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Home > Help Needed / General Tech Chat > 998 Turbo setup


17 Posts
Member #: 11707


Been some time since i posted on here but building a 998 turbo and after any tips on best setup. The engine is a collection of bits that were laying around and spares for another engine. So its a little bit messy before i even start. I will detail the spec -

998 + 20 pocketed and decked
Standard Hepolite flat top pistons
12G940 Head - Ported - Chambers opened up - 30mm exhaust stainless - 36mm inlet Rimflow
Standard crank
Standard con rods
All new bearings
Mini spares evo 001 cam
Standard duplex kit with IWIS chain
New standard followers
Standard rocker set - new shaft, springs
Adjustable pushrods
Standard Turbo clutch with green diaphragm
slightly lightened standard flywheel
HIF44 turbo carb
Standard Metro turbo inlet
standard metro turbo exhaust manifold
Choice of T2 or T3 [bulkhead box will be fitted]
Gearbox will be standard except central oil pickup and uprated diff pin

As I say this is an odd build using what I have already with some nice new bits as required. Its a low budget build. I wouldnt be expecting huge power from it.

Also will be using 65DM4 distributor and NO intercooler.

What is the highest CR anyone has used on a 998 Turbo? Im thinking of running slightly higher CR and lower boost. Im considering 9.4 CR

Any comments welcome


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287 Posts
Member #: 10128
Senior Member


Some talk of CR for 998 on here:

As Mike mentions MG Metro Turbo was 9.4:1, no intercooler, but mild boost.

I'll let someone cleverer than I review the selection of engine components.


17 Posts
Member #: 11707

Thanks for the response and the link. Read loads on here about different options but haven't found much regarding the higher CR option that has been tried and tested. If i start at 9.4 I can always bring it down if needed.


10 Posts
Member #: 11947

That all sounds very familiar to the engine I will be building but I have some dished +20 pistons to get the CR down.
I have been recommended the mini spares x pin diff as being well up to the power (my goal being 100 bananas) not heard much about the uprated pin??

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