two strokes engine performance

1. Ignition and piston work.
At this point the fuel property will decide the heat release, at which time the fuel will produce work. A well designed fuel is an important factor to race engines. The heat release time from combustion is mainly decided from the fuel properties, air/fuel ratio and cylinder head design. The fuel ratio of H/C (hydrogen/carbon) in the CnHm molecules varies, n and m takes certain values for different fuels. During the combustion, the molecules break down step by step with different heat release at each step. 50% of the available heat is usually released within 5° -10° ATDC (After Top Dead Center).
The picture shows the relationship to crank angle and crank moment. As a schedule example, if fuelblend 1 releases most of the energy in a very short time after TDC with a high pressure peak and blend 2 in a longer period of time with a moderate pressure peak then the moment on the crank will be different over the time for the two cases.
(Pressure in MPa creates an additional piston force)