<P> Measuring the compression pressure of an engine, with a pressure gauge connected to the spark plug opening, gives an indication of the engine's state and quality . There is, however, no formula to calculate compression ratio based on cylinder pressure . </P> <P> If the nominal compression ratio of an engine is given, the pre-ignition cylinder pressure can be estimated using the following relationship: </P> <Dl> <Dd> p = p 0 × CR γ (\ displaystyle p = p_ (0) \ times (\ text (CR)) ^ (\ gamma)) </Dd> </Dl> <Dd> p = p 0 × CR γ (\ displaystyle p = p_ (0) \ times (\ text (CR)) ^ (\ gamma)) </Dd>

Pressure at the end of compression in diesel engine