For simulating an engine cycle, especially of a two cycle diesel engine, it is an important matter how to estimate the gas exchange condition, the unsteady gas flow condition, the matching condition of the engine with its supercharger and some others which affect the scavenging and exhaust processes. In this paper scavenging and exhaust processes including supercharging system are simulated and analyzed under various conditions of the gas exchange, with the authors' new methods characterized by the following items: (1) By using two coefficients as the measures of mixing and heat exchanging between residual combustion gas and fresh air, the gas exchange condition can be simulated and analyzed in any case between complete mixing and complete stratification, so that the computed scavenging efficiency and the computed temperature in cylinder at the beginning of compression agree with the actual ones. (2) The interference effect of pressure in the exhaust pipe of a three cylinder-one charger system, is simulated introducing the coefficient of pressure propagation delay, so that the computed pressure in cylinder at the beginning of compression agrees with the actual one. (3) Partial application of the above-mentioned simulation program to the experimental results of flow measurement gives more reasonable equivalent flow coefficients or turbine efficiency than the ones formerly only assumed or derived from static performance data. By using the results of these simulations and anlyases, can be simultated, pressures, temperatures and flow qualities of gas and air resulting in good agreements with measured values except the case of pressure pulsation. By such simulations under venous conditions the anthers clarified the effects of the followings on the characteristics of the scavenging and exhaust processes: the flow coefficient at the scavenge ports, the gas pressure and temperature in cylinder at the beginning of exhaust. the coefficients of mixture and heat exchange, and the coefficient of pressure propagation delay.