This is my example. A compression ratio of 10:1. Does this mean that when the piston is at top dead center, the pressure in the gap between the top of the piston and the top of the head is 10 times the atmospheric pressure? Or does it mean that the pressure is 10 times greater than Fuel/Air mix when the piston is at bottom dead center just after inlet, and before compression? This has been bugging me. I imagine that the higher the compression ratio, the greater the power you get out of your motor, until you compress it so much that it won't explode at all. Anyone!?!