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To examine the effects of exhaust gas recirculation (EGR) on the exhaust emissions and on the cycle-by-cycle variation of combustion process in a methanol engine, the authors have tried to measure the emissions of total hydrocarbon, carbon monoxides, nitric oxides and formaldehyde and to record the cylinder pressure development histories of 1000 cycles duration. Moreover, the standard deviation of peak pressure Pmax, the heat release rate and the averaged pressure history are analyzed. The results are compared with those of gasoline fueled operation.

Many studies on the Cyclic variation of combustion process are made with a spark ignition engine. However, there are scarcely such studies with a diesel engine. Because, in general, the combustion of diesel engine is believed very stable. However, there exist some combustion variations in a diesel engine. As it is universally known, the combustion in a diesel engineis the series of a pre-mixed and a diffusion combustion, which is completely different from the combustion of a spark ignition engine. Therefore, it is impossible to determine the combustion variation of diesel engine by a direct application of the results of spark ignition engine. In this report, we discuss the several factors which indicate the combustion variation with a pre-chamber type diesel engine. The maximum pressure Pmax, the maximum rate of pressure rise (dP/dθ )max, the combustion pressure at each crank angle, etc. are analyzed from the continuous five handred of combustion pressure histories statistically.