Analysis of ignition at different fuel injection timings in gasoline direct injection engine

The fuel injection technology largely determines the fuel-air mixture quality and emissions formation during engine combustion. With gasoline direct injection technology, spark-ignition engines have shown enhanced power output and fuel economy. However, the influence of fuel injection parameters needs to be understood properly so that it can be optimized for improved performance. Further, the ignition timing should be tuned depending on the fuel-air mixture formed via different fuel injection timings. This study evaluated the effect of ignition timing for three different fuel injection timings, corresponding to early, mid and late intake stroke. The analysis was done by examining the combustion, performance, and regulated emissions characteristics. The test conditions were operated at fixed engine speed of 1500 rpm and torque of 20 Nm with a stoichiometric mixture. The results showed that late fuel injection resulted in early pressure rise while mid-intake injection retarded the combustion. However, the early injection led to faster combustion with the highest combustion efficiency. The brake thermal efficiency of the engine was higher for early injection and increased with ignition advance. Carbon mono-oxide and hydrocarbon emissions were lowest for early injection; however, it resulted in increased NOx emissions.