Engine Compresion Ratio Formulas

[simplegreen]

written by:ace1875 Honda-Tech Member
from:honda-tech.com

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)