A quasi-dimensional spark-ignition (SI) engine cycle model has been developed. In this model, combustion is modeled as a turbulent flame propagation process. During the combustion, it is assumed that the cylinder charge consists of unburned and burned gas zones. A computer code was developed for the mathematical cycle model presented. By using this code for any engine running at specified conditions, parameters that characterize the combustion, cycle, and engine performance can be computed practically. The above-mentioned parameters for several engines with different geometries and running at different operating conditions are determined theoretically, and these predicted values are compared to experimental data given in the literature. Good agreement between predicted and experimental results is obtained. Comparisons of predicted and measured results show that the presented model is reliable for analyzing SI engine cycles.