Hi guys.
Quick question, does anyone know how to work out compression ratios out? Is there a formula i can use?

 

Compression ratio (CR) is all the volume over the piston when the piston is down in the bore (V1) divided by the volume on top of the piston when it's at its top dead center (V2).

CR=V1/V2

Now in V2 you need to count together the volume of the piston bowl (or the dome in negative), the volume the piston comes above the deck height in negative, the volume of the head gasket and the volume of the combustion chamber.

V1 is all the above and the cylinder swept volume.

 

http://mitglied.lycos.de/turbokiller...rh%e4ltnis.xls

 

Thanks guys?
Dont suppose anyone knows the correct compression ratio for a turbo charged 2ltr zetec engine ??

 

Just wondered how much material would need to be removed from the top of a piston the same size as a standard 2ltr zetec piston to run sensible boost on a engine project i am working on?

 

i used a 2,0mm thick decompression plate under a stock
headgasket,gives good 8,2: 1 enough for 12psi and 220hp
on a stock 2,0 Zetec
chris

 

There is no correct compresssion ratio. Depends on the cam timing, turbo, IC etc... For 220hp I wouldn't touch the CR at all.

 

www.fiestaturbo.com

is good information for ZT.

chris

 

Nice one, i will take a look.

 

The Correct CR is higher than a cossie for the same amount of power, due to the thinner bore and longer stroke.