One of the objectives of this study is to elaborate an engine cycle simulation program in FORTRAN language to analyze the influence of operating parameters on the performance (theeffective power, torque and specific fuel consumption) of a four-stroke gasoline engine (Ford ZSG 416 gasoline engine) for different engine operating parameters. The GT-Powerengine simulation software was used to compare the results obtained with the developed computer program and to improve it. In this program, a single-zone thermodynamicmodel was considered, which describes each phase of the engine cycle. In order to validate the developed program, a comparison of the experimental results with those obtainedusing GT-Power software was carried out. The other objective of this paper is to investigate the influence of a number of significant engine parameters such as compression ratio, cylinder wall temperature, cylinder diameter, stroke-bore ratio and ignition angle on the performance of the chosen engine. Examining the experimental results and those obtained with the developed program, it was observed that the power difference was in the order of ± 3%, the torque difference was ± 6%, while the BSFC difference was about ± 10%. It has been noted that the most significant parameters in improving the performance of the gasoline engine are the compression ratio, the fuel/air ratio, the engine geometry and the ignition begin. The variation of these parameters was not arbitrary, the knock criteria, in other words, the achievement of normal combustion were taken into account.