Is it ok to machine piston bowl...

[Andyman]

.....on a forged piston (wossner) for lowering the compression a bit more? (non Clio engine btw)

 

[Michael Woodford MST]

Depends how thick the standard crown thickness is and how much power you want to run through it.

Normally your safe taking a couple of MM off unless your going for silly BHP

 

[Andyman]

I'm ideally looking to run up to 20psi through it max. After machining the CR is in the 9's which is too high and im after 8.5 ideally. Its for a Zetec turbo and its all been measured up with a ST170 gasket the thickest so machining the bowls is the only option for the amount of safe boost

 

[Fred@BTM]

higher CR and more boost!!!

 

[Andyman]

haha i'd rather play safe especially with my luck with cars lol

 

[Fred@BTM]

ah it'll be fine!

 

[Cookson]

higher CR and more boost!!!

Rally spec?

 

[Dan519]

take material from the head, make the chamber a bit bigger.

Usually ok to take a bit from the pistons. Most modern turbo'd engines run a lot higher CR than you'd think though. I'd be happy with 9:1

You can buy supertec pistons that give 8.5:1 on a duratec.

 

[Michael Woodford MST]

I'd be happy with a zetec turbo on 9:1 at 20psi TBH


Cossie boys are up at 9.5:1 and 2.5bar of boost now days

 

[Dan519]

we put together a 200sx engine running 9:1 (higher than standard) a few years ago and made 283bhp at 13psi on a t28. Took it to 16psi with road mapping so dont know a final figure but it was batshit