In the recent years, there has been an increasing interest in the enhancement of the efficiency and functionality of engines, particularly the petrol ones. In this work, the four stroke spark ignition internal combustion engine cycle is simulated based on the first law of thermodynamics. The second law analysis is also been conducted to analyse the effects of the ignition timings and combustion duration as well as the engine speed upon the engine efficiency and performance. The availability (exergy) balance equations of the engine cylinder are considered in details. Moreover, the total availability fractions and process irreversibilities are evaluated. By considering the results obtained for brake and indicated mean effective pressure, it is shown that they behave in an opposite way in terms of increasing the engine speed. After perusing the figures, a conclusion is made, revealing that the exergetic efficiency rises by increasing the engine speed, whereas the opposite is true for the brake thermal efficiency. Furthermore, the optimum point at which the total efficiency (both thermal and exergetic) occurs shows that the highest possible level happens at a speed of 2500 rpm.