By the means of the simulation companied by the experiment of GDI engine, the distribution of fuel mixture and soot emission were taken into consideration under different ignition timing. In one injection model, the ignition retard can lessen the soot emission. Two stage spray in cold start, which contributes to catalyst heating operation immediately but triggers a deteriorative performance concerning the soot emission, could be ameliorated by ignition retard. The result shows that the

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... te spray and ignition timing strategy could contribute to the optimization of distribution of air-fuel ratio, streamlining of the circulation variation, the efficient performance, broad confines of extreme circumstance and reduction of the soot emission.