What does a compression ratio mean?
Compression ratio is a way to describe how much the unburned fuel/air mixture is “squeezed” before it is burned. Visualize one cylinder in a motor with the piston at Bottom Dead Center. The volume above the piston crown is the volume of the cylinder plus the volume of the combusion chamber. Call that number A. Now visualize the same cylinder with the piston at Top Dead Center. The volume above the piston crown is the volume of the combustion chamber. Call that number B. The compression ratio is A divided by B.
