924Board.org

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Hey everybody. I just bought a 1981 924 Turbo and I'm rebuilding it. The motor already had a broken Timing Belt so the head is out being working on right now. The questions that I have is I'm looking for a performance exhaust system, a high-flow radiator and an intercooler for my 931. Does anybody have any sugestions? Do the 944 Turbo exhaust system fit the 931's? How about the radiator? Any help would be appreciated.
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1981 924 Turbo

[Rasta Monsta]

I like my Ron Davis rad. The 931 exhaust flows pretty well. . .but if you want it louder I believe a 944 aftermarket muffler will work.

As for intercoolers, please use the SEARCH function. There have been many different successful installs by members here.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[ideola]

The cat-back is the same for the 931 and the 2.5L NA motors (924S & 944). The 931 exhaust is already 3" so not sure what you expect to gain, other than a cat-delete or a freer flowing muffler. As for cat-delete, the cat section is unique to the 931, and I don't believe there are any aftermarket alternatives, so you'd have to have something custom made.

Regarding intercoolers and other performance mods, here is a good thread to start with: http://www.924board.org/viewtopic.php?t=25795

An alternative to the radiator is to go with a 924S/944 rad, or better yet, a 951 rad. While not directly swap in, they should fit the profile and should be fairly easy to adapt with a little creative bracket fabrication. The other thing to consider is replacing the somewhat anemic OEM fan with a lower profile, higher efficiency fan setup such as a Spal or Davies-Craig unit, along with a properly designed shroud. The OEM shroud is probably not the best design possible.
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erstwhile owner of just about every 924 variant ever made

[9xx]

[flosho]

Yeah, I'll be the first to tell that the 931 and 924S/944 use different flanges from behind the catalytic converter.

If you want a cat-back exhaust look at 944 Turbo options.


Additionally the stock exhaust is 2.5".
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[This Space For Rent]

[ideola]

Sorry about that! 951 cat-back it is, not 924S/944.
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erstwhile owner of just about every 924 variant ever made

[gegge]

The 931 exhaust is 60mm OD which makes a 2,5" an easy upgrade since it is slip-on.
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

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So let me get this correct, the 944 Turbo (951) cat-back system will bolt on to my 924 Turbo (931)? I found a cat-back system that will give me around 26 hp.

Also where can I get a 1.0 bar waste-gate spring?

There's so much info here it's hard to find everything. I could spend days on here but my work wouldn't like that very much.
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1981 924 Turbo

[morghen]

[Rasta Monsta]

[Joes924Racer]

yea why did u pick that # thats insane. & not possible.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

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Ok it's not a cat-back it's a full system, sorry about the mis-type. But the system is from Fabspeed, it's for a 944 Turbo but here's the link http://www.fabspeed.com/944Turbo.html I'm going by what they are saying.
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1981 924 Turbo

[gegge]

Bypassing a 25 year old catalytic converter could be the reason for the hp gain. . A tuned 951 will gain from a full 3" but a 2,5" system should be adequate for 931 powerlevels
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[Rasta Monsta]

Yeah, that 26 HP sounds like about 10% of stock 951 output. So, if the 10% is correct (debatable) you are looking at 15 HP on a stock US 931.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Khal]