Influence of direct injected timing on the performance in a spark ignited dual-injection gasoline engine for an automotive under various injection modes

Influence of direct injected timing (DIT) on the performance in a spark ignited port- and direct-injected (PI and DI) gasoline engine was studied experimentally. The results show that the best BMEP (brake mean effective pressure) and BTE (brake thermal efficiency) can be obtained at DIT = 280 degrees CA bTDC. At a constant DIT, the BMEP and BTE of DI50 (50 % PI and 50 % DI of gasoline) injection mode (IM) are higher than those of DI100 (0 % PI and 100 % DI of gasoline) IM. The highest cylinder pressure, highest heat release rate and highest cylinder temperature can also achieve the maximum at DIT = 280 degrees CA bTDC and various IMs, and their crank angle (CA) positions are closer to TDC (top dead center). The PI + DI IM is more propitious to ameliorate the combustibility of engine and carry out more stable combustion than DI IM. The DIT and IM have a significant influence on CO and NOX emissions. The DIT has a little influence and IM has an crucial influence on HC emission. The soot emission increases slightly with delayed DIT at DIT>80 degrees CA bTDC, and then increases rapidly with further delayed DIT at DIT<80 degrees CA bTDC.