how to work out compression ratios ?

[dr_jekyll]

hi chipmunks,

 

im expanding my horizons beond 2jzs and im trying something on a jaaaag v8 that I believe is abit out of the ordinary. I wont bore you with that but id like to know how I can work out compression ratios as I remove material so I can aim at a desired ratio.

 

the v8 im working on is 8.5-1 and im looking for 9.5-1 but working out how much I have to take off the heads is making my ears bleed.

 

cheers,

craig

[Chris88]

Work out the swept volume (Bore^2 x stroke / 4). If you know that the current CR is 8.5:1 then the swept volume is 7.5 the volume when the piston is at TDC (the residual volume).

 

Divide the swept volume by 7.5 to get the current residual volume and divide the swept volume by 8.5 to get the residual volume for CR of 9.5:1.

 

Subtract the 9.5:1 residual volume from the current residual volume, divide the result by bore^2 and multiply by 4 to give you the amount to skim off the head.

[dr_jekyll]

There that ear blood again lol. Cheers buddy I'll get calculating ... Or go visit my old maths teacher

[absz]

http://www.vwspeedshop.com/Engine%20Calculator.htm

[lewysdanny]

Work out the swept volume (Bore^2 x stroke / 4). If you know that the current CR is 8.5:1 then the swept volume is 7.5 the volume when the piston is at TDC (the residual volume).

 

Divide the swept volume by 7.5 to get the current residual volume and divide the swept volume by 8.5 to get the residual volume for CR of 9.5:1.

 

Subtract the 9.5:1 residual volume from the current residual volume, divide the result by bore^2 and multiply by 4 to give you the amount to skim off the head.

Thought everyone new this !