Pre-ignition cylinder pressure of an engine

Description

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. If the nominal compression ratio of an engine is given, the pre-ignition cylinder pressure can be estimated by the cylinder pressure at bottom dead center, the compression ratio and the specific heat ratio for the working fluid, specific heat ratio for the working fluid, which is about 1.4 for air, and 1.3 for methane-air mixture.

Related formulas

Variables

pThe pre-ignition cylinder pressure (lbs/in2)
p0The cylinder pressure at bottom dead center (usually at 1 atm) (lbs/in2)
CRThe compression ratio (dimensionless)
γThe specific heat ratio (ratio of the heat capacity at constant pressure to heat capacity at constant volume) (dimensionless)