Abstract
The performance of an engine whose basic design parameters are known can be predicted with the assistance of simulation programs into the less time, cost and near value of actual. However, inadequate areas of the current model can guide future research because the effects of design variables on engine performance can be determined before. In this study, thermodynamic cycle and performance analyses were simulated for various engine speeds (1800, 2400 ve 3600 1/min) and various excess air coefficients (EAC) (0.95-1.05) to crank shaft angle (CA) with 1 degree increment at full load and 8:1 constant compression ratio (CR) of a SI engine with four stroke, single cylinder and natural aspirated. Brake mean effective pressure, power, thermal efficiency, specific fuel consumption (sfc), etc engine performance parameters were calculated; the values of peak cylinder pressures and temperatures and positions of them were determined by the present program. Variations of these parameters with crank angle, engine speed and excess air coefficient were presented graphically. The calculated results show good agreement with literature. Simulation program is usable to set for varies load, compression ratios, and engine sizes.