This paper introduces the preliminary simulation of a four stroke spark ignition engine. An arbitrary heat release formula was used to predict the cylinder pressure, which was used to find the indicated work done. The heat transfer from the cylinder. friction and pumping losses also were taken into account to predict the brake mean effective pressure, brake thermal efficiency and brake specific fuel consumption. Most of the parameters that can affect the performance of four stroke spark ignition engines. such its equivalence ratio, spark timing, heat release rate, compression ratio, compression index and expansion index are studied. The use of a real combustion curve has a profound influence on the similarity of the pressure-volume profile to that seen for the real engine. The modeling process is obviously getting closer to reality and is now worth pursuing as a design aid.