9:1 cp pistons

[-S Double C-]

220PSI = 15:1 compression. How do you get that from a 10:1 compression motor? Heat is the only factor I can think of that can affect pressure so drastically.

tha hell you talking about my old 10:1 gsr motor had 240 all across the board and my 10:8:1 h22 had 270

[Atlblkz06]

tha hell you talking about my old 10:1 gsr motor had 240 all across the board and my 10:8:1 h22 had 270

At 10.8 CR, 10.8 x 14.7 = 160psi. Why is the cylinder pressure 270?
270psi/14.7 = 18 times normal air pressure but the CR is only 10.8

CR should be a good way of estimating cylinder pressure but from your examples, obviously it isn't. What am I missing?