In this paper, we report a four-stroke SI single-cylinder laboratory engine with a capacity of 392 cc and a compression ratio of 9:1. For comparison, two methods were used to estimate the mass fraction burned and the resultant heat release intensity. The first method used an experimental model to relate laminar flame speed to temperature, pressure, and air/fuel ratio. This method uses the value of the air/fuel ratio as experimental data. The second method estimated the mass fraction burned and the resultant energy release using the Wiebe function during combustion. The main step in this thermodynamic single-zone modeling is the simultaneous solution of the non-linear first-order differential equations of pressure, temperature, and volume obtained from the ideal gas equation during the cycle. MATLAB solved the nonlinear first-order differential equations; by applying the initial conditions and geometrical specifications of an SI laboratory engine. At the same time, work and cylinder temperature were also determined by applying the first law of thermodynamics and the ideal gas equation and accounting for heat loss. Finally, the results obtained from the flame speed method and Wiebe function were compared with the laboratory results obtained under the same conditions. The studies have shown an acceptable relative agreement.