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Intro and Project Smurf

MCHN8

Member
Joined
Mar 7, 2019
The Smurf: 84 245, LC9, G42-1200C, 8.8

Greetings everyone!

First post here in what will hopefully be a relatively quick project. Many thanks for the wealth of information in this group.

It's a familiar story: A lovely 245 meets a handsome 5.3 and the pressure gets turned up. She's not getting any younger. He's only a catch for a few more years, and so it goes.

So far we have a roller, an 8.8, and cleaned up block. I'll do my best to document things here.

Pics or it never happened:

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Nice wagon. Always loved that color! The tribes of palos verdes, did you buy this volvo 240 from them, Lol

Cheers! Didn't know about that movie, but yes. I think the answer is yes. :omg:

oh how i wish that was true

The perks of being married! Invisible is good. Nothing to see here.

The scavenger hunt has been in full effect. We stumbled across a Bertickup in Morgan Hill and Volvo yogi in Boise. Good times, and found some much needed parts for the new interior, gauges, cosmetics, and various fasteners. Pretty stoked on these:

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NOS Tach!

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That was in Boise. A cool Father/Son hobby yard. Not sure if they're on the forum.

That yard looked familiar- I know someone who has a youtube channel who visited and toured the place (I believe he's a member). IIRC the owner has a really awesome 142GT?
 
It was great meet crew at Davis. Cool crowd, a friendly and sharing bunch, and definitely a day of inspiration and ideas. Many thanks!

Slowly but surely this project is getting traction. The short block is done and built to handle way more than I intend to push through it.

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Also found a decent 8.8 and have it cleaned up. The goal with the rear is to copy the coilover conversion some of the guys have been doing. I'm tempted by watts link and may go that route eventually but a panhard bar will be fine for now.

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Kinda funny, someone signed the smeg under the car back in 95 :)

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Your 5.3 and 8.8 are both looking great. Nice progress so far!

Turbo wise, I'm thinking that a GTX4088R or GTX4294R will be perfect for your goals with this car. Talking within the Garrett catalog of course - if you go elsewhere I'm not offended. I'm not sure if you spoke with Erik (cosbysweater) at Davis but he is running a GTX4202R on his blue sedan, and seems to love it so far. Both of the GTX42 variations share the same turbine wheel and can use any of the 4 turbine housing A/Rs available. The difference is on the compressor side; 94mm exducer vs. 102mm exducer (shortened to "02" in the name). Your power requirements are a bit lower meaning that the smaller compressor is probably a better match.

The 4088 is smaller on both compressor and turbine ends, and also runs a smaller 10mm ball bearing system so the whole unit is more compact. I'll have to dig a bit deeper into some simulation work to give you a definitive answer on which would be better between the 4088 and 4294, but at this point I'm pretty sure either would work well.
 
Cheers Chris! As you know I will defer to your turbo recommendation any day.

I lurked and snooped around Erik's car but did not get to meet the man. Definitely impressive! If I understand correctly he is putting down near 1k whp? That would be well above my goals given that my car will be a "family cruiser". ;-) Plan A is to keep it around 650 - 700 whp with as early a spool as possible.

Assuming we go with the 88, roughly what range of potential output would you expect? The car will be set up for E85.
 
Cheers Chris! As you know I will defer to your turbo recommendation any day.

I lurked and snooped around Erik's car but did not get to meet the man. Definitely impressive! If I understand correctly he is putting down near 1k whp? That would be well above my goals given that my car will be a "family cruiser". ;-) Plan A is to keep it around 650 - 700 whp with as early a spool as possible.

Assuming we go with the 88, roughly what range of potential output would you expect? The car will be set up for E85.

Hey Nate - I'm not sure of Erik's exact power lately...paging Cosbysweater...

Regarding the GTX4088R, with a well-flowing intake system and running E85 I think it should be capable of around 900hp at the flywheel, as an educated guess.

Looking at your power targets I'm going to call 700whp ~ 825bhp (at the flywheel) before driveline losses.

For E85 at that power output it looks like mass airflow would be around 70 lb/min at 6500 rpm. Using a conservative estimate of engine VE and BSFC I'd expect pressure ratio of 2.2. With ~95% VE you'd be around 1.95 pressure ratio (lower boost to make the same power).

Plotting these points on the GTX4088R compressor map puts you to the right of center, and maybe low 70% range for compressor efficiency. That's at peak power however. For nice driveability in a road car it's OK to sacrifice a bit there in order to bias peak performance in the engine midrange. In this case I think you'd hit peak compressor efficiency around 5000 rpm at full load. It looks like a nice match.

I haven't had the chance to do a full simulation yet, so none of this takes the turbine into account, and therefore I'm not able to predict your boost threshold rpm ("spool point") yet but I can say that a 4088 should be more responsive in transient conditions (throttle and load changes) vs. a 4294, all else being equal.
 
For E85 at that power output it looks like mass airflow would be around 70 lb/min at 6500 rpm. Using a conservative estimate of engine VE and BSFC I'd expect pressure ratio of 2.2. With ~95% VE you'd be around 1.95 pressure ratio (lower boost to make the same power).

Plotting these points on the GTX4088R compressor map puts you to the right of center, and maybe low 70% range for compressor efficiency. That's at peak power however. For nice driveability in a road car it's OK to sacrifice a bit there in order to bias peak performance in the engine midrange. In this case I think you'd hit peak compressor efficiency around 5000 rpm at full load. It looks like a nice match.

I haven't had the chance to do a full simulation yet, so none of this takes the turbine into account, and therefore I'm not able to predict your boost threshold rpm ("spool point") yet but I can say that a 4088 should be more responsive in transient conditions (throttle and load changes) vs. a 4294, all else being equal.

Oh great turbo whisperer!

If I understand correctly we would be on the edge of the %70 efficiency island and thus have the higher efficiency area at lower flow rates aka regions "normal" drivers are in "most" of the time. It looks like surge won't be an issue but we may get closer to choking the turbo?

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Is that your 61 olds? Seen it on cl a few times.

I wish, it's a beauty!
 
If I understand correctly we would be on the edge of the %70 efficiency island and thus have the higher efficiency area at lower flow rates aka regions "normal" drivers are in "most" of the time.

Yes, exactly!

It looks like surge won't be an issue but we may get closer to choking the turbo?

A little closer than you'd be with a 4294. Garrett defines the "choke line" at 58% efficiency, but full-on choke (where the flow goes sonic) won't happen until efficiency has dropped quite a bit more and may be closer to 90 lb/min for the 4088. It won't physically choke at lower pressure ratios but at 2.2 it probably would. The physical choked flow boundary is not shown on the map due to that 58% standard cutoff though. The speedlines go towards asymptotic vertically and stack up on each other.

In the real world if you had a fully instrumented turbo and reached physical choke conditions, you'd see turbo speed increase exponentially for little to no change in boost pressure. This is what happens with an inlet restrictor upstream of the turbo, as used in WRC and other rally series and some road racing, but that choke boundary is moved left quite a bit and truncates the map significantly...assuming the restrictor diameter is smaller than the housing inducer diameter.
 
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