Compression Test

Compression Tests should be performed on a warm engine, with the fuel pump fuse/relay unplugged (and the fuel rail drained/depressurized), and the throttle should be held fully open while testing. These pressure values will be less at higher elevations, and can be lower on engines with more mileage. Aggressive cams or cam timing will also reduce the measured cylinder pressure during a compression test, but should still give consistent readings. You should not have more than 10% variance between cylinders.
Typical compression test results should be approximately 150-170 psi per cylinder for ~8.5:1 CR, 210-250 psi per cylinder for ~10.5:1 CR.