any one good at maths?

Stoktg · tinkerer Joined: 05 Jan 2002 Posts: 113

Hi, was thinking of putting a turbo on my g200 but im not sure how thick the decomp plate needs to be to bring it down to a reasonable level. Currently my heads are 52.4cc's and engine is 88.5mm bore and 82mm stroke. I think a standard head gasket is 1mm thick/6 cc's, is that correct? Can anyone tell my my current comp ratio and how mich thicker gasket i need to bring it down to around 8:1?
Thanks.

MatMan · tinkerer Joined: 04 Oct 2001 Posts: 280

If you've got the money I'd say get low-comp pistons but if not, then I don't know how thick the plate should be anyway.

Phil · Posted: Fri Jan 11, 2002 3:25 am Post subject: Re: any one good at maths?

It's been posted before but anyway,
(cylinder volume + gasket volume + chamber volume) / (gasket volume + chamber volume)= compression ratio
So for your engine...
cylinder volume=pi*r^2*h
=3.14*42.25^2*82
=504417mm^2
=504.42cc
gasket volume is about 6.15cc
chamber volume you said was 52.4cc
So then.....
comp ratio=(504.42+6.15+52.4)/(6.15+52.4)
=9.62
So your current comp ratio is about 9.62:1
To get it to about 8:1 (I'll just work this one out without wasting screen space) you would need a gasket volume of about 19.66cc which you would get with a gasket about 3.2mm thick.
Phew that took me back a few years to high school maths....
Phil

Phil · Posted: Fri Jan 11, 2002 3:40 am Post subject: Re: any one good at maths?

oops sorry I typed 42.25 instead of 44.25 for the cylinder radius, don't worry but I used 44.25 for the calculations

Stoktg · tinkerer Joined: 05 Jan 2002 Posts: 113

Yeah, thanks for that. I stuffed up on the radius bit, wasn't thinking when i went to work it out and used 88.5 in my calculations and wondering why i had a 2ltr cylinder with a comp ratio of 35:1. What a dumb arse!

Cheers.