Convert compression ratio to PSI (pounds per square inch).
Engine Specs
Static CR (e.g. 10.5)
Height above sea level
Results Title
Psi Value246.6 PSITheoretical max at TDC
Atm Pressure14.70 PSILocal air pressure
Cranking Pressure
Cranking pressure is always lower than this theoretical value because the intake valve stays open slightly into the compression stroke.
Overview
Compression testing measures cylinder pressure in PSI. Converting between compression ratio and PSI helps diagnose engine health. Low compression indicates worn rings, valves, or head gasket issues.
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Pro Tips
Higher altitude results in lower compression PSI due to thinner air.
A 'leak down' test is more accurate than a compression test for diagnosing engine health.
Fun Fact
Did you know? Diesel engines can have cranking pressures well over 400 PSI because of their high 20+:1 compression ratios!
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Fun Facts
Formula: PSI ≈ Compression Ratio × Atmospheric Pressure (14.7 psi at sea level)
