Cp 9:1 Pistons With 10mm Lift And 1mm Os Valves?

[R32 TT]

Hey gang,

Lucky me has my engine apart and am looking to put in some of the so called "9:1" CP Pistons in.

Brad from Spool been helpful and let me know that the pin height is 32.5mm and the dome of the piston is 6mm.

So assuming a 0 deck height:

Combustion Chamber (guessing at this point) is roughly ~64cc

So with a 1.0mm (87mm) head gasket, 86.5mm bore, stroke of 86mm etc - this gives 8.90:1 compression I believe.

A 1.2mm head gasket would give about 8.75:1 - but the clearance in the squish area might be getting a little large then (just my opinion, feel free to correct me on this)

A couple of questions for those of you that have done this. Has anyone used this combo and managed to squeeze 1mm oversize valves in and run cams with 10.0mm lift?

Also, with this compression - what sort of boost would you guys consider safe on 98 pump fuel?

Cars purpose is mainly a club/track car with occasional street drive. Would like to see 450-500rwhp on say 1.5 bar max.

8.9:1 ok for this?

The previous build looks to be have been running only about 8.0:1 and made 460rwhp... I am hoping this new setup will provide better throttle response and more torque - don't care if it doesn't make any more horsepower - what I had was good..

Any words of wisdom would be great.

[N1GTR]

1.5 bar means a lot more from a to4z compared to a set of stockers, so knowing the turbo will help

best person to speak to in Australia about this (other than your engine builder/machinist) is steve from quantum racing

[N1GTR]

...also yes that CR will be fine

[R32 TT]

...also yes that CR will be fine

Oops! Thanks Steve forgot to mention that I am running twin low mount Garrett -5's. (2860r's)

But I am a little confused.. why did you say the turbo makes a difference and then tell me the CR will be fine?

Edited February 22, 2010 by R32 TT

[N1GTR]

Sorry, turbo makes a difference for the power you quoted, that's all

being a car that will see corners, the increased CR will be nice and usefull

Also there's plenty of guys running that boost (and more) with similar CR's, don't be stressed, it sounds like a great setup.

I don't know about the valves though, nice to have to be different, but if you havnt bought them already I'd suggest saving the money as many many guys have prooved stock valves are fine for that power (and more)

[R32 TT]

Sorry, turbo makes a difference for the power you quoted, that's all

being a car that will see corners, the increased CR will be nice and usefull

Also there's plenty of guys running that boost (and more) with similar CR's, don't be stressed, it sounds like a great setup.

I don't know about the valves though, nice to have to be different, but if you havnt bought them already I'd suggest saving the money as many many guys have prooved stock valves are fine for that power (and more)

Excellent, thats good to know - I'm looking forward to feeling the difference!

The oversize valves thing is simply because I need to re-do the head from ground up anyway.. so I figured the cost of buying and fitting 1mm oversize valves would be not much different to fitting stock size... so it more because I have the opportunity to do it now. Hopefully it will be a useful gain..