In view of the different characteristics of closed valve injection(CVI) and open valve injection(OVI)

the effect of OVI on the performance of a port fuel injection(PFI) gasoline engine was studied by bench test and numerical simulation. Results show that at 20% of the throttle valve opening degree

the earlier injection timing can make engine output power increased by 0.2 kW and the HC emission decreased by 30×10-6 compared with the later injection timing However

when the throttle valve opening degree is up to 100%

the injection timing on engine power and emission is negligible due to the influence of intake airflow and cylinder temperature. In addition

at 20% of the throttle valve opening degree

the proportion of non volatilized fuel is about 50% of the total fuel injection quantity while at full throttle

the non volatilized fuel accounts for only 15% of the total fuel injection quantity. It can be seen that no completely volatilized fuel is main reason for the decline in OVI engine performance. Therefore

improving fuel volatility is the main way to improve the performance of OVI engine.