This paper deals with the development and evaluation of a mathematical model for a 4-stroke, single-cylinder, spark ignition engine. This paper has two parts. The first part describes the development of the mathematical model and the computer program. The assumptions that were made in the model are also described. The instruments that were developed for the evaluation of the model are included in the second part, which also contains the evaluation of the results obtained from the model. The simulation results are found to agree well with the experimental data.