The thermodynamic analysis of optimum ignition timing. The effect of cooling loss.

Optimum Ignition Timing is defined as the Minimum Advance for Best Torque (MBT) experimentally. However the relations between the Optimum Ignition Timing and the heat release rate, wall temperature, combustion heat of the mixture, compression ratio, etc. have not been formulated clearly. The problem of this formulation is to integrate the work done on the piston explicitly, because a cylinder volume is not defined as a simple formula of the crank angle. The author presented a simple polynomial of the crank angle for the cylinder volume. Using this polynomial, the author derived the Optimum Ignition Timing formula of the cooled engine as a function of the wall temperature, heat release rate, compression ratio, engine speed, mixture strength, etc.