for production economies or for MPG gains through reduced pumping losses in light use. I'm thinking of the Toyota Celica VVTL engine, here, and a few others, using 1600cc's in a mid weight car.
As far as torquey multivalves, recall that the Cummins and Mercedes truck and car Diesel use 4V/cyl. If diesel references won't sway you, Ford has just gone to 3v for the new f150's.
Honda does 4v for economy cars.

Anyway I think the argument is circular- 1/ why expect to gain low end power when switching from 8 to 16 v? Low end power is not flow restricted. A thumbnail condensation would be that low end power is BMEP, which is mechanical cylinder filling, which in turn is compression (mechanical, dynamic, or forced induction). You might be able to run more compression with a central spark plug, maybe not.
2/ if you compare an 8V tuned to give the same top end- ie an 8V with a big cam, it would have lost more bottom end. On the other hand, what if you ran 16 valves with really really short cam(s)? That's what the low end on a Honda VTEC is, and it's effective. Like I say, IMO a circular argument... but I think 4V is superior because with mild cams it gives you more area under the curve, and at the same time more rev range, allowing more torque multiplication.

**********

Stealthfi, I'm thinking you over generalized on the subject of exhaust flow being overlooked- there's always lots of talk about downpipes and exhaust. Where it can be said you are focused on to an exceptional degree is the exh valve to turbine on the exhaust side.

***********

As far as my project, it became a bit more focused after renting a Jetta TDI last weekend to cover a ton of miles quickly on short notice. It has better performance from its 90 hp@3700rpm/155lb/ft@1950rpm engine and 220 more pounds weight than I'm getting with either car I own. It's also getting 35 to 100% better fuel economy.
At the risk of being accused of comparing apples to oranges, that's the direction of set up I'm looking for, planning for. I'll use a 2632cc N/a engine, with a T cam, tight deck and modified exhaust ports, and likely eventually a custom header.
Specifics of b23E based buildup
starting points for
2630cc, 9.3:1, as cast 405 head. & then with +30 hp/ +17 lb-ft from factors detailed below
t cam 115 @ 4150rpm, 159lbft @ 2200 145/176
vx cam 130 @ 4600rpm, 159 lb ft @ 2700 160/176
a cam 129 @ 4400rpm, 166 lb ft @ 2800 159/183
K cam 146 @ 5000rpm, 168 lb ft @ 3800 176/185


After mods hp/cu varies from .903 to 1.096
& tq/liter varies from 66.9 to 70.34
* * tq hp
tight quench & thin, low friction moly rings 1 2
lighter piston and lighter longer rod (c 350g/cyl) 1 2
3 angle valve job & basic port smoothing 1 3
30 deg valve seats to help low lift flow 2 2
chamber unshrouding/reshaping & 2/3mm oversize valves 1 3
port plates on exhaust floors to radius short turns 2 3
raised compression (mid 10's) 3 4
160 deg thermostat 1 1
lightweight, premium synthetic oil, at stock pressure 1 2
Larger "16valve/B234" headpipe 1 2
big, free flow exhaust (mix of 2.25-3inch) 1 3
tight valve lash giving increased duration -1 2
cam adv 4 deg (net of any retard by deck/head milling ) 2 -1
electric fan 1 2
Totals: 17 lb/ft / 30 hp

+ lighter flywheel-gives minor, 3 lb effect. Giving sharp throttle is high vacuum cam/compression
+ vacuum advance (rather than emissions-style retard),
+ cold air intake pulling from behind headlight through cone filter

I'm a little worried about the fuel injection's ability to be adapted for such a change, and a little worried about light throttle pumping losses with the high cylinders pressures. It may be like a 2-stroke 'on the pipe', and work perfectly, or it might teach me something... :( I'm also worried I'm duplicating the old BMW 325e engine, which made only 121hp@4250 & 170lbft@3250 with +70cc's (it wasn't 2.5 liters). They did have 9.0:1 compression where I am cc'ing with 10.75:1 in mind. Thoughts?

[poulson01]

Stealth. We're on the same page, I think. The only thing I think you left out was at the bottom of your post. You left out CC design, port design and manifold design. Cams and all that other stuff is old school. There are reams of info (100 years worth) on those subjects. You could go nuts trying to read it all. What I'm trying to figure out is port and CC layout. Advanced fluid dynamics with a little centrifugal fan to really complicate things.

iadr. I have to take issue with a couple of points. Obviously, we're not in agreement about the 16V torque discussion. Again, I base all my arguments in this area on seat of the pants data. The 16V Volvos that I have driven have felt boggy even though the final drive ratio is shorter than the NA 8V equivalent. It isn't compression ratio because the 16V has the advantage, yet it has less snap then the 8V. It may be the engine management but I find that unlikely. We're in agreement that it is probably not cylinder filling or flow. It must be something else. Also, Im glad you enjoyed your rented TDI. When I worked for VW, that was the engine that impressed me most. Too bad the government put the kabash on that little diesel. I'm sure there'd be many more out there, otherwise. I have to point out that DI diesels *are* "apples and oranges" when compared to gas engines, even if the configuration is similar. My friend Jerry was working on deisel engine fuel droplet combustion when I discussed CC design with him. Direct injection of fuel into the CC under X,000psi creates the same kind of turbulance and fast burn as a well engineered squish area. This is probably where the new diesels get their rip snort'n torque from, as well as their impressive top end.

[Captain Bondo]

I've been just observing this as there's just too much to type.
For one thing, I'm fialing to see why stealth's theory is much different than my. I have not applied all of that to my project, but that is more due to budget and other compromises. The reason I started this was to get some more discussion happening on some fcators that i feel are important, but that I possibly did not implemet well. This is for the purpose of implementing these things more in future evolutions of the car.

I agree tumble and such other forms of turbulence are pretty minor in overall effect compared to the actual squish turbulence. My feeling is that low-intensity turbulence might help keep fuel form literally pooling in areas before the squish event occurs, but it's the squish that really homogernizes the existing aerosol fuel mix.

I'm confused by the 100hp at 4000rpm vs 100hp at 8000rpm... which is more energy? maybe this is a trick question, that or I'm missing something. As I know it, power is energy per unit time, ie if you convert it to watts, that is Joules/second, where a joule is exerting 1 Newton meter of force over one meter I think....either way, 74,600 joules per second is 74,600 joules per second regardless of rpm. Same hp at a higher rpm suggests less torque production since power is the multiple of torque and rpm.

[Anonymous]

iadr....first, a thank you for the time you put into it....I appreciate that....

I never considered the PRV v-6 to be a volvo motor....no offence intended....

I am glad of your awareness of the residual spent gases effect of the high EBR approach.....few are....and I had not brought it up in this discussion because it is more related to camshaft and exhaust EBR areas of discourse....but, yeah, the residuals are why the turbos did not have to have EGR valves....they finessed it: used a problem to resolve a different one.....

I agree that more attention to what is currently being done re turbos and multivalves regardless of the source MFR can be very helpful to our efforts to improve our own...

re my engine program parameters....I'll be doing camshaft specs somewhat differently then you might think.....big overlap is not in the picture....

....not sure what poor mpg is to you; but I get 24-26.5 mpg on my B21FTi now....emissions are not important to me; even tho mine does pass the annual test easily.....I want efficiency.....to waste fuel is inefficient.....fuel efficiency is one of my concerns, but it is a side benefit of optimizing the burn etc...

we will continue to see 16v bottom end torque deficiencies differently.....diesel multivalves are not the same as gas multivalves.....

I disagree as to it being a circular argument:

....the point I was trying to make was that 'IF' I were wanting to get some high rpm power, I could do it with an 8v; I would not "have" to go 16v to do that......with the unstated understanding that to get those results with an 8v, there would be some loss on the bottom end....

....and I was trying to say that when multivalves came out, they were done to up the mid and high end.....and that recently, the MFRs were working on improving the bottom end power of their multivalves.....squish enhancement being one of the methods....

I think that perhaps my lack of enthousiasm for the 16v is being interpreted as an attack on it....I am not attacking 16v.....I do not need it to do what I do, and will be doing.....to those who like the 16v, I say: go for it......not my cup of tea; but if it's yours, cool.....hopefully, some of the things I have mentioned are helpful to your quest......I am not trying to dissuade any 16v enthusiasts....

on exhaust flow, I was doing more of a disregard thing....the subject of exhaust post-turbine has been just about beaten to death on the board.....the issues of EBR pre-turbine has received scant attention; on that I am focusing considerable attention...

yeah, those little TDIs do run....interesting how bottom end power can be so fun....

your motor plans sound good; would like to hear more re the objectives/goals/use aspects.....it would help to evaluate your choices.....with the intent to offer suggestions to help, not to dis'....this sounds like the basis for a very good topic for you to post.....maxxing a NA has not been deeply delved into here, in some respects IMO...

....am I correct to assume your goal of optimizing low-midrange power?......in NA, the adage of "no replacement for displacement" is hard to defy.......

Poulson01......now Mike, I was just giving "a" example....what you mention is on the complete list, which would pro'ly be 2 or more pages......

....."advanced fluid dynamics and a little centrifugal fan"?...HMMMM....if I follow your drift, I would have to suggest: why not try some helical flow inducers instead of the fan?....HMMM?

Cappy....you are right: our goals are the same--essentially--.....where you and I differ is in which steps first taken, and in some of the priorities.....or maybe better described as different viewpoint as to route there.....

I have been trying--pro'ly VERY 'trying'-- to give imput for the next stage and stages in your project......

we both seek the highest CR/OR ratio: max BMEP.....just little divergences in what you and I see as how to get that.....

.....so, to make you see it my way, haha, I am wearing your resistance down with my eloquent, lucid and cogent arguments......(ok, you can barf now).....heehee....

ASAP, I will wrap up my side of the discussion and post it.....I felt compelled to reply to iadr's post....I appreciate his efforts and viewpoint, and wanted to say so....plus I wanted to razz the Terrible Ted....

[poulson01]

[quote="stealthfti"].."advanced fluid dynamics and a little centrifugal fan"?...HMMMM....if I follow your drift, I would have to suggest: why not try some helical flow inducers instead of the fan?....HMMM?[quote]

:gulp: See! I told you we were on the same page!


<edit>Just in case, I thought I would specify that the "fan" I'm reffering to is of the Garrett T3 variety. Again, not trying to insult anyones intelligence<edit>

[Anonymous]

...how's this for an excuse: I understood, but it was a misunderstanding.....pretty lame...

...actually, Mike, I was thinking of a different tack when you said AFD and a little C fan....now I see the light re what you were and are referring to....

If I am now following you correctly, you are trying to figure out what to do to the port and CC for a turbo 16v....right?

...if that is the case, then you should look at some of the COMODIA papers on the port flow for multivalves.....some will be about diesel motors, but the probs those multivalves have are along the same lines as what you are trying to deal with for your app...trying to improve the turbulence....

....where I got off track was when I saw "advanced fluid dynamics"....that got me thinking mods to the intake manifold or runner/port to induce a helical flow....that was the subject of one of the papers at COMODIA--their drift was towards a different method than I was thinking....

....the upshot of the paper was that the flow from the 2 intake valves run into each other in the CC and create certain "problems"...and a possible solution mentioned was to either shroud the valves or induce opposite rotation of the airflow past the valve heads....that made me think some....

....modifying the shape of the runner where it splits to the 2 valves to generate a opposite swirl is do-able.....be kinda hard to quantify the results, but it could be done....

...I started thinking of using some flow inducers to generate the opposite swirls, but as helical flows......in some ways that would be just as hard as trying to alter the shapes of the runner(s), but in other ways easier.....

one thing for sure....a flowbench with a swirl/tumble meter would be necessary to make it happen....unless you have access to some serious CFD software/hardware....

....all this stuff I just mentioned is on the far fetched side of things, I know....

something closer to easily do-able would be to build up the squish area on the head between the 2 intake valves to create some shroud effect to direct the flow to change the flow collision....and a side efffect could be better squish...(the piston crown might need some work to assist in that)

whatcha think?

[poulson01]

Here's the story. About 4 years ago, I bought a B234 from a friend for $50. The valves were all bent and the head was bang'd up. We had figured out, a long time ago, that the 16V head would bolt right on the other red blocks and all you had to do was figure out a cam drive. (I know it involves, clearly, a little more than that). I spent a lot of time staring at it, did a little welding and grinding and started to wonder if it would be worth it to reshape the CC. The B234 CC couldn't be more simple. Not a work of art by any stretch. Those beautifull Honda cylinder heads really do make me want to go out and buy an old TIG welder.

All of what you are saying is logical. I visualize your ideas of using the fluids momentum/tendancy to swirl, to help fill, prevent reversion, aid in atomization, etc. I can see it happening. The only thing I am not able to visualize is the effect a turbo, whipping the fluid at 100,xxxrpm, has on the way the fluid slips down the intake, into the ports and finally, what effect forced induction has on the dynamics of the CC. I've heard that instead of a rough finish inside the intake ports (like in a NA motor), a mirror finish is better (ONLY FOR TURBOS). How come? Is it because the fluid is lubricated by micro vortices, like little ball bearings along the walls of the port? To generate these vortices in a NA intake, you would need that rough finish. What if you have a turbo generating these micro vortices for you? Would you still benefit from the rough finish or would a mirror finish facilitate better flow?
What about after the cylinder has filled and the valves are all closed? The higher pressure of the fluid in a boosted setup must have some effect on the dynamics of the burn. The viscosity of the fluid is changed with higher pressure. There must be significant adiabatic heating with raised boost as the piston compresses further, the compressed intake charge. All these things are hard to visualize. Not like a plume of writhing cigarrete smoke in a still room but more like the different pigments in the paint in a 1gal tin, being agitated in one of those things at Home Depot. Can't quite get my brain around it.

[Boris740]

Mike,

I agonized over this turbulence, micro vortices, laminar flow etc and concluded that the scope of my ignorance will always outpace the bits of information that I pick up along the way. Note that the bits of information do not necessarily equal to scientific fact. Keeps me up at nights. Rough versus smooth surface. Golf balls are dimpled and some soccer balls are coming out that way to. Note that both of them usually spin. Airplanes do not spin if they can avoid it and have as smooth as surface as can be gotten. I recently ported a 530 head that will be getting a V15 cam. The exhaust ports were highly polished but not enlarged much except to better match the manifold. My theory is that enlarging the exhaust would allow a larger surface area of the ports to absorb more exhaust heat. This is a waste of energy better used pushing a turbo.

The intakes were made smooth and matched to a manifold. The matching was accomplished by making a thick intake gasket, almost 1/2" out of phenolic. This allowed me to bolt the gasket to the head and match one half to the head, than take it of and match the other half to the manifold. A side benefit is that thicker gasket keeps the heat out of the intake manifold when you are sitting at the light.

The intake manifold is polished smooth but the head intakes are only contoured to remove sharp angles and transitions. They are bead blasted. Slightly roughened surface is not to promote any micro vortices (it might) but to help with fuel evaporation. Since the Volvo is bank injection system, meaning the there is a plenty of time when the injectors are spraying and the intake valves are closed. This causes the fuel to coat the intake walls and valve so slightly rough surface promotes the fuel evaporation.

To promote the swirl I ported a portion of the chamber wall in a shape resembling a letter C. This semi circular channel starts at the head center line - intake valve wall and heads toward the spark plug. The idea is to create a path of lower resistance for the AF mix as it enters the head give it a counterclockwise spin. The head will be installed this spring.

[poulson01]

Hey Boris. I remember our discussions when you were researching for your port/polish job. Sounds like you've done a lot of work since then. You did a custom throttle body too, right?

How did you work the combustion chambers?

[Boris740]

Hey Boris. I remember our discussions when you were researching for your port/polish job. Sounds like you've done a lot of work since then. You did a custom throttle body too, right?

How did you work the combustion chambers?


How did I work it? You mean tools and methods? I used various sizes of flap wheels in a die grinder, electric drill for ports and Dremmel tool for finishing work. I also ground down the tops of two valves to serve as protective covers when working around the combustion chamber walls. I also polished the intake and the exhaust valves to minimize the crud buildup. I wrapped aluminum tape around the valve stem and put in the electric drill. With the drill spinning I applied the die grinder with a flap wheel to the valve and cleaned it. Next I switched to various grades of sand paper. Got carried away and went all the way to 1600 and than to crocus cloth. By the end you could see your self in them. Never touched the seat mating area. Guys at the head shop where they did a three angle valve grind were impressed. I will be impressed when I dyno the beast. As far as throttle body mod goes I have the write up. It might be to tedious to post here. I posted it once on old turbobricks and it disappeared. The head goes on in the spring when I get some decent summer tires and by that time the MVP clutch will be broken in.

[Anonymous]

Mike, I understand your position re wondering just what effect the turbo actually has on the flow dynamics.....me too...

this is how I see it.....

whether NA or turbo, it is pressurized.....in a NA, we have atmospheric p pushing on the air/fuel mix through the intake/runner/port.....with a turbo, we just raise the pressure....whether or not there is any measurable or discernible viscosity change, I have not read or heard anything anywhere to either say there is or isn't....the closest that anything I have read that might even be close to a discussion of viscosity is re the density of the air charge under boost.....nothing to indicate any change in the behavior of the air due to its increased density; except maybe burn faster....still a gas; just compressed more.....

maybe there is something to your notion of viscosity.....but I have not read or heard anything that even hints at that.....

back to the dynamics.....

....I have found it a bit strange, but that could just be me, that in everything I have read, or to those I have talked to, there has never been anything about flow testing a head to duplicate boost....[maybe Ian or Cappy or Matt Dupuis or Rhys or someone else here may have knowledge of someone actually flowing a head under pressure to duplicate boost]...

...which has caused me to think that either this is some big error and oversight on the part of all these experts and specialists--doubtful-- or it is not that important.....OR maybe it has some effect, but not enough to warrant the extra effort to do a boost pressure flow simulation on the flowbench....maybe that's where the adage of: if it works for NA, it'll work better in boost (rough paraphrase).....

the only way that I know how to answer that question, and to resolve the issue of any dynamics changes due to boost is to buy my own flowbench setup and try it.....have given it some serious thought.....and I will be buying a 'bench next year.....not so I can become some kind of cyl head guru or anything....no...I just want to be able to check things out for myself....and it actually will be cheaper to get my own 'bench....esp after I started making a list of things I would like to know and quantify....

re what the boost does to the burn....if I understand correctly, the pressure increase has a positve effect (speeds it up) on burn rate...which is helpful....

re the polished or rough intake runner surface debate.....have heard both sides for years.....I am in the boundary layer camp....ie I go for the textured surface.....NA or turbo....have not read or heard anything that convinces me that polished is better....

I do not know what else I might add to help you find the answer, except to say that maybe if you look at it like this:

.....what ever you have re flow or swirl or tumble or squish in NA, whether "good" or "bad", you will have more of it under boost: more good or more bad....

does that help ya?

Boris....I would love to see some pics of your cylinder head....as well as hear how it does on the dyno.....

[swede242]

I have to ask this now that the texture of the intake runners has been mentioned....I was told by (I believe Mike A.) a couple years back that because of the position of the injectors in relationship to the intake runners, polished WAS better....that if the injectors were positioned directly INTO the runners, then rough would be better for the "mix".

:e-shrug:

???!!!

[Mike]

swede242:

> texture of the intake runners has been mentioned....I was told by (I believe Mike A.) a couple years back that because of the position of the injectors in relationship to the intake runners, polished WAS better....that if the injectors were positioned directly INTO the runners, then rough would be better for the "mix".

If I'am the source I hope I tried to suggest that the intake/induction channel surface format on injected engines are not as important as on carburated engines.

And this might be taken somewhat further via adding that on NA-carburated engines it is even more important than on carburated boost-engines.

I suggest the issue might be the very finely & homogenusly defined spray/aerosol vs the often very and uneven LARGE droplets on a carburated engine compared to a mirrofinish surface (with a small surface) vs the rough surface (i.e. with larger surface)

Best regards

Mike

M.Aaro@mail.bip.net

Luleå (northern part of Sweden)

(New file version via e-mail: Gr11/Head & Gr24/Engine-kit & Theory [all Zip + PDF)

[Anonymous]

Summary:

To achieve the stated goal of "the highest compression ratio/octane rating ratio possible" we have explored the following:

...in order to maximize the extraction of the energy of the fuel being burned, in order to generate and maximize the force applied against the piston to push it down on the power stroke, we need:

...to burn the fuel as rapidly as possible (burn rate), in as short a period of time as possible (burn time), to complete the burn and achieve maximum pressure on the piston at the optimum point of rotation--about 18-20 degrees ATDC--to make the most power...

...and we need this rapid burn rate and short burn time to occur in a controlled manner...in such a way as to eliminate the possibility of the occurrence of detonation...which is an uncontrolled, super-rapid burn--aka explosion-- resulting in temperature and pressure spikes which can cause severe engine damage...

To this end, several factors come into play.....

...we know that turbulence of the air/fuel mix in the CC results in turbulence of the flame front, which speeds up the burn rate...

...we know that this turbulence starts as the incoming air/fuel mix passes the intake valve(s) on its way into the cylinder...

...we know that this flow is known as swirl or tumble or swirl/tumble...

...we know that the configuration of the valve(s) and the shape of the combustion chamber affect the direction of, the amount of and the speed of this swirl or tumble...

...we know that this swirl can become an established flow/movement as the piston goes down towards BDC on the intake stroke; and that this flow/movement can achieve velocities and characteristics similar to what is known as solid body rotation...

...we know that this swirl or swirl/tumble creates turbulence and promotes the atomization of the fuel particles and promotes the homogenation of the air/fuel mix; which increases the quality --or completeness--of the burn...

...we know that as the piston rises towards TDC on the compression stroke, this swirl/tumble/turbulence is increased, further aiding the homogenation of the air/fuel mix...

...we know that as the piston reaches TDC, the turbulence of the air/fuel mix, and of the turbulent flame front, can be intensified by squish...an airflow shockwave resulting from the near approach of the piston crown and the cylinder head--these near approach areas being known as squish areas--...

...we know that the turbulence intensity increases generated by the squish shockwave enhances the flame front movement, increasing the rate of the burn, and shortening the time needed to complete the burn...

...we know that squish areas and squish action reduce or eliminate most if not all of the conditions needed to induce detonation...[other factors like octane rating of the fuel being adequate]...

Observation:

Squish IS very very good!!

Suggestions:

How to improve squish

Since squish action is the result of the near approach--think of it as an almost collision-- of the piston to the cylinder head, there are ways to optimize squish, areas and action...

...we have discussed, and seen examples of, cylinder head combustion chambers shaped and configured to optimize squish area.....whipping out the old TIG welder and going to town is an option and a serious decision to be considered carefully....

...we know that the boundary layer effect--aka the law of the wall-- comes into play if we can make the near approach (the squish clearance) about .040 inch....

Sounds easy enough, right?

Not quite. There are physical factors that can affect and influence our efforts at optimizing squish clearance...

In general, published recommendations on squish clearance have settled on the .040 inch specification as the desirable clearance; and these recommendations come with warnings and qualifications....

...these general qualifications are:

a) if the engine is going to be run above 6500 rpm, more squish clearance will be needed to accomodate connecting rod stretch...

b) if the piston has a lot of clearance in the bore, and can "rock" back and forth, then more clearance will be needed to accomodate the piston rocking upwards....

We can get into some of the specific considerations re our redblocks if the desire is expressed....

And there are some other things I would like to add, but it is late, and I've had a long week....

[Tuff240]

I have been away from the tb board for a little while and was ignoring this post because I figured it was way above my head and I knew it would take a long time for me to read. I have learned more in the last 4 hours about the top end of a motor than the entire 30 years of my life. And I haven't even read the articles stealthfti linked yet! I'll read this entire post a couple more times to make sure I'm understanding it before I go on to those articles. By the last page of the post I was actually starting to understand it! Of course if you figure in that I never even finished high school, I think I'm doing pretty good! LOL

I would like to send out a big thank you to everyone that has posted thus far, it has helped me TREMENDOUSLY.

Patrick D.

PS, I should have hired a professional. I now have melted candle wax stuck in my carpet....LOL.

[Anonymous]

re the physical factors affecting how tight the squish clearance can be.....

...besides the rpm/con rod stretch factor, and the piston "rock" factor, there are a few other factors that come into play:

...as the piston absorbs heat, the alloy expands....the piston grows wider--getting tighter in the bore--and it also grows taller....and it is this height increase that can affect how close we can set the squish height....

...as mentioned before, good squish areas help the piston to run cooler, by helping even out the heat by the squish shockwave airflow, and by proximity heat transfer--the head material absorbs heat from the piston surfaces near it in the squish areas...

interesting, yes?

...we get all the power-making enhancement effects from good squish, and we get an extra goodie on the side....literally....

...review the pic of Cappy's CC...and look at where the squish area is....around the circumference of the piston....except of course where Cappy removed more material at the sides of the valves: at the 3 o'clock and 9 o'clock positions...[couldn't pass the chance to razz ya Cappy]....

....what this shows is that the portions of the piston crown outer edge that are part of the squish area will run cooler....which is helpful in minimizing piston growth, both sideways and height-wise...[and we haven't even mentioned the added benefit of keeping the ring land areas of the piston cooler and more stable]...

...back to the lack of circumferential squish area on the outside of the valves....GUESS WHAT!!....that area is directly above the wrist pin bores and the wrist pin itself....

...so what that means is that the piston area that gets warm anyway--the pin bores--also have to endure a higher heat load because there is less squish area above them....

{does that answer the question you had when you measured a piston and found that it is only "round" where the rings are located, and oval below that?....that is because the piston expands as it gets hot, and it gets hotter there at the pin bore areas, so if they don't want to have the pistons grow so much that they seize in the bore, they machine the piston oblong....kinda neat, right?}

now if you are thinking that that result is not good....you are correct...(and you get a gold star)...but we will come back to this in a moment....

....remember the piston "rock" factor?....if the piston can run cooler, we can run tighter piston-to-cylinder wall clearances, thereby reducing the rockin'.....AND which also helps keep the rings stable so they can seal better...

Which brings us to the validity and value of having piston cooling....esp if done via oil spray:

...with oil spray, a stream of oil is aimed at the bottom of the piston...and it usually hits the pin bore area of the piston....very good, right....but unfortunately, volvo only has one squirter per cyl, so only one of the pin bore areas gets a cooling spray.....

piston oiling is very very good to have...and there are ways to add the capability to an older block....but that is the subject for another article/post/discussion...

there is one more factor affecting squish clearance.....and that will have to wait until another day...

[poulson01]

I had the same thoughts on piston cooling. I have a Miata engine that has nice little banjo bolt squirters. I have considdered drilling into the main oil galley and tapping the holes.

[Anonymous]

the other factor to be mentioned that can affect squish clearances determination is primarily for manual transmission equipped engines...

...the con rods in such an app face further stretch loading due to the fact that the engine can experience high rpm closed throttle conditions...

for example: winding out in second gear to 6000 rpm, then taking your foot off the gas....the engine is still revving high, but there is very little air/fuel mix coming into the cylinder to resist and slow the piston down on the compression stroke; similar results occurring on the exhaust stroke...

...with the greatly reduced amount of air/fuel mix quantity, and the resulting reduced amount of exhaust gases to be pumped out, the piston has little opposing it's rush towards the cylinder head.....and so there is more stress placed on the con rod as it stops the piston at TDC....

*****************

All these factors have to be taken into account when calculating how much, if any, material has to be removed from the engine block deck in order to arrive at the desired squish clearance...

******************

I have some observations that I would like to post, to kind of tie it all together; and will do so ASAP.

to Patrick D....am glad it has been helpful....you're welcome.

[luke242ti]

I would have to agree with Pat D.
I have learned so much from this post, enough that when I eventually get to building up the B23FT that I have, much more thought will go into it
than just a "port and polish". I admit I must plead ignorance on 99% of this till Kenny brought this up, and the topic has been discussed in depth. :e-shrug:
I hope to learn more! Kudos to everyone! :D
Thank you all!

The entire combustion relationship with squish, swirl, turbulence
and all that is very interesting.

this might not apply here, but on the debate of 8v vs 16v and their
port velocities.

Someone mentioned a dual throttle body application. I have wrenched on and driven a car that is equipped with this. bmw 318is. 1.8L 16V 4cylinder with a small throttle body that opens first, and progressively opens a bigger throttle body. it seems to work quite well.

Would this dual throttle body operation help low RPM intake port velocity at all? :?:

thanks
take care

Luke

[Anonymous]

This has been an interesting excursion.....many related and intertwined topics have been mentioned....and frankly, most of those are worthy and deserving of their own excursions/explorations/discussions....personally, I would describe it as essential worthiness...

I got involved with this topic here because research/experience/analysis/and sometimes less than gratifying results had made me very aware that what goes on inside the CC is really the key to making the most power....and since I like power AND efficiency, getting the most bang from each bang made sense...

...I would rather have 5000 high quality, highly efficient BIG BANGS that kick a$$ per minute than 5000 wimpy, wasteful, inefficient little bangs per minute....and if I decide that I want to take it to 7000: those BIG BANGS will kick some SERIOUS butt!!!

...I realized that just my saying it would get nowhere: I am not known personally by just about everyone here; and skepticism is a virtue that I practice and respect....

So, if I could organize what I do know, and gather and present information that could not easily be dismissed as one crackpot's demented ranting, I figured that I had a chance of piquing curiosity and interest....and get people thinking about things they may not have thought about before, or may have not thought about in the way I wanted them to look at it....AND that they really needed to be aware of....

Why go through 50 pages of PITA typing? because the subject IS important; and the benefits that can be realized are worth the effort...

Cappy stated the goal correctly: the highest CR to octane rating ratio possible.....that is, to get the most bang out of each bang, considering the quality of the fuel available to use...

....improving flow is part of the equation....but it is how efficiently the flow is used to help pull every last ounce of power out of the fuel when it is burned in the CC: THAT is the key to max power....

Bottom line: Squish done right is artificial octane....[and it is "FREE" octane].....and whether NA or boosted, 8v or 16v, daily driver or redline screamer, extra octane is always good to have......what would you do if there was a way to raise your fuel octane rating 5 points for "free"?

What COULD you do with 5 point higher octane fuel?

...think about it...

...now, think about it some more....

[I am thinking that I can run a higher CR AND higher boost in my motor....hmmm.....definitely possible....it's being done in areas of racing.....HMMMM....]

...still thinking??...

...now that you've been thinking some, I can say that "squish is very very good".....and you "know" it ain't just me saying so.....

keep on thinking....keep on reading...keep on analyzing....

[Captain Bondo]

Kick Ass.
Exactly the kind of thoughts I was having that inspired me to start the topic. awesome stuff.

[Volvo78GT]

Interesting head pictures:

http://vclassics.com/pics/mp_head.jpg
source: http://vclassics.com/mppe1.html

Specs:
1974 carburetor B20F casting (not U.S. export model), modified by Unitek&ST. This is their "Phase 4" head with a few extras.
Intake valves: 46mm original R-Sport
Exhaust valves: 38.5mm modern
Si-Bronze valve guides
Double-wound valve springs
Special head gasket from OJ Rallye, compression ratio will be 11:1 after final machining.


Pics I've gotten from another guy who got a unitek 530 (?) head:
http://www.pbase.com/kalazdar/unitek_phase_4_530

Just dropping in those pics.

Keep this up! Great thread!

[Captain Bondo]

Thanks for the pics matt!

[Volvo78GT]

Gutted 16V pics at work (4 valves and cover missing... but otherwise complete! its for sale!)

http://www.pbase.com/kalazdar/16v

Check that out.

[Captain Bondo]

Just a followup,
Gasket Works.. www.headgasket.com oddly enough...
will do one off copper headgaskets for about 75 bucks. Yee haw.
Definitely on the to do list.

[Anonymous]

Since my last post here, issues related to the main focus of this topic were brought up in another topic [dbarton's 240Ti boost retard topic]...from that discussion, I realized that there are some questions that were left unanswered here....

I decided to incorporate some of that material here: because it should be here.....and to commence the effort to answer those questions left unanswered or unclear....and perhaps some not yet asked...

Appendix A: some complicating factors...some possible solutions...part 1

What is a good squish clearance?

...from all the published sources I have found, the clearance of .040 inches between the piston crown and cylinder head squish areas is the most accepted/recommended specification....[and that is taking the limiting factors --like rpm redline-- that were mentioned in a prior post, into account...

.040 inches is a good place to start....from a couple of unorthodox sources, I have been persuaded that .035in to .039in squish clearance is the clearance to shoot for for street; again with the limiting factors being considered...

Squish clearance, or "deck height" as it is called by most machinists, is "adjusted" by machining away material from the top deck of the block, not by removing material from the deck surface of the cylinder head...

...and how much metal to remove is a decision [based on calculations] made at engine build time....it is a procedure done on a bare block, not one performed with pistons, rods, and crankshaft installed...

some complicating factors are:

....boring the cylinder oversize and/or increasing the stroke--"stroking" the motor--...either procedure raises the static compression ratio....

[raising the CR is not actually a bad thing.....being able to run with a higher CR is one of the goals we seek to accomplish, and optimizing squish area/action helps us do that...BUT, if the boring and/or stroking raises the static CR to a ratio that is too high for the fuel that will be used, then that CR increase has to be reduced somehow]

...how the increased CR is reduced is where the complicating factor lies:

...one method is to remove material from the combustion chamber: making it larger; reducing the CR...[and this enlarging of the CC in the head is also done sometimes when trying to improve flow/unshroud valves]

that method does work: the static CR is reduced.....but two side effects result that may not be helpful:

...the larger head CC makes for a longer burn time: the flame front has farther to go...

...the removal of material usually reduces the squish area at the deck of the head...

A means to avoid those two side effects might be to use a dished piston instead of a flat top piston.....or to use a piston with a deeper dish than previously used....

...a variation on that theme would be using a piston with what is called a "mirror dish"....the dish in the piston crown matches up with the shape of the head CC's floor...

Using dished pistons allow the static CR to be reduced, without increasing the burn time....the CC is larger volume wise, but the farthest points from the spark plug have not been increased.... and research has shown that dished pistons can enhance swirl pattern characteristics and velocities....a couple of "good" effects, in my opinion...

Re mirror dish pistons....[in context of use in the SOHC 8v redblock]

...although they are an expensive option, mirror dish pistons offer two nice features:

1)...the mirror dish can reduce or eliminate the possibility of valve interference....a nice feature to have with a high lift cam...

2)...the edge of the mirror dish, and its counterpart on the head deck, enhance the squish wave propagation....the wave has mirror shelf edges to flow over and out from....

...to be continued...

[Captain Bondo]

Ok, I'm bringing this monstrosity back from the dead. It ain't over.

Look at this pic:

http://www.pbase.com/image/12308244

This is fomr our beloved Matt's old Pbase. You mention stealth that unshrouding may lead to longer burn times and less squish area(well, really, that is the premise of the whole thread). But in looking at that pic, I suspect the the burn time has not increased substantially- because the combustion chamber wall opposite the sparkplug is relatively uuntouched- a lot of the drastic material removal is from parts near the plug. I think the overall area has decreased, but this is where the tigher deck height comes into play, a tighter squish increases the fuunnction of the availible squish area. So, you sort-of get the best of both words-
unshrouded valves, and a good burn. Seem like a reasonable(ish) compromise?

I imagine measing this be using a straightedge on the block deck and a feeler gauge between that and the pistons while moving the piston through tdc. Is this an acceptable method?
My hope is to determine the existing piston to deck height of my current block and then order a copper gasket of thickness to suit. Standard thicknesses are:

022,.032,.040,.043,.048, .054,.063,.070, .086, .093, and .125 inches.


I doubt they will be far enough below deck to get away with a 0.032....

Hopefully 0.040 won't be too thick... these things seem to have random deck heights though as was mentioned earlier.

Modifiying the chambers of a 405 in a similar fashion to that shown above, in combination with the NA flat-top pistons and tight squish should give

1)a good CR
2)a good burn
3)good flow.

Does this seem realistic?


Just trying to nail down some conclusions.

[Anonymous]

Cappy...without re-reading the whole thread, I will say this:

You are convinced that working over a CC, like in the pic you linked to, is necessary. Okay. For discussion, we'll make that a given.

In that pic, some of the squish shelf surface has been removed around the CC. Also ok: for unshrouding, and better flow...I understand that.

I agree that setting up a tighter squish can compensate for the removed material: better squish action as the piston top comes that little bit closer to the cylinder head deck. Using flat-tops will further enhance the squish effect. Therefore, I agree with your conclusion: tighter squish can compensate for the removed material ; burn rate should not suffer...[I do think the burn rate will improve if you can get the squish under .040in]

The measuring method you describe should work fine. I will assume that you are going to do this buildup with a B21 or B23, right? The M rods should be able to handle the rev's and not stretch too much; meaning that if you keep it under 6000 you should be able to get away with a .032 squish [assuming the pistons are flush with the deck]. Every .001in that the piston is below the deck will widen the squish.

Since we let this topic take a rest in March, further research on my part leads me to think that having a squish clearance of .035in or tighter is better. I'm about to do a 91 B230FT; and will set the squish to .032in. It is for a DD; using B230ET pistons [shallower dish than FT pistons]. I was planning on reporting the results

With an M-rodded B21 or B23, I think that you could do a squish of .035in and still rev to 6500 safely...7000 might be pushing your luck. The rpm redline you decide upon is the fulcrum to balance what squish clearance you decide to go with. If your pistons are below the deck .003 or .004, that .032 HG sure looks good.

If you can see your way clear to go with the .032 HG, I would suggest installing an RPM limiter...just for insurance. I can resist anything except temptation; and suspect you have the same virtue.

[Canuckvolvo]

Holylooya, it is risen again! Atta bring it back Cap'n.

Matt and I have been going through this very debate the last few days as we've been assembling my block and prepping the head. i think I'm going to shoot for 0.035-0.040" deck height, but the debate is where to remove material from the head to maintain a "reasonable" CR?
Matt gets all giddy and his voice goes all squeaky when he starts talking about combustion chamber modification, visualizing flow in and out of valves and what not, but I hesitate to go crazy on my project. Next summer, if all of us Calgary brickers have some time, we may collectively try some REALLY silly stuff on a donor motor...oops, keep the cat in the bag athal...

I think due to my modest power goals (<250hp) I should focus on burn characteristics more than flow. I'll remove material from the head without taking away too much quench pad- we've marked the quench areas from the dished pistons on the head so theres a we bit 'o material to be taken out directly across from the plug, and we'll blend it in as best we can around the exhaust valve. This shouldn't increase burn time as the longest path is the far side of the intake valve.

I'll try and take some more pics as we go, hopefully the block will get decked next week.

Maybe this thread should get a sticky? I know I've reffered people to it more than once.

[Anonymous]

Canuk...I would suggest that if you get the squish good and tight, the static CR is not as critical a factor as you might think...dynamic CR will have more impact...[and DCR you can change via camshaft...a la intake valve closing timing]

...it sounds like you are trying to minimize removing material from the squish shelf in the head CCs...very good...that effort, along with the dished pistons, combined with either sufficient machining of the block deck or HG thickness choice to get tight squish, will reduce the negative effects of a higher than 'normal' static CR...

...and if I may go further, I would suggest that you would yield greater benefits from reducing flow restrictions after the exhaust port...as opposed to spending a lot of time on the cylinder head internals...by that I refer to installing the late turbo exhaust manifold, opened up for better flow to the turbine; and to a larger diameter exhaust...[and better yet, a 4 tube equal length pulse header feeding a twin scroll turbine, then into a 3in or 4in DP; but I digress...sorry]

and I know that these suggestions are the basis for some of the controversy and debate here...

[Anonymous]

I'm about to build the "last 16V race motor". Can anyone tell me the compressed stock head gasket thickness. Seems to be fundamental to getting the correct squish height. Measurement on a used Goetze head gasket suggested compressed height around 1mm = 40 thou. If this is correct, I would deck the block to have piston rims flush with deck at TDC for 40 thou squish height after assembly.
Dick Prince ovlov.net

[mikep]

A form for those who might build a few engines:
(I use a much shorter one)
http://www.buicks.net/shop/engchart.html

Quick, easy to read "no-brainer" on clearances:
http://www.racersoutlet.com/pistons.htm

Dick, I agree with your .040" thickness, very typical thickness, it seems. 0 deck height should work. I have gone closer on small bore/short stroke before, but never less than .025". If necessary, just use clay and an old gasket of same brand as your new one, to mock up clearances. I use a lot of clay. Smear a little grease on the free surface to prevent sticking. Works great for piston to valve, too. Sorry if I am being reduntant.

[Anonymous]

Dick...my understanding is that the OE HG, and the Elring HG, are 1.25mm/.049in compressed...I have seen the compressed value also given as .047in. When I have actually measured used ones, the thickness came out to be between .047 and .049in...and am pretty sure those were OE or Elrings. I think that I will try to really precisely measure the next few I tear down; just for the heck of it.

I usually use either OE or Elring; only tried Goetze once; it worked ok. I have had no problem with Elring's HGs [and one of my suppliers carries the Elring sets]; so haven't felt any need to try a different brand...YMMV

HTH...

[Anonymous]

I actually emailed Elring on this one, they told me the HG for a B23 was 1.30mm new, 1.20mm compressed. They might be 1.25mm compressed-then-removed. I use the 1.20 number 'cause if it's really closer to 1.25 when compressed, that extra .002" isn't going to hurt anything (where .002" tighter could)

[Captain Bondo]

Ya, agree w/ matt. They (Elring) list their gaskets as 1.2mm and 2.0mm

[iadr]

I don't think I ever posted these pics to mull over. They are two photos of a very successful high velocity Ford 2.3 head. These were posted by SWB (Sean) @ the Endyn board. I think it's his work. Flow and velocity were balanced to give better acceleration than other heads which had better flow bench figures. Overall radically different than the Volvo. Note how close the chamber walls come- only part of that is related to the canted valve. Note the interesting way that the seat is cut into what would otherwise be a continuous surface on the intake shortside (you don't see seats per se, as this an iron head). Note how the intake short side looks like a 405/531, not at all like small port Volvo :wave: : (there are two photos)

http://www3.telus.net/public/iadr/V/porting%20pics/20039423215_no-4-chamber.jpg
(note that th rectangular opening is not the port entrance. that's a water passage)
Port entrance here, with floor filled with "Devcon Liquid Aluminum" brand epoxy:
http://www3.telus.net/public/iadr/V/porting%20pics/20039423116_inlet-port-1.jpg

I think I posted the below to some thread, but a review seems it wasn't this one. They are counter intuitively positioned- the left hand one is the newer one. I thought it very interesting how this Ford V6 design went from an extremely Volvo-like chamber to a more sophisticated tight chamber, for better power and lower emissions:
http://www3.telus.net/public/iadr/V/porting%20pics/4.0_Ford_chambers.gif

I'm sort of thinking these 3 photos echo Stealth's latest post implying that the need for chamber unshouding might be overstated.

[Captain Bondo]

Notice the big change is in the wall OPPOSITE the sparkplug though. It seems like removing material from any area nearer the plug than that should have little effect...? The major difference is that the chamber wall opposite the plug curves juts right out in between the balves instead of just being straight. I think that is the major difference.

[iadr]

The quadrant which kept with the largest radius appears to be the one opposite the intake port. This would most likely be to prevent wash down of fuel droplets from an injectors spray.
In other words, I don't think the contours are designed around the spark plug position- to say "everything but the fuel spray area area is tightened" might better reflect the design.

[mikep]

For swirl, leave the intake shrouded 30% or so, for turbo, deshroud no more than .25" from the exhaust valve at max lift, with a bowl-shaped taper(funnel).

[Anonymous]

Ian...thanks for the pics. Fast Burn: one of the keys to max BMEP.

After I saw those pics early this AM, I stopped and had to reread the thread. Had forgotten that all this was in this past year: seemed like forever ago.

In review, I'd say that I would have written things a bit differently, if I were to tackle it now. But what is, stands...the good; the bad; the ugly.

Cappy, I hope that you can get the squish as tight as possible with a copper HG...

I am not going to try to convince anyone about the validity or efficacy of the closed chamber aka fast burn. That is something each will have to figure out for himself. The predominant notion of needing to open up the CC to make power has been the 'rule' for too many for too long. Every time I stop by Summit Racing, I make a point to stop by the cylinder head display...just to look at the fast burn CCs. When I build another motor for my truck, it will have a pair of those heads, flat tops, and very tight squish.

What the pics Ian posted say to me is:

...big CCs are not necessary for big power.

...small burn chambers and short burn time are very beneficial.

...directed flow and optimizing the squish areas and squish effect are worthwhile objectives.

Looking at that first pic: the flow past the intake is directed towards the center of the cylinder; they did not unshroud all around the valve for max flow. They kept the squish shelf at the back of the valve near the cylinder wall. One can visualize where the flow goes. The way the valve seat is a valve seat and an anti-reversionary step is also neat. And the pic looks like they wanted to keep the size of the CC as small as possible to keep as much squish shelf as possible. It strikes me that their view of the CC is that it's most important job is to be an efficient burn chamber; and that smaller is better. Flow was accomodated; but in a directed manor, not randomly by wholesale unshrouding. That is nice!

*****

To summarize my viewpoint without intention to 'dis' others':

I do not 'see' a need to remove material in the CC if that removal does anything to reduce the squish effect. I do not 'see' any need to unshroud the valves. I do not 'see' a need to hog out the intake or exhaust ports for more "flow". Why? I use a turbocharger to force the air in, not 28"hg; and I want the smallest burn chamber/fastest burn time I can get. Which means that I do 'see' the need for max squish area/squish action/squish effect. I can see port work to aid in directed flow; and to accomplish uniform flow behavior among the cylinders. If my four cylinders can flow in and out the same, I will use my turbo to stuff all the air in there that can possbly be stuffed. And I will do my best to make sure that the exhaust gases can 'get the hell outta Dodge' as quickly as possible and with as little restriction and backpressure as possible to drive the turbo.

I do not 'see' the SOHC head as being a piece of crap that has to be reworked in order to make power. To the contrary, I see the SOHC head as being pretty d##n good as is: an excellent overall design with swirl built in via the intake port approach. I see the SOHC head as having four identical layout intakes, CCs, and exhausts all in a row. That makes it a lot easier to actually make sure that they are the 'identical' same in size, shape and flow; none of that reversed arrangement or siamesed ports crap. I do 'see' where the CC could be better in the context of the Fast Burn configuration; but I am not ready to whip out the TIG welder just yet: tightening up the squish clearance can make up for some of that.

I do see the exhaust manifold and turbo sizing as my main impediments to power. And you can add the T cam to that list as well. And until those impediments are removed or minimized, I do not see valve sizes as being something that has to be changed. Nor do I 'see' any need to go hoggin' out the ports for more flow until I can really flow the exhaust gases once they leave the exhaust port. Why worry about upping the exhaust port flow when that exhaust gas is just going to be stuffed into a sardine can of an exhaust manifold; where it is so restricted, slowed down, and compressed to the point that the pressure inside the exhaust manifold can reach THREE TIMES the pressure in the intake manifold? I do not 'see' any sense in that. After I fix those things, then I'll worry about any deficiencies that the stock head might have.

But...that is just me and how I see it.

For y'all that think that your cylinder heads need major rework, that's cool....do what you think you gotta do. I will watch and listen...as respectfully and as quietly as I can. Because I do not have any problem with analyzing how things are done or accomplished, such as the hows, whys, and wherefores of cyl head mods...that is interesting stuff to know. And I like knowing the hows and whys of things. And when I get to the point that my cylinder head is what is holding me back, then I'll have a very good idea of what I might need to do.

[245gti]

Well said Stealth. I have to agree. You can add, to you list of "I don't see's", an oversized throttle body. I saw very little benefit, if any at all, when I was running that monster BMW throttle body. It's now sitting on a shelf in my garage waiting for the day I correct a "bunch" of other things. Maybe, and only maybe, then it will be of some benefit....

[mikep]

If your exhaust pressure is that high, you have the wrong turbo/cam/engine combo.

[iadr]

Ok, what if.... you took a 405 chamber (which is bigger around exhaust than small port one, It's pictured here with a 38mm valve) and welded a bit on the side opposite the plug, and a little ridge at the plug. Excuse my lumpy "photochopping". From this:
http://www3.telus.net/public/iadr/V/porting%20pics/chamber2-non8.jpg
to this:
http://www3.telus.net/public/iadr/V/porting%20pics/chamber2-8.jpg

Yeah, I know welding can change the metallurgy, but just say I could deal with that...
Where would this get us?
It sure looks a lot like "everyone else's" chambers now...
More (~20%) squish area, less reversion allowing a bigger cam. Perhaps similar flow. Thoughts?

[mikep]

Looks OK, I still would like .25" clearance around the exhaust.

Some tips I stumbled across:
http://www.speedomotive.com/Building%20Tips.htm
I searched for exhaust valve temperature in dogpile, and hit the motherlode of articles.

*also
http://www.popularhotrodding.com/tech/0311_phr_power_squeeze/index.html

[Anonymous]

Ian...interesting possibilities with a CC shaped as you illustrated.

Before welding the heck out of a head, perhaps doing up a clay or casting resin prototype to play with on a flowbench with a swirlmeter might give indications of what would work. The extra "metal" that you added in [in the pic] should not hurt flow much, if at all: the incoming air already has a 'guideway' past the sparkplug. [The volvo intake port is tangental; contributing to good swirl, and already directing (in conjunction with the valve stem axis being perpendicular to the deck) the flow towards the plug.] The extra metal added would assist in fast burn; and if shaped well, should only assist further in directing the flow to enhance swirl. AND the extra metal would improve the squish area and squish action. I like your illustration. And I do think that the shape of the CC as you illustrated is "where the action is". Or, perhaps better stated: where the action will be.

Dale...yes sir: there are a lot of things that would fit on a "I don't see..." list. Such a list could be fun to compile; and probably irritate the heck out of some people.

mikep....how is that so? how would changing the turbo, or changing the cam, or changing the "engine combo" do anything to reduce exhaust pressure pre-turbine[ aka EBR]??
I ask that seriously...not as a smug smarta$$. I want to know. And, I am also curious as to how unshrouding the valves will contribute to maximizing BMEP.

Unshrouding the valves in the SOHC head reduces the squish shelf built into the head. That reduces the squish area; reduces the squish action; and increases the burn time. It also increases the heat load on the piston crown above the wrist pins; caused by the loss of the boundary layer cooling effect at the ring lands directly above the wrist pins due to reducing the squish shelf of the head right above the wrist pins. This causes uneven heating of the piston crown, leading to heat stresses of the piston and wrist pin areas; and also does not help the ring lands themselves, or the rings to remain at even temps all the way around. The wrist pin areas already get hot as heck; that is why the pistons are machined in an oval below the ring land areas [the narrow part of the oval being at the wrist pins], to allow for the expansion that is going to occur there due to the heat. Why exacerbate that problem?? Why make it harder for the ring lands and rings to maintain their positioning and operation by artificially increasing the hot spots of the piston structure? Why reduce the boundary layer cooling above the two areas of the piston that are going to get hotter than the rest of the piston as a matter of course? For more flow? Not a justifiable reason from a piston durability, ring land stability, or a ring sealing viewpoint.

The cooler, and more uniformly cooler, you can keep the piston crown and ring lands, the better the rings can can do their job to seal. Good tight squish helps do that [boundary layer cooling effect/heat transfer]. Small burn chambers help do that. Shorter burn time helps do that. And all the above helps optimize BMEP. [and much of this is discussed priorly in this thread]

Flow is an adjunct to making power. Flow is not the source of power; it is a helper. It is BMEP that makes power.

Thoughts?

[mikep]

You can have very high BMEP with dirty air. A funnel shape can help evacuate the cylinder, leading to higher oxygen content in the cylinder.
More air out, smaller turbine, and oversized compresser each contribute to higher exhaust pressures and less evacuation.
Cam timing can have a great deal of impact on exhaust pressure, and a late exhaust closing event on a high pressure turbo can let exhaust back in the cylinder.
In a high performance NA engine, good overlap and good exhaust scavenging can help suck air in the cylinder, creating enough momentum for a true ram effect as the exhaust valve closes. This is the reason for higher than 100% VE in many race engines.
The engine combination includes every angle in the runners, valves, seats, piston dome, everything. And exhaust pressure needs to be looked at from the end of the power stroke to the time it leaves the car. All stages on each side of an area create pressure differences that do something good, bad, or negligible.

I might weld up a head just to study the strength concerns. A small quench pad should help, but with a dished piston there is less piston to work against a large pad. Flame propagation still starts on the side, but the pad across from the plug will shorten the burn across. If the burn gets there before the piston in moving fast, it will burn more completely and give more pressure at peak leverage, with the crank arm at about 90 degrees.
The higher a compression ratio is, the quicker the pressure drops as the piston moves down, so this is important with NA and LPT apps.

[Captain Bondo]

I actually can't agree on many of these points. Volumetric efficiency is every bit as important as a good burn. Sacrificing ve in order to have a chamber that withstands a high bmep, and then force feeding it tons and tons of boost to actually develop those cylinder pressures becomes false economy in real world conditions. I would say its easy to swing the other way. Avoiding uunshrouding? sure. But ignoring proper port shape and intake format just for the sake of snubbing your nose at flow when port shape will have little to no effect on burn rate? I think that is just being "anti" for the sake of it.

Just trying to balance the equation.

[Anonymous]

Cappy...I am not anti-headwork per se. Nor am I down on VE. Quite the contrary: I want high VE.

Three systems affect VE: induction; the cylinder head; the exhaust system. Each of those 'systems', and all the components that comprise each of those systems, have to work together within each system and also with the other systems to achieve good to high VE.

My point is, and has been, to evaluate where the impediments to power building are, from both the VE and BMEP aspect viewpoints. Looking at the three systems affecting VE, and trying to determine where the priorities should be placed in order to improve VE, but without degrading BMEP (by that I mean good burn rate/time and all the things that tight squish etc can deliver) has led me to many of the conclusions and views as stated priorly.

Looking at the 'stock' arrangements of the three systems, I see things that definitely merit attention and improvement...in each of the three. Where I have departed company with the conventional wisdom among most of the boosted motor enthusiast crowd is in what can and should be done with and to the exhaust system to improve VE and contribute to BMEP.

Why so? In my analysis, the system that has the greatest needs for improvement and enhancement is the exhaust system...the manifold, the turbo, the downpipe, and on back. The 'stock' exhaust system is, as I see it, the weakest link, or the greatest impediment, in the quest for high VE and max BMEP.

Does the cylinder head merit attention? Certainly; but not first--and that is my opinion. And what I was trying to get across with my last post was that many of the 'standard' mods to a cylinder head, unshrouding for instance, have good effects and bad effects that need to be evaluated.

And Cappy, you are correct: "balance" is the key word. Balancing the good effects vs the bad effects that certain mods can result in. And, balancing how each of the three systems work, internally in each system, and with the other two to deliver high VE...and high BMEP. My view of the balance is that the stock exhaust system is not in balance with the other systems. Once I have raised the exhaust system's performance to equal or exceed what the stock head and induction systems are doing, then I'll work on the head, and on the induction system....strengthen the weakest link first; then enhance the stronger links...

To those who have approached it from the 'headwork first' corner, I say: fine; great; cool; wonderful.......now get your butts busy and get the exhaust system improved to the point that you will actually benefit from your headwork...and I say that in an encouraging and positive manner...

mikep...what you say ties in...I think we see things similarly; probably more of a semantics thing in how we express it...[that's cool; and part of the fun]

[Canuckvolvo]

Ah, gotta love this thread...

Stuff Matt Dupuis and I were just talking about yesterday- where's the balance? Not in this thread of course, but in the engine. I'm in the process of cc'ing my head and trying to figure out what the best balance of compression ratio vs. quench pad vs. all the other factors is.

So far, I figure I need to get my CC's to about 56cc's if I want my CR around 9.1:1. Don't ask me why I'm picking 9.1:1, it just FEELS right. I basically have removed material across from the plug where there is no quench action from the dished piston. This has taken me to ~54cc's so I figure a little valve unshrouding (think I'll use that 405 chamber shot for a template) should do the rest, figuring that the small amount of quench pad lost will be more than offset by slightly better flow out the exhaust in combination with a slightly less volotile CR.

Probably splitting hairs at this point, but am I right in assuming that, all things being equal, I'll have slightly more power(boost) potential by going this route as opposed to leaving it right now at ~9.3:1? Bah, I suppose it all depends on the quality of my own damn work too...

By the way, I'm planning on sticking with the stock injection (LH 2.0 from the B23FT) for now, probably trying larger injectors at some point...

[Captain Bondo]

The b23ft lh computer swap works good athal, just as a sidenote.

I hear you Stealth. I would agree as well, just thought I'd point out for others that an engine with 120ish NA hp is an engine with 120ish NA hp with or without a good burn so even if it will take a high BMEP, the 30+psi you need to force feed it to overcome all of the pressure drops is less than ideal. ;)

Definitely agree on the exhaust stuff though. It really makes sense that with a turbo, the tough part is not getting the gases in, but getting them out. Good stuff.

On another sidenote to Canuck, I am running flattops in a b23 with a 405, and am looking at cr lowering in a similar way. I think the best way to help lower static cr a bit without killing the burn is to make the chamber deeper- take out all of that nasty, rough casting stuff oin the roof of the chamber. You should be able to increase cc enough through this and just a mild unshrouding. A nice benefit of removing that nasty rough stuff from all 'roud the valveseats is that it removes what is most likely a nasty source of hotspots.

It's what I'm gonna try anyways. lol

[Boris740]

A nice benefit of removing that nasty rough stuff from all 'roud the valveseats is that it removes what is most likely a nasty source of hotspots.

It's what I'm gonna try anyways. lol

This is how mine came out.

http://www3.sympatico.ca/borism/Headwork/Inhead.jpg

More pix at http://www3.sympatico.ca/borism/Headwork

Not really visible in the pictures is the intake unshrouding that I did by carving out the side walls a round the intakes into a "C" or more of a semicircular profile instead of flat sloping walls. The idea was top promote swirl. Kind of hard to describe but it lets me run 17 lb of boost on 94 octane.
If I lean into it will have occasional knock. I am thinking of eventually incorporating the Knocksense into Megasquirt. Once I incorporate the Megasquirt of course.

Other stuff at http://www3.sympatico.ca/borism

[Canuckvolvo]

Interesting. Is it just the camera angle, or is that a big honkin exhaust valve? I'll be taking some more pics this weekend. What do you figure your final CR is?

[Boris740]

Interesting. Is it just the camera angle, or is that a big honkin exhaust valve? I'll be taking some more pics this weekend. What do you figure your final CR is?

Regular valves. Closeup will do this. As far as the CR goes maybe someone can figure it out for me. I eather do not have enough info or maybe I am just stupid.

The old 530 head has the head chamber volume of 52.2cc
The new 530 had has the head chamber volume of 56.0cc

I am trying to figure what my new compression ratio is. I know that
B230FT has the compression ratio of 8.7:1 but this is where I start to
stumble. I do not know the total volume that the piston displaces nor I
know the volume between the top the head gasket line and the piston when at TDC. Heck I don't even know the proper terminology :e-shrug: Any ideas?

[mikep]

bore-96mm/2=48mm(4.8cm)^2= 23.04 x 3.14= 72.3456 sq.cm
72.3 x 8cm stroke= 578.8cc x 4= 2315cc.
I was not worried about rounding.

1mm gasket= 0.1cm x 78.5sq.cm= 7.85cc gasket.

assuming a 0 deck height piston, w/flat top piston,

BDC= 578.8 + 7.85 + 56 = 642.65cc
TDC= 7.85 + 56 = 63.85cc

642.56/63.85= 10.065:1 compression.

Measure your dish and deck height, and there you go.
BTW, this is what my B23 works out to with the exhaust deshrouded for a B21 block.

[Boris740]

bore-96mm/2=48mm(4.8cm)^2= 23.04 x 3.14= 72.3456 sq.cm
72.3 x 8cm stroke= 578.8cc x 4= 2315cc.
I was not worried about rounding.

1mm gasket= 0.1cm x 78.5sq.cm= 7.85cc gasket.

assuming a 0 deck height piston, w/flat top piston,

BDC= 578.8 + 7.85 + 56 = 642.65cc
TDC= 7.85 + 56 = 63.85cc

642.56/63.85= 10.065:1 compression.

Measure your dish and deck height, and there you go.
BTW, this is what my B23 works out to with the exhaust deshrouded for a B21 block.

Well that's a start. Thanks. Does anyone know what the dish volume and the deck height is for a 91 B230FT? My pistons are in my engine at the moment.

[Canuckvolvo]

Using the handy calculators at http://www.pontiacracing.net/calccr.htm

You can fudge some numbers to get your base CR of 8.7 (concensus is HG is 0.047" or 1.2mm thick compressed, assume 0 deck height, dish is somewhere around 12cc). Tbricks specs page lists 530 head at 51.7cc's so your 52.2 is close enough for aruguments sake. Change it to 56cc's and your CR goes to....(assuming you didn't deck the block or use oversize pistons)

8.3:1

That would certainly allow you to run higher boost than stock.

[Anonymous]

For reference purposes, I'm posting this here:

...am doing a 90 B230FT for a DD; the deck height was +.004in. And the bores are STD [C-D-D-E]; the block was not touched in 190K, although the head was, and it is junk. The rods are the 13mm rods. [I have 2 other 90 FTs to tear down sometime; and will post their deck heights and rod sizes at that time.]

With a +.004 deck height on the 90 block that goes to the machine shop in the AM, I'll have to wait to see if the mains need line'd or not; and if the rods need resized or not. [the crank needs a grind to 1st US, so I can get my one and a half thou clearances: they're pushing three right now] Then we'll figure how much can come off the deck to end up with the squish I want. fun fun fun After a hot tank and mag, the bores should clean up nicely at 1st OS [they are less than .002in OS; with no egg/taper; and little belling; the ridge is less than .004in]; and I have a set of 1stOS ET pistons for it. will set the piston clearance to .0010-.0012in...[I hate slap].

[Canuckvolvo]

Block is back from the shop, should be about 0.010" above deck when assembled. Crank is out for 1st US machining, just waiting for gaskets and bearings to arrive from FCP. I've got the head almost ready, all chambers to within 0.5cc but I think I can do a little better. Should be right around 9.1:1 when all is said and done, just don't ask what the piston-bore clearance came out to...gonna be a little slappy :oops:

[Boosted2003]

Comdo bondo what your talking baout is getting ot group a specs head form europe u cna get oen shipped made out of 405 head for 1200 to US.....

[MikeHardy]

you used to be running about 8.86 on your old head, must of shaved it a little.

but with 56cc and 0 deck hieght your comp should 8.47:1

[Anonymous]

Block is back from the shop, should be about 0.010" above deck when assembled. Crank is out for 1st US machining, just waiting for gaskets and bearings to arrive from FCP. I've got the head almost ready, all chambers to within 0.5cc but I think I can do a little better. Should be right around 9.1:1 when all is said and done, just don't ask what the piston-bore clearance came out to...gonna be a little slappy :oops:

I would suggest then that you have the pistons knurled. Then hand fit each one to its bore...BTDT...you can end up with good and snug piston clearances. Less piston rocking is good for ring stability and to keep the piston crown away from the head at TDC.

A good machinist, familiar and capable of performing the knurling operation, can get you about a plus .008in diameter on the skirts.....the hand fitting can end up better than plus .004in.

Two US companies made knurlers; Hastings and K-Line. There may have been others; but I am not aware of them. I have an older Hastings unit, and a K-Line. I prefer the K-Line. I will be doing a 91 FT with the K-Line, to drop the 91 into my 90 765T.....just for the S&Gs of it....and to show that knurling is viable for the tuna can pistons in the 230s. I already know how well it works on a 21FTi: excellently.

[mikep]

Knurling is also done to trap oil on the pistons, improving reliability in some engines. Detractors claim that knurling aluminum leads to cracking, but I have not seen evidence of this.

I personally set up performance engines loose for myself, for low friction and a little more cushion on the resistance to scuffing/galling. (+.001" on average)

[Canuckvolvo]

Hmmm, I will look into knurling, probably worth while since I've done everything else "right" so far. Depending what specs you believe, Volvo called for anywhere between 0.0012 and 0.004" clearance for forged pistons. I'm running pretty close to 4 and there's a couple of out of round spots that are ~0.006". Given the cold winters here, I'm thinking tighter clearances would be better, more like 0.002". Just hope someone in town can do the knurling for a reasonable price...

[mikep]

Forgings really need to be loose, but .004" is pretty much the max.
.0012" sounds like a casting.
Is the difference in the piston or the cylinder?

[Canuckvolvo]

cylinder, pistons are new.

Both haynes and chilton list cast pistons in the 0.0004-0.0012" range and "some versions" (assume forged) units in the B23E and B23FT listed at 0.0012"-0.004" IIRC

[mikep]

OK, so the out of round spots are just normal cam-ground piston differences.

[Anonymous]

yes, the clearances for the B230s are 0.0004in-0.0012in...

...that is less than half a thou to just over one thou [1.2]...if you were to run a B230 at 0.004in [4 thou], you would be listening to piston slap til hell freezes over...in fact, the green manuals say that if the piston to cyl wall clearance is measured at .004in, it is time to bore to next size up. [I guess they'd rather sell more pistons; rather than promoting knurling] This refers to B230s; would have to dig out the book on 21s/23s to see what the book says for those blocks. This is all in reference to OE pistons. What you'd do with AM forged, I will yield to what I recall Mike Aaro saying: 2.5 to 3 thou....if I misquote Mike, my apologies.

Canuck...if you have 4 thou piston to wall, please knurl them... 4 thou is very much within what knurling can give you...and as mikep said, knurling is used sometimes to help trap oil on the skirts...

I just spent a couple of hours going over all this info again with my machine shop...and yes, I did bring the binder with the green manual pages [in page protectors] in it for them to use. Once they see it in black and white, they go: 'cool'. I will be getting my B230FT block back with one thou piston to cyl wall clearances...which is exactly what I want.

If I get a chance tomorrow, I'll check my green manuals for the 21s/23s and post the clearances. I don't trust aftermarket manuals.

[EricF]

Just figured I'd throw it in, have the green manuals sitting next to me...

B21A/E/F - .0004 - .0016 in

B21ET/FT - .0008 - .0016

B23A (?) - .0004-.0016

B23E (80.4 mm bore piston) - .0019 - .0028 (type 1)
'' (76.4 mm '' '' ) - .0004 - .0016 (type 2)

B23F - .0004 - .0016

[Anonymous]

EricF...thanks for posting that data. If I may, I will make a correction/clarification ; and add some more data:

...the data you listed for the two types of B23E pistons refers to the total piston height, rather than the bore.

B23E type 1 pistons are 80.4mm tall.
B23E type 2 pistons are 76.4mm tall.

I went and found a couple of green manuals: "New Car Features: 760 Turbo 1984" and "Section 2 (21) B19. B23 engines 740/760 1983-1984 Reconditioning".

From the Recon manual, the following:

Piston running clearances:
B19E, B23E......0.01-0.04mm / 0.0004-0.0160in
B19ET...........0.03-0.06mm / 0.0012-0.0024in
B23ET, B23FT....0.05-0.07mm / 0.0020-0.0028in

This says that the forged pistons in the B23ETs and the B23FTs do run a tad looser than the reinforced cast pistons in the B21ETs and B21FTs. My Mahle Big Book does not list the B19ET; therefore the pistons were probably supplied OE by Kolbenschmidt. From the clearances listed, they may have been forged; but I cannot verify that either way.

From the New Car Features manual:

B23FT data:

Crankshaft: forged steel; case hardened
Con Rods: drop-forged steel
Pistons: forged from aluminum alloy; externally plated with thin layer of lead for improved break-in characteristics....

"The pistons are of the Duotherm type: the piston crown and skirt being separated by a steel insert. In this way the transfer of heat from the crown to the skirt is reduced. The piston consequently does not expand as much and the piston side play can be made less without the risk of scoring."

Piston pins: "The position of the piston pin is approx. 1.5mm (0.06in) off-center."

...meaning that the wrist pins are off-set away from the thrust side of the piston. This is one of the goodie tricks to improve power transfer from the piston to the rod to the crank. It also reduces the side loading of the pistons onto the cylinder walls. Not too shabby for a "stock production" motor, eh??

*****

The reasons why I wanted to post this data ties back into the factors that affect how tight we can set the squish: rpm redline [rod stretch], and piston rocking [affected by piston to cylinder wall clearances].

It is obvious that I advocate running tighter wall clearances; and I do. That does not mean that I pooh-pooh mikep's preference of an extra thou for a performance motor. I would tend to agree with the validity and reasons for his approach...for a "performance" motor...or for one that someone is gonna wind out a lot on a regular basis. Then they need to set squish height with that in mind.

A possible way to have both tighter wall clearances, and reduce chances of scuffing, might be with an application of dry film lubricant to the piston skirts. And, knurled skirts do help hold oil on the skirts as well.

[mikep]

...preference of an extra thou for a performance motor. I would tend to agree with the validity and reasons for his approach...for a "performance" motor...or for one that someone is gonna wind out a lot on a regular basis. Then they need to set squish height with that in mind.
Oh, yeah.
...A possible way to have both tighter wall clearances, and reduce chances of scuffing, might be with an application of dry film lubricant to the piston skirts. And, knurled skirts do help hold oil on the skirts as well.
And, don't forget the fancy coatings.
http://www.swaintech.com/race.html
http://www.cecoatings.com/specialty.html
http://www.hpcoatings.com/engine_coatings.htm

[Canuckvolvo]

Thought I'd bring this thread back up since there's a few engine rebuild questions on the main page. Oh and to show off my head;)

http://groups.msn.com/_Secure/0VADSAtMa45W!JAZNTfe35!MKOHGWYMBL8q!QWAgN3YIgqKdch AdYRAfy2Nv9m9NR20xHHcXIenPmHIdo63kZa7pYMBAxCfd8lwt IxpspDMD24DT3zbrhKQP!EhMeC!xt/polished%20chamber.jpg?dc=4675448696280538251

After all is said and done, the chambers are right around 57cc, a little more than planned, oops. My piston-deck clearance didn't come out quite as nice as planned either, about 0.003" proud, not the 0.010" I wanted- not sure why. So squish won't be as tight but :e-shrug: what can ya do. Final CR should be righ around 8.9:1 and squish height ~0.042".

So, not perfect, but better than stock anyway! Assuming my head work doesn't do more harm than good :x:

In the home stretch! Now my garage is nice and insulated, maybe I can finish this thing before Christmas...

There do seem to be some discrepancies on piston specs. Has anyone had a shop check the B21, B23, B230, B234, Penta AQ 151, and Penta AQ171 pistons to see which are cast and which are forged? And, further, what alloy they are made of if forged?

I did ask my shop about the B230FT pistons and the shop did say that they were cast. The shop also said that as cast pistons go, they were pretty good ones. However, the shop also said that forged pistons would be better for a high boost motor (by high, I mean one that will see 15-22 psi in daily driving and that may see 22-29 psi at the track). The shop could not locate any drop in replacement pistons that were forged, so we had to go with aftermarket.

I have a Penta AQ171C with a fresh stock rebuild. It has Mahle pistons. There are some numbers stamped into the piston top. I'll try to copy them down and post them here so Tom can look them up in his big Mahle book. As I recall, someone communicated with a Mahle representative and was told that Mahle did not make any forged pistons. I guess that I will be going aftermarket again when I build this motor for boost.

On OEM and aftermarket forged pistons, there are generally two types, 2618 and 4340, referring to the alloy. The 2618 are tougher but have the higher expansion rate and need more clearance. These are the pistons that make a lot of noise when cold. The 4340 have silicon in them and are less rugged but still more so than cast pistons. They need just a bit more than stock clearance, like in the .003 to .005 range. I am likely to go for 4340 when I build up the AQ171.

What have people learned on OEM cast and forged versus aftermarket forged pistons?

Philip Bradley

[Anonymous]

As I recall, someone communicated with a Mahle representative and was told that Mahle did not make any forged pistons.

Horse puckies. Mahle makes all kinds of forged pistons. Or are you saying that Mahle doesn't make forged pistons for a B230-based Volvo? I believe that's true...

Dale's got a Mahle catalog, and there are only a couple forged pistons for a Volvo. One is the B23FT/ET flavour, and one is the B23E "sport" piston. They list the AQ 151 as being cast, but they don't list the 171 at all (they have the B234, though... IIRC.)

I'll get him to chime in here a bit later with that information.

[mikep]

Mahle even makes F1 pistons.

[Captain Bondo]

Ya, I remember going through some piston ideas with Dale regarding Mahle, and the stock B23ft (forged) are mahle, and the 94mm Ford Cosworth YB pistons are forged mahle as well.

B23e sport pistons eh? Forged flat tops for the b23e sound like Fun with a capital "F"!

[245gti]

Here are some scans of the Mahle catalogue. Unfortunately, the binding bends the pages up so the applications are a little fuzzy. All the specs are there though along with part numbers.

http://68.101.32.25:5555/pictures/volvo_pics/diagrams-sketches/Mahle%20Piston%20Materials.pdf

http://68.101.32.25:5555/pictures/volvo_pics/diagrams-sketches/Mahle%20Piston%20Types.pdf

http://68.101.32.25:5555/pictures/volvo_pics/diagrams-sketches/Mahle%20Volvo%20Piston%20Listings.pdf

http://68.101.32.25:5555/pictures/volvo_pics/diagrams-sketches/Mahle%20Volvo%20Piston%20Listings2.pdf

http://68.101.32.25:5555/pictures/volvo_pics/diagrams-sketches/Mahle%20Volvo%20Piston%20Listings3.pdf

Patience with the pages loading....

[Anonymous]

Canuck...looks nice...smooooth. I'll be reporting on the tight squish/hi CR 230FT in process late next week...with pics available.

Philip, if Dale or someone does not do it in the meantime, I'll put together the info on the pistons at that time. Only the B23ET/FT and B23 "sportversion" flattops were forged; all other ET/FT pistons are the 'better' grade reinforced cast; as are the mahle's in your penta: letter "v" cast in the underside of the skirt [next to some other numbers] denotes "autothermatic/hydrothermatic" grade.

And I see that Dale posted some pages from the big book...Thank you, Dale.

[towerymt]

I've got a box of B23FT pistons, new, standard size, p/n 037 59 00, 95.95mm+0.06=96.01. They match the picture of the forged type pistons. Very thin and straight skirts, and very open on the underside. I noticed those catalog scans list both the B23ET & FT at 9:1 CR. Anyone know how to tell them apart?

/B23FT_piston.JPG (http://mason.gmu.edu/~mtowery/volvo/B23FT_piston.JPG)
/B23FT_box.JPG (http://mason.gmu.edu/~mtowery/volvo/B23FT_box.JPG)

[Chad242ti]

From memory, my ET pistons had a more shallow dish than the FT ones you show in the picture. You may be able to contact Mike Aaro, he would be able to give you the exact bowl difference.

I think the main reason that the dish is shallower is due to the fact that the ET engines came with the 405 or 531 head. The 405 and 531 heads both have larger combustion chambers than the standard 389 or 530. In order to maintain the higher compression ratio Volvo had to make the dish in the piston less deep. So the FT pistons with the 405 or 531 head would yield a lower compression ratio than 8.7:1, and ET pistons with the 389 or 530 head would yield a higher compression ratio than 9.0:1. Maybe somewhere close to 9.3:1... :e-shrug:

Other than the dish, I believe my ET pistons looked almost identical to the ones you have. My new ones of course were the next larger size than stock due to some cylinder wear... Best of luck with the engine build up. :x:

[Captain Bondo]

I'm not sure I'm reading it right, but it looks like the forged flat top "sportversion" are even availible in overbores- is that right?

As far as ft vs et go, I think ft have a 5mm dish and et have a 3mm dish.
about 12cc vs 8cc I think.

[Anonymous]

Cappy, you read it right: the sportversions are available in STD, 1st and 2nd OS.

Michael, there are two pistons listed for the "B23FT"...
...P/N 037 59 00 (STD) listed for both 23ET and 23FT has the wrist pin diameter of 24x72mm [the B21/23 size]; the piston has total height of 80.4mm; the dish is 2.3mm deep; and the compression height is 46.4mm [the distance from the wrist pin centerline to the top of the piston].
...P/N 037 79 00 (STD) listed for the B230FT {????} also has the 24x72mm wrist pin...meaning that it HAS to be a B23 based motor. That piston has a total piston height of 75.7mm; the dish is 4.4mm deep; and the compression height is 46.7mm.

The differences are the total height; the dish depth; AND the comp height:
...the 037 59 00--the ET piston-- is a taller piston, with a shallower dish; BUT the piston does not come up the bore as far. It stays [.3mm] (.0118in) farther down in the cylinder than does the 037 79 00 piston. The shallower dish of the 037 59 00 is more than offset by its shorter comp height. The 037 79 00 will have tighter squish than the 037 59 00, if they were installed and measured in the same block. Yes, the block deck could be milled to tighten the squish for the 037 59 00s; but my point is that just comparing dish depth is not the whole story: you have to look at dish depth AND comp height to get the complete picture. A shallower dish does not automatically mean higher CR. The compression height and installed deck height is the final determiner of CR; the dish depth is secondary to those dimensions. I was confused by the reports of there being a difference between the US B23FT piston dish depth and the B23ET dish depth, when the catalog says that the same piston is for both [the 037 59 00]. The 037 79 00 piston is the US version of the B23FT; even though it is listed as being for a B230FT. The total piston height AND the wrist pin diameter resolved the mystery; B230 /B234 wrist pins are 23x65mm.

A little sidenote: if you look under the part number--037 59 00--, you will see "96 P 10": that is what you will find cast into the underside of the piston: on the skirt, or under the crown. The "P" is for "forged". "V" is for "autothermatik/hydrothermatik"; "D" is for "duotherm".

Another sidenote: Volvo did list the forged pistons for the B23FT as being forged, but of the 'duotherm' type: meaning that those forged pistons have a steel shell inside to act as a heat shield between the ringlands/crown portion of the piston and the skirt. This heat barrier keeps the skirt cooler, allowing for tighter piston to cylinder wall clearances.

Aftermarket forged pistons--JEs, Ross, Wiseco, etc-- do not have that steel heat shield built in; and have to have a bit more piston to cylinder wall clearance, to allow for the greater piston skirt expansion.

edited "3mm" to ".3mm"
-m

[Anonymous]

Sure, the B23FT and B23 Sportversion pistons are built in oversizes, but you know you're paying an arm and a leg for the relatively common B23FT pistons in oversize, so what's the Sportversion going to cost, if you can even find them?

Wondering what you'd be needing flat-top, oversize, forged pistons for a B23 anyway - eh, Kenny? :wink:

[mikep]

Forgings are struck, and therefore cannot have complex 3-dimensional pockets unless they are machined, which is costly.
Look for: No casting part lines, and fairly straight sides to all walls, particularly the inside of the piston. If it is a crank or rod, the part line will be roughly 1/4 inch wide, as compared to a casting, which will have a skinny, sharp casting part line.

forged piston:
*note* the inside of the piston is the best place to look.
<img src=http://www.billzilla.org/piston-1.jpg>
<img src=http://www.billzilla.org/piston-2.jpg>

cast piston, note the detail on the side, in a rough finish:
<img src=http://www.pbase.com/image/23692914.jpg>

cast piston and cast rod, note the skinny part line on the rod, and the detail in rough finish on the side of the piston:
<img src=http://www.pbase.com/image/23692939.jpg>

[towerymt]

Michael, there are two pistons listed for the "B23FT"...
...P/N 037 59 00 (STD) listed for both 23ET and 23FT has the wrist pin diameter of 24x72mm [the B21/23 size]; the piston has total height of 80.4mm; the dish is 2.3mm deep; and the compression height is 46.4mm [the distance from the wrist pin centerline to the top of the piston].
...P/N 037 79 00 (STD) listed for the B230FT {????} also has the 24x72mm wrist pin...meaning that it HAS to be a B23 based motor. That piston has a total piston height of 75.7mm; the dish is 4.4mm deep; and the compression height is 46.7mm.

The differences are the total height; the dish depth; AND the comp height:
...the 037 59 00--the ET piston-- is a taller piston, with a shallower dish; BUT the piston does not come up the bore as far. It stays 3mm (.0118in) farther down in the cylinder than does the 037 79 00 piston. The shallower dish of the 037 59 00 is more than offset by its shorter comp height. The 037 79 00 will have tighter squish than the 037 59 00, if they were installed and measured in the same block. Yes, the block deck could be milled to tighten the squish for the 037 59 00s; but my point is that just comparing dish depth is not the whole story: you have to look at dish depth AND comp height to get the complete picture. A shallower dish does not automatically mean higher CR. The compression height and installed deck height is the final determiner of CR; the dish depth is secondary to those dimensions. I was confused by the reports of there being a difference between the US B23FT piston dish depth and the B23ET dish depth, when the catalog says that the same piston is for both [the 037 59 00]. The 037 79 00 piston is the US version of the B23FT; even though it is listed as being for a B230FT. The total piston height AND the wrist pin diameter resolved the mystery; B230 /B234 wrist pins are 23x65mm.

Thank you, that clears up a lot. I had trouble making logical sense out of it, though, because you left off a decimal point when writing "It stays 3mm (.0118in) farther down in the cylinder...". The conversion in inches didn't register because everything was in mm, so that's how I compared dish to compression height.

B23FT = 4.4mm dish, 75.7mm height, 0.3mm taller comp. height.
B23ET = 2.3mm dish, 80.4mm height, 0.3mm shorter comp. height

I think I got it now. :wink: The only problem is that the dish, when eyeballed with a ruler, is less than 3mm. The piston sitting flat on my desk measures just over 75mm in height. This doesn't match to what the Mahle specs say I should have. Is the given spec definitely a measure of depth?

[quote:83cd33cdcf]A little sidenote: if you look under the part number--037 59 00--, you will see "96 P 10": that is what you will find cast into the underside of the piston: on the skirt, or under the crown. The "P" is for "forged". "V" is for "autothermatik/hydrothermatik"; "D" is for "duotherm".[/quote:83cd33cdcf]

True, cast into the underside of the crown.

[quote:83cd33cdcf]Another sidenote: Volvo did list the forged pistons for the B23FT as being forged, but of the 'duotherm' type: meaning that those forged pistons have a steel shell inside to act as a heat shield between the ringlands/crown portion of the piston and the skirt. This heat barrier keeps the skirt cooler, allowing for tighter piston to cylinder wall clearances.[/quote:83cd33cdcf]

If they were the "duotherm" type, would it have "96 D 10" instead? How much might the clearance vary between a duotherm piston and a forged piston? I'm hoping to find a B23F block in good condition for my std. size pistons, but if I'll need tigher clearances, I may have to look elsewhere. Overboring a B21 block is what I wanted to do, but cost might be too great if I have to sonic test several blocks to get a good one. I want a quiet and durable engine most of all, and I'm on a tight dollar budget.

Another slow moving turbobricks engine project...

Thanks,
Michael

[Anonymous]

Michael, sorry about the missing decimal point. I thought I had typed it in--guess my glasses need cleaned--; should have typed it correctly: "0.3mm (.0118in)".

I don't have the different pistons for the B23ET and FT sitting around to compare the measurements as you have. According to the mahle book, those are the dimensions for those part number pistons. Perhaps, they changed the specs for a particular part number; or decided to consolidate the two part numbers into one part number for both apps. I don't know if either is the case.

But what you are saying is that the pistons you have are 75.7mm tall, and have the 2.3mm dish. I believe you. I do not know why your measurements conflict with mahle's printed dimensions. The one thing I would suggest is for you to verify what the comp height is on your pistons. Your machine shop will need to know that dimension when they work on the block that you do use, esp if the piston's actual dimensions differ from the printed dimensions. I include copies of the mahle piston dimension/specs/part number pages--like what Dale posted-- in the binder with the green manual for the engine when I take a block to my machine shop. It looks like I will have to doublecheck the pistons in the box against the pages' dimensions before I take them in from now on. And if there is a discrepancy, I'll have to make a note of it.

Re the "duotherm" type...I have a B23FT that I disassembled for evaluation. The pistons are 1st OS; with the "96 P..." underneath. And they have the steel strut visible on the underside as well. [I'll try to find the set and post some pics; and I'll have to measure those pistons to see what they are.] When I saw the steel inserts in those pistons, my reaction was 'WTF?'; then I saw the "P"; and then I went and reread the mahle book; and got out the B23FT books. From what I read, those pistons are forged; and they are supposed to have those steel strut/insert/shell/thingy's in there. [and my thoughts are still 'WTF?' even after reading all that in the books]

Why Mahle would make a "forged" piston with the steel insert, when nobody else does it that way, is a bit baffling. The reason I quoted was right out of the '84 760T new car features manual; stating that the pistons are forged, but of the duotherm type: the steel strut/shell being in there for the heat barrier action. Perhaps the steel insert is something that Volvo wanted for their forged pistons for the turbo motors. The Volvo lit points the steel strut out; but Mahle's book does not mention or illustrate their forged pistons having a steel strut inside. Jeez.

Finding a B23FT block that is not worn to the point of having to go 1st OS is going to be tough; finding a B23 block like that isn't going to be much easier. Overboring a B21 is viable; but yeah, I hear you on the sonic testing cost aspect.

Perhaps, an alternative view: find a B23 or B23FT block that is still good enough that you won't have to bore to 1st OS; but is a bit on the "loose side": like about 0.002-0.004in worn; but still straight and round. Hone it just enough to prep the wall surface for the rings, keeping it under 0.005-0.007in OS. Then, knurl your new pistons to tighten up the wall clearances back to the 0.0008-0.0012in specs [you could do fine with 0.0015-0.002in wall clearance; that'd be a tad looser than my personal pref; but it would work with a '23' tall piston]. This might help you avoid the hassles of trying to find that 'perfect' used 23 block; or the hassles of overboring a 21 block. Knurling new pistons to make up for 'some' bore wear is not a sacrilege; it might be a very cost-effective way to resolve your problem.

[mikep]

Perhaps, an alternative view: find a B23 or B23FT block that is still good enough that you won't have to bore to 1st OS; but is a bit on the "loose side": like about 0.002-0.004in worn; but still straight and round. Hone it just enough to prep the wall surface for the rings, keeping it under 0.005-0.007in OS.
I'm looking as hard as I can for a block for his project and was thinking the same thing.

Then, knurl your new pistons to tighten up the wall clearances back to the 0.0008-0.0012in specs [you could do fine with 0.0015-0.002in wall clearance; that'd be a tad looser than my personal pref; but it would work with a '23' tall piston].
A low-friction coating will also tighten things up.
I am running .004" clearance in my current B23 engine. Looser than my preference. Sounds good, runs great. I would be happier with .003", but whatever. It means less warmup time and more abuse leeway.

[Canuckvolvo]

http://groups.msn.com/_Secure/0UgD6AjoYe9JqyPvwZpxOvbnKduTQIP6hWhMmGyJvf4vJQhdE8 XtHySFdA7khKcTNqsO8LOLTs6zumXF5sMnDe2sKwy0DGDnxvad !1Kb8!bjDD575UO!UVufQuLS*O!ga/B23FT%20side%201.jpg?dc=4675449492438275950
Deck height came out around 0.004" so total squish will be ~0.043". Not the 0.037" I was aimin for, but should be much better than stock!

Extra big thanks to Matt D. for doing most of the assembly while I was insulating the garage. Now that it's warm enough to work out there I can start working on that messy LH2.0 wiring harness....

[Anonymous]

here is a link to my gallery with pics of the 230FT I'm doing for a customer...

the squish will be 0.037in.

http://www.pbase.com/stealthfti/b230ft_engine_parts_pics

[Stereophile33]

I know that one person on the board at a Unitek phase head sliced up in canada....has it ever been determined what Mike Aero was doing to make his heads so special?

I just got through reading this entire thread.....just wondering where we have come on the research in the last 2 years?

[stealthfti]

I just got through reading this entire thread.....just wondering where we have come on the research in the last 2 years?

I can't speak for anyone else, but I know where I am at.

Since it has been almost two years since my last post in this thread, almost three years since Cappy asked the Question, and since no one else has offered a reply to your question, it looks like it is mine to do so.

I'll let Cappy go over what led up to this thread, and his assessment of things since, if he wants to.

Since my last post here, I completed that first tight squish motor, a B230FT/ET, built two more, and contributed a little tech advice on the build up of a fourth one. I have several more in the pipeline, of which a couple will be NAs.

A lot of people look over what is involved, and decide that it either too much like work, or that they can get where they want to go via other means. no problemo.

The title of the thread enumerates four things that contribute to the objective; which is Fastburn:
...combustion chamber size, representing the burntime factor
...burnrate
...squish
...swirl

Rather than it being an adversarial confrontation inferred by the "versus" description, it was more of 'which to choose' or 'do I have to choose' type of thing. We determined that it is neither confrontational nor pick-n-choose. They are all important factors to utilize and hopefully optimize. Used together, the objective is achievable: Fastburn.

For the sake of brevity, I will keep this on the topic of tight squish. Partly because the three other components of fastburn would deserve their own hundred pages or so; partly because two of the other components are affected by the squish effectiveness; and partly because in the 8V redblock, the squish is the one component that was both the most deficient, and the easiest to correct.

To say that another way: the swirl factor is already good in the 8V: the tangential intake runners/bowls/ports are an excellent configuration to promote swirl. The burn time and the burn rate are both affected by the squish effectiveness; both can use improvement; and improving the squish effectiveness will also help shorten burn time and increase burn rate.

As I saw it [and still do], there are two ways to approach the use of tight squish in an engine build:

....the performance/economy/efficiency approach: using the detonation threshhold raising capability of tight squish to maintain--or INcrease--power output....on LOWER octane fuel.

....the performance/haul ass approach....[self-explanatory]: use the detonation threshhold raising capability of tight squish to find out how much power can be made on the same octane fuel as before. OR, find out just how much power can be made on racing grade fuel.

First off, I had to prove to myself whether or not it works.

With the three builds so far, using the performance/economy/efficiency approach, I know that tight squish does work.

My expectations were met and exceeded:
...power output was better, smoother, more seamless from nonboost to boost
...that was accomplished on considerably lower octane fuel
...fuel economy [MPG] was not diminished at all.


that is what I do know.

What I do not know yet:
...how much power can be made on low octane fuel. Because I haven't come close to the limits there yet.

...how much power can be made on high octane pump gas. Because I haven't even started on the performance/haul ass approach.

Why is that? Because I haven't finished my exploration of what tight squish can do. And I have to do that before I can build a fastburn motor.

When I do, I'll let you know.

Thomas Fritz
...the stealth FTi

[Canuckvolvo]

FWIW, I built my B23ET with "snug" squish. Wouldn't exactly call it tight, it came out about 0.043" instead of the ~0.037" I was shooting for. Not sure if it was my measuring, or the machine shop not taking enough off the block (I suspect the former).

Regardless, I have yet to explore the limits of this set-up yet, but so far I can comfortably run 7-8psi of boost on 87 octane. This is on a 2.3litre, ~9.2:1 CR, k-jet motor. On our last cruise (read: 70mph cruising mixed with spirited driving and a couple of sprints over 100) I averaged about 25mpg (US gallons, NOT imperial like the auto mfrs like to use up here).

Any future motors will be built on the same principal. If I haven't thanked you for the advice before Tom (and Kenny, and Matt, and Dale, and...), I'm thanking you now!

[Stereophile33]

athal what head gasket are you running?


Could you swap head gaskets out for thinner compressed head gasket and get closer to your target of .037.......I mean you are .005 from a truly tight squish motor....it could be an option.

[Canuckvolvo]

athal what head gasket are you running?

Could you swap head gaskets out for thinner compressed head gasket and get closer to your target of .037.......I mean you are .005 from a truly tight squish motor....it could be an option.
Standard elring HG ~0.047" compressed IIRC.

For the cost, and potential risk, of going to a custom, or copper (still custom) HG, I don't think it would really be worth it. I'm happy with the results of my snug squish, and definitely of the mind- if it ain't broke, don't fix it! I'm sure with more tuning I could push the limits of 87 octane a bit more, but ask any of the calgary guys- my car is plenty peppy and good on cheap gas as it is. When I swap this motor into the 242 next year I'll see what happens with 94 octane :badboy: I'm sure my tranny will NOT appreciate it :-(