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B230 compound/sequential turbos

A question what is the smallest oem turbo with twin scroll.


It's needs to be twin scroll because i what to do a built in quick spool valve so it spool even faster same with the big turbo. Borg Warner have done something like this in a prototype.

Something like this. Not my picture.

ADegWMUl.jpg

you would probably want to look at the diesel world for small twin scroll stuff. hx35 is fairly small (not dimensionally though!). you can probably get a twin scroll housing for the big turbo you already have, and work from there.
 
Update!

Needed to make a oil return in to the oil pan because the big turbo sits to low to make it to the stock oil return.
LQnVASVl.jpg

Just to make sure, the tube going to oil pan is steel, going in a bit of an angle, and is still above the oil line, right? From the camera angle it is hard for me to see. :oops:
 
I have look at maybe using a vnt turbo for a diesel for the small turbo. Something lika a gt15 or gt17 turbo.


Some inspiration from bmw with there 3 and 4 turbo 6 cylinder engine.

J3f9hGyl.jpg


bAC4YMDl.jpg
 
Plenty of OEM turbos these days are twin scroll. First one that comes to find is the BMW N55 single turbos, but that's because I've got one saved for a future project.

From a quick Google looks like Mini (so FWD BMW) is teasing twin scrolls now, and if you've ever held one of those turbos you know just how Mini it is
 
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Plenty of OEM turbos these days are twin scroll. First one that comes to find is the BMW N55 single turbos, but that's because I've got one saved for a future project.

What are you going to do about its exhaust manifold? Is it part of the turbine or you can separate them?
 
H?lsningsfraser Marcus,

Where are you in your work? Done anything else yet?


TIA
Hubert

I bit on the wiring harness but not much had a lot at work so not a lot of spare time right now but it's getting there.

Have also looked around at smaller turbos then the 16t so i can get almost instant boost
Like a gt1549v that is a vnt turbo so hope it doesn't melt :-D or a turbo from a mini like James M suggested. I get to test when the head gasket blows with so much boost at so low of a rpm.
 
Small update!

Everything on the intake side is done now! And only the exhaust left on the hot side.

The engine harness is done to and i only need to hook in up to the car.

wasXD5ql.jpg


Zc8GHvUl.jpg
 
Small update!

Everything on the intake side is done now! And only the exhaust left on the hot side.

The engine harness is done to and i only need to hook in up to the car.

Too bad Hubert isn't here to see this.

Great progress!

Forgive me if this was already answered, but are you putting this on a stock B230FT? I'm guessing over in Sweden you guys have reasonable quality fuels to combat knock.
 
Too bad Hubert isn't here to see this.

Great progress!

Forgive me if this was already answered, but are you putting this on a stock B230FT? I'm guessing over in Sweden you guys have reasonable quality fuels to combat knock.

B230ft with forge connecting rods and stock f pistons so a compression ratio of 9.7:1. Running on E85 right now so not worried about knocking, But it's flex fuel.
 
Marcus - big kudos to you for building this and trying it out.

It looks like you are building what we refer to in the turbo engineering world as a "series sequential" system. By implementing the turbine bypass valve between the two turbine stages, you are allowing the larger low pressure (LP) turbo to be shut off at low loads and low engine speeds, and allowing the smaller high pressure (HP) turbo to operate on its own. Once there's enough exhaust energy to power the larger LP turbo then you open the valve and allow both the turbines and compressors to operate in series, giving you higher boost than would be possible from either turbo individually.

If instead you wish to completely switch between the LP and HP stages at some point in engine operation, then you are talking about a pure sequential system, i.e. the two turbos are operating in timed sequence, one after the other, but never one into the other - never in series.

Can you clarify which type of system you're going for here? Or maybe planning for either possibility?

A few thoughts after looking at your system photos:

  • If you open the wastegate which vents to atmosphere after the HP turbine, then you may be essentially shutting down the LP turbo completely (depends on flow capacity of LP turbine and of the wastegate).
  • If you open both the atmospheric wastegate and the inter-stage wastegate, then you are bypassing both turbine stages.
  • If you want to run this as a series-sequential system (first type described above) then you will want a compressor bypass valve between the HP and LP stages. This can be a passive spring loaded flapper valve, but it's needed because without it, when your turbine bypass valve is open and you want the LP to run on its own, then the LP compressor will by trying to force-feed the HP compressor which won't be actively working, so it will effectively just be a restriction. Adding a compressor bypass valve would let the LP boost pressure dump directly into the intercooler and on to the engine. This valve would need to be about the size of your charge plumbing between the LP compressor and intercooler, not any smaller.
  • Again if you want to run in series, an inter-stage cooler between the two compressors is an absolute must-have in my opinion. Without it you will likely overheat the HP compressor and kill efficiency, because the air coming into it will already be quite hot after being compressed by the LP compressor.


In general terms, the reason the large compressor feeds into the smaller one is a function of how radial compressors work. They just multiply the inlet pressure via pressure ratio to get to an outlet pressure. They really don't care what the value of the inlet pressure is... whether it's atmospheric or already boosted (by the LP stage) doesn't matter much because the air flow correction accounts for that. If you look at a compressor map, the flow axis is always corrected flow, not actual physical flow. At atmospheric conditions these are essentially the same. But when you pre-compress the inlet air with another turbo, the corrected flow rate actually goes down, meaning a smaller compressor is a better match for this already-boosted airflow. If you swapped the two turbos around then they would both be very poorly matched for the conditions they would see, and performance would be terrible. The smaller turbo would also then act as an inlet restriction which would severely limit your total power and negate the reason for using a larger LP turbo in the first place.
 
Marcus - big kudos to you for building this and trying it out.

It looks like you are building what we refer to in the turbo engineering world as a "series sequential" system. By implementing the turbine bypass valve between the two turbine stages, you are allowing the larger low pressure (LP) turbo to be shut off at low loads and low engine speeds, and allowing the smaller high pressure (HP) turbo to operate on its own. Once there's enough exhaust energy to power the larger LP turbo then you open the valve and allow both the turbines and compressors to operate in series, giving you higher boost than would be possible from either turbo individually.

If instead you wish to completely switch between the LP and HP stages at some point in engine operation, then you are talking about a pure sequential system, i.e. the two turbos are operating in timed sequence, one after the other, but never one into the other - never in series.

Can you clarify which type of system you're going for here? Or maybe planning for either possibility?

A few thoughts after looking at your system photos:

  • If you open the wastegate which vents to atmosphere after the HP turbine, then you may be essentially shutting down the LP turbo completely (depends on flow capacity of LP turbine and of the wastegate).
  • If you open both the atmospheric wastegate and the inter-stage wastegate, then you are bypassing both turbine stages.
  • If you want to run this as a series-sequential system (first type described above) then you will want a compressor bypass valve between the HP and LP stages. This can be a passive spring loaded flapper valve, but it's needed because without it, when your turbine bypass valve is open and you want the LP to run on its own, then the LP compressor will by trying to force-feed the HP compressor which won't be actively working, so it will effectively just be a restriction. Adding a compressor bypass valve would let the LP boost pressure dump directly into the intercooler and on to the engine. This valve would need to be about the size of your charge plumbing between the LP compressor and intercooler, not any smaller.
  • Again if you want to run in series, an inter-stage cooler between the two compressors is an absolute must-have in my opinion. Without it you will likely overheat the HP compressor and kill efficiency, because the air coming into it will already be quite hot after being compressed by the LP compressor.
In general terms, the reason the large compressor feeds into the smaller one is a function of how radial compressors work. They just multiply the inlet pressure via pressure ratio to get to an outlet pressure. They really don't care what the value of the inlet pressure is... whether it's atmospheric or already boosted (by the LP stage) doesn't matter much because the air flow correction accounts for that. If you look at a compressor map, the flow axis is always corrected flow, not actual physical flow. At atmospheric conditions these are essentially the same. But when you pre-compress the inlet air with another turbo, the corrected flow rate actually goes down, meaning a smaller compressor is a better match for this already-boosted airflow. If you swapped the two turbos around then they would both be very poorly matched for the conditions they would see, and performance would be terrible. The smaller turbo would also then act as an inlet restriction which would severely limit your total power and negate the reason for using a larger LP turbo in the first place.


Right now it setup like a compound system just to test it out. After that I will build a bypass valve so i can get a bit of compunding at low rpm then when the LP turbo produce the same boost as the compunded boost pressure the bypass valve will be fully open.

So when the HP turbo produces 14.5 psi the LP turbo at 0 psi so the valve will be fully
closed. So when the boost of the LP turbo start to increase the valve will start to open depending of how i program it. So the longer i keep the valve closed the more compund boost i willl get.

all of the exhaust gases from the HP turbo through the LP turbo even the wastegate. So I can switch of the HP turbo with the wastegate in between the turbos, But the LP turbo will always produce boost, I don't think the wategate for the LP turbo is big enough to bypass all of the exhaust so there will always a little of boost. But yes I can essentially shut the turbos off.

There will be a inter-stage intercooler later on.

Insted if a bypass valve that is activated by a spring i'm thinking of using a throttle body controled by the megasuirt so i can control at which boost level it's should open at. (More boost on E85 then gas).
 
Right now it setup like a compound system just to test it out. After that I will build a bypass valve so i can get a bit of compunding at low rpm then when the LP turbo produce the same boost as the compunded boost pressure the bypass valve will be fully open.

So when the HP turbo produces 14.5 psi the LP turbo at 0 psi so the valve will be fully
closed. So when the boost of the LP turbo start to increase the valve will start to open depending of how i program it. So the longer i keep the valve closed the more compund boost i willl get.

all of the exhaust gases from the HP turbo through the LP turbo even the wastegate. So I can switch of the HP turbo with the wastegate in between the turbos, But the LP turbo will always produce boost, I don't think the wategate for the LP turbo is big enough to bypass all of the exhaust so there will always a little of boost. But yes I can essentially shut the turbos off.

Interesting ideas. Please share your testing results here. I've not seen a series system managed this way, and curious to see what you can get out of it.

There will be a inter-stage intercooler later on.

Good to hear. You should see big gains after adding the interstage cooler. Pre-turbine exhaust backpressure on the HP side will be reduced because the HP compressor won't have to work as hard to reach your final desired "compounded" boost pressure.

Insted if a bypass valve that is activated by a spring i'm thinking of using a throttle body controled by the megasuirt so i can control at which boost level it's should open at. (More boost on E85 then gas).

That sounds pretty reasonable. A throttle body should work pretty well as a compressor bypass valve, and you would get the benefit of active control too. I'm betting that you will end up opening it whenever the HP outlet pressure is higher than the LP outlet pressure, and keeping it closed whenever the LP is higher than HP.

Not sure if or why you would want to allow it to be open if LP > HP, because then you're just adding unnecessary volume and restriction into the charge plumbing by allowing boost to travel through the "coasting" HP stage.
 
Update!

Got the harness in and plug in and got the engine running:)

No water in the engine so short running so it doesn't overheat. ignore the afr reading the sensor is not in the exhaust because there no exhaust.

Got some sync problems so I will add a 10k shunt resistor between the vr+ and vr-

<iframe width="560" height="315" src="https://www.youtube.com/embed/o4f7JX_8A7Y" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
Update!!

went for a test drive!!

All went well first a thought but only the small turbo was working good, The big turbo was only producing a little bit of boost. Weird I thought but okay and kept going then a really went for it and poof when a let of the throttle, and no boost almost weird so I limp it home and took it apart and well the LP turbo as seen some better days:oops:. The HP turbo took some damage to but not a lot.

bcwhSJhl.jpg



CorkxRel.jpg


VrPVXVLl.jpg


The piece that I think did all the damage is that "small" piece of metal beside the compressor wheel.

I'm thinking of buying a china GT3076 turbo for testing so I don't break a expansive turbo.
 
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Running again and making boost. On spring pressure is 0.5 bar (7 psi) on both turbos so I got around 0.8 bar (11 psi) boost together. Then I turned the boost up on the small turbo to 0.8 bar (11 psi) so total boost is 1.6 bar (23 psi):cool:. I'm aiming for 1.5 bar (21 psi) on gas and more than 2 bar (29 psi) on e85.

New vs old turbo.
tBLEA8xl.jpg


New turbo vs 33cl (12 oz) can
B59OlJPl.jpg

Data log snapshot. Lean AFR so need to add fuel.
Xij02ril.png


Now the fun begins all the tuning so it will work better and better and all the boost:cool:
 
marcusj2001 ive been lurking your thread since the beginning and i really enjoy your project and the updates thank you for all of it
 
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