A study of cooling system of a spark ignition engine to improve thermal efficiency

To improve thermal efficiency of gasoline engines, the effect of coolant system on fuel consumption rate is studied in this report. The authors tried to control the flow of cooling water to find an optimized flow system to improve thermal efficiency, especially for the cold start condition. Experiments were carried out using a four-cylinder SI engine. Three test conditions of i) normal cold start, ii) cold start without operating the water pump and iii) cold start but with heated engine oil were measured. Temperatures of cooling water at some positions were measured during the warming-up time. Secondly, the effect of cooling water temperature on thermal efficiency at a steady state condition was examined. As a result, a higher temperature causes an improvement of thermal efficiency due to a reduction in mechanical friction.