The Influence of Air-Fuel Ratio on Combustion Stability of a Gasoline Engine at Idle 1999-01-1488

A gasoline spark-ignition (SI) engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injection, but the combustion stability at idle is not improved compared to a carburetted engine. The combustion variability in SI engines limits the use of lean mixtures, the amount of recycled exhaust the engine will tolerate, and lower idle speeds because of increased emissions and poor engine stability. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of ignition energy, fuel injection timing, spark timing, and air-fuel ratio on gasoline engine stability at idle.