924Board.org

[friggin]

Hey guys, this summer I'm planning on running a turbo on my 924 NA car.

I'm curious as to how much boost the car will safely hold. I plan on stealing the turbo setup off of an Audi S2. This way I'll have the turbo and intercooler already setup for when I do an AAN swap in the future.

Thanks!
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1979 924 stocker soon to be autocross beast

[fiat22turbo]

The stock clutch slips at around 2-220hp, but don't fixate on specific boost numbers. Start low and work your way up to what the drivetrain can support.

If you improve the cooling system, use a better headgasket and ditch CIS for EFI and electronic boost control you can tune the engine to make more power, safely.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[friggin]

I'm not worried about the drive train holding up haha

I am just curious how much boost the factory engine will hold. I don't want to push 15 pounds at at when it can only hold 6. That's why I'm curious how much it will hold. I don't want to blow it to pieces by pushing to much boost at it.

I am doing a bike carb setup on it this spring and getting rid of the junk CIS.
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1979 924 stocker soon to be autocross beast

[ideola]

'79 US-spec NA motor has 9:1 CR, so that will limit how much boost you can run before detonation, particularly considering the NA combustion chamber and piston design (no quench area to speak of), and the shitty flowing NA head. So realistically, you probably won't be able to run much more than 6psi of boost before inducing detonation. You can offset it a little bit with intercooling, but no amount of charge cooling is going to make up for a combustion chamber, piston, and quench setup that wasn't originally designed for boost.

The two vintage bolt-on turbocharger setups that were made for these cars took slightly different approaches. The BAE setups had an early interpretation of a "conventional" wastegate that was integral to the pressure tube that bled off anything beyond 6psi of boost.

The Windblown system was really unique in that it has a "rotomaster" bleed valve that inversely bleeds off boost as RPMs increase. It came with a tiny turbocharger that produced lots of boost low in the RPM range. As the RPMs increased, the rotomaster bled off progressively more boost, so you would get high boost (~12 psi) at low RPM, and then by 5000 RPM or so would be down to about 4 psi. Not the greatest design for top-end performance, but essentially transforms the streetability of the low compression (8.5:1) early NA cars.
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erstwhile owner of just about every 924 variant ever made

[friggin]

So if I put a 6psi waste gate on the pressure tube I will be fine?

I wish I knew how to post pictures haha. Then I'd show you how I plan on running the bike carbs.[/img]
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1979 924 stocker soon to be autocross beast

[ideola]

I guess it depends on your goals. What are you trying to do? Get a little more pep out of your NA? Or build a max-effort motor? I'm assuming the former...

If it were me, I would do one of two things:
1. (Easier) install a modern turbo with an integral wastegate. Small, compact, proven, effective. Set boost to 6psi
2. (Harder) figure out how to reproduce the rotomaster function with modern components.


I have two each of the BAE and Windblown setups, and I am dying to get one of each of them functioning so I can do comparisons to each other and the factory 931!
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erstwhile owner of just about every 924 variant ever made

[friggin]

I am just trying to get a little more out of the factory NA motor until I can afford to do the AAN swap. I plan on using the turbo off of the s2 so I have that done already to make the swap easier.
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1979 924 stocker soon to be autocross beast

[ideola]

Not familiar with that turbo setup. If it doesn't have an integral wastegate, I would install the wastegate on the exhaust side, not the inlet side (even though the BAE did it that way).

You do realize you'll need to do some serious exhaust fabrication, yes?
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erstwhile owner of just about every 924 variant ever made

[friggin]

Why would you do it on the exhaust side?

Yes I'm aware of the fabrication that would need to be done.
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1979 924 stocker soon to be autocross beast

[ideola]

Short version: long term protection of the hotside. Bleed off pressure in the exhaust track based on an input line from the intake side (just like the OEM setups on the 931/951 etc.).
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erstwhile owner of just about every 924 variant ever made

[morghen]

At 6 psi the car will be quite more fast than what it is now. Depending on fuel, your intercooler efficiency and ofcourse your fine tuning maybe you can run more boost.
One day i'll take a NA, strap a turbo on it and see what boost it can take before it lets go.
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https://www.the924.com

[Cedric]

I know only one who have pushed a stock engine and done it properly. Check this thread:

http://www.924board.org/viewtopic.php?t=38765&sid=ae7784b963848f9d9ba2d86223de3082
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1980 924 Turbo
www.instagram.com/garagecedric/

[JjyKs]

Since we're talking about the boost here.

Does anyone have an idea on how much boost the NA engine could take with E85, Water(/methanol, no idea if it actually helps with e85?) and a semilarge(well almost the largest one that fits in 924 without being outside of the car) intercooler (with intercooler sprayer if the temps seem to get too high)


Most likely gotta reinforce my clutch before actually ramping the pressure over 6psi, but doesn't hurt to actually figuring out the possibilities.

[Rasta Monsta]

Hmm, seems like we used to have a guy on the "absolute bleeding edge of 931 tuning"....wonder why he isn't offering his two cents?
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Cedric]