How to calculate compression
Posted: Wed Dec 20, 2006 8:17 pmIf you don't hate math and don't have a compression tester tool... 
The Calculation of an engine's compression ratio ( C.R. ) is based on the formula :
CR= (SV+CV)/CV
SV= Swept Volume for one cylinder in CC's= Bore x Bore x stroke x 12.9
CV= Clearence Volume for one cylinder in CC's= HV minus EDV plus DV plus GV
HV= Head Volume (measured in CC's)= Best if measured because head volume vaires
EDV= Effective Dome Volume (measured in CC's)= Dome volume minus valve relief and/or dish volume
DV= Deck Volume clearance (piston to deck) (measured in CC's) = Bore x Bore x Deck Height x 12.9
GV= Gasket Volume (measured in CC's)= Gasket Bore x Gasket Bore x Compression Thickness x (12.9 or enter known gasket volume)
edit: Cubic Inch Displacement measurement
Bore x Bore x stroke x .7854 x 4(cylinders)
The Calculation of an engine's compression ratio ( C.R. ) is based on the formula :
CR= (SV+CV)/CV
SV= Swept Volume for one cylinder in CC's= Bore x Bore x stroke x 12.9
CV= Clearence Volume for one cylinder in CC's= HV minus EDV plus DV plus GV
HV= Head Volume (measured in CC's)= Best if measured because head volume vaires
EDV= Effective Dome Volume (measured in CC's)= Dome volume minus valve relief and/or dish volume
DV= Deck Volume clearance (piston to deck) (measured in CC's) = Bore x Bore x Deck Height x 12.9
GV= Gasket Volume (measured in CC's)= Gasket Bore x Gasket Bore x Compression Thickness x (12.9 or enter known gasket volume)
edit: Cubic Inch Displacement measurement
Bore x Bore x stroke x .7854 x 4(cylinders)
They haven't taught us that in college!