Effects of Octane Number on Gasoline Engine Performance

The effects of octane number on engine power output,fuel consumption,exhaust emissions and combustion characteristics were investigated on a gasoline engine complying with China III stage emission standard and a gasoline engine complying with China IV stage emission standard.The test results show that the fuel with excessively high octane number deteriorates the fuel consumption,especially at low or middle loads.The fuel consumption of the engine fuelled with 97# gasoline is up to 6.5 % higher than that of 90# gasoline.When using high octane number gasoline,the engine power of the China IV emission gasoline engine with a knock control system can be improved,and the torque of the engine fuelled with 97# gasoline is up to 4.6 % higher than that of 90# gasoline,but octane number has no significant effect on the power output of the China III emission gasoline engine without knock control system.It is also observed that high octane number fuel increases THC emissions.The results of combustion analysis show that high octane number gasoline suppresses the rate of combustion and increases the combustion duration,resulting in the increase of fuel consumption and THC emissions.