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[MillsMotorsport]

Hello,

This is my first post on this forum and I'd like some help from the turbo gurus out there on a turbo repair/upgrade for the 932 (with Carrera GT body kit) I've just bought here in Melbourne, Australia. It has a dead turbo (something metal was left in the inlet hose and went down the inlet and "massaged" the compressor wheel ''). In fact it has a dead 931 CGT spec turbo I believe. It also came with spare stock 931 Turbo.

It has a recently freshened engine that is currently out of the car, awaiting the turbo repair/replacement.

The numbers are (engraved, not stamped on the turbo name plate), CGT Spec Turbo:
K26.86.8
80.518.0240
5326.970.6023

For the stock turbo (stamped) which is actually a 1981 USA 931 Turbo:
K26-2660GA4.10
83 107 0577
5326 970 6022

I'd like some help/advice in what to do with it........

I'm going to make a custom water to air charge air cooler (intercooler) that fits where the CGT air to air would normally fit (straddling the rocker cover) as I think controlling the charge air temp is critical to performance and engine longevity. It's currently just at the very early design stages, but hoping we can come up with something that will handle up to 300 flywheel hp (maybe 350 hp if we can make it fit).

So, onto the turbo options:
1. Rebuild CGT spec turbo (replace damaged compressor wheel like for like) with no modifications and install.

2. Rebuild CGT turbo and replace damaged compressor wheel with:

[Raceboy]

You can't just slap GT3071 onto 931 without modifying fuel system and ignition. It would be waste to use GT30 with CIS anyway and I would go EFI anytime. This way you will have at least some longevity of the engine.
If you are planning to get more power, START with efi and only then upgrade the turbo. Otherwise you will probably have to rebuild the engine meanwhile also.

If you are on the budget, stick with stock 931 turbo, it is not worse turbo than CGT one and IIRC it actually has slightly larger turbine housing which helps to lower EGT's. 951 220hp turbo is better than any 931/CGT turbo regarding compressor. You would have to install separate bypass valve as 951 unit doesn't have one like 931 compressor housing does.

IMHO, I would go just with air-air intercooler. Buy 951 unit and with some work (a lot less than fabricating a WORKING air-water ic) it is a very good solution.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[gegge]

The CGT is a standard 2660 turbo with a larger turbinehousing(#6 vs. #4). Just swap that if you are looking for +200hp and you got yourself a "new" CGT turbo. I havn´t seen the compressor map but don´t think it is wise to push it beyond 200whp. The early 951 turbo doesn´t fit because the turbinewheel is smaller i diameter than late 951 and 931. Except from the recircvalve it is an easy upgrade good for 300hp. A larger K27 is only recommended at +300hp.

The CGT/S2 CIS can handle 250-260hp with good stock injectors, maybe even more. Just make sure the AFR is on target! I belive that it is good for 300hp if you got the possibility to adjust the fuelpressures.

Next problem to solve; I would be careful running cast pistons without a good tune and an effective intercooler.

A nice setup would be using the 5326-123-2038 GTS compressorwheel in stock compressorhousing. Or 5326-123-2022 from the late 951.
_________________
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

[MillsMotorsport]

So if I use the CGT turbine and turbine housing, with the stock compressor housing (if the CGT housing is damaged, then I'll just use the stock US model compressor housing) and get the turbo guys to replace the damaged compressor wheel with one of the P/N's that you've listed

[MillsMotorsport]

Hi, I've bought a K27 compressor housing, back plate and compressor wheel from a 911 (964) Turbo. The plan is to get my turbo guy to bolt this "cold side" onto the 931 turbine.

The BW part number for the complete 964 Turbo is: 5327 988 7200
The Porsche part number is: 930.123.013.04

The BW web site says this turbo was good for 235kW or 320HP in stock form on the 964.

I'm interested in what I'll end up with once the two "halves" are bolted together. Has anyone done this hybrid before?

I have taken Raceboy's advice and I am currently rebuilding the bottom end with forged pistons and ARP hardware, I have a 951 FMIC (yet to be fitted) and am planing EFI (probably Link G4 Storm ECU - from NZ). Will keep stock manifolds and a reconditioned, but basically stock cyl head (for the time being).

[WEASEL149]