Piston Dish cc
Turbo Mini Forums

Hi, im after some recommendations on compression ratios and piston dish sizes.

If the cylinder head i have has 36.0 and 30.0 valves with combustion chambers reshaped to achieve 30cc (med FI head), what piston dish size would you recommend? (1275 +20) and what compression ratio would this give?

(car used for track days, weekend fun, etc assuming metro turbo T3 10 - 15 ish psi MJ is used and intercoller fitted)

cheers, Mark

Edited by MarkGTT on 12th Dec, 2007.

Decide upon your compression ratio, then work backwards to calculate the piston dish required. 30cc is quite a lot in the head so perhaps 10cc would suffice in the piston. This would give you roughly 8.5:1 CR.

acording to my calcs,

with that head (30cc)
that bore (71.65mm)
std stroke (81.33mm)
bk450 headgasket (2.8cc)
and 1cc for ring land and/or volume above the piston

You'll get 8.5:1 with 10cc dishes


beat me to it Tom lol

Edited by Joe C on 12th Dec, 2007.

cheers guys, that gives me a great starting point.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=4377

have a look at this link mark , i,ll fly in the face of popular opinion and say i reckon the gasket volume at 3.95cc average ,my calcs are on the 2nd page ,have a look see what you think might help ,

regards robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I agree.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

ok using 3.8cc for the gasket brings it down to 8.33:1

a 9cc piston will bring it bac to 8.5:1

So is 8:5:1 preferred? a good compromise between lag and boost?

Your engine your choice.

Points to consider-

What are you going to use it for, so what boost level will it run most commonly? If its a pure drag weapon then you will want to use 20psi all the time, hence I'd be aiming for 8:1.

If it is to be used predominantly on the road, then maybe you'll use 10psi all the time, in which case it will be more driveable at 9:1.

cheers Tom, that puts some context to it, and believe i have a better understanding of what i want to aim for.

thanks, Mark.