Through the tests conducted on a gasoline engine with variable exhaust valve timing, the effects of exhaust valve close timing on the cold-start and its emission performance of gasoline engine are investigated. The test results show that the advance of exhaust valve closing timing, and hence the change of valve timing overlap and the proper increase of in-cylinder residual exhaust gas, can markedly improve the combustion performance of cold-start , shortening start period. Meanwhile the appropriate advance of exhaust valve closing timing is also conducive to the reduction of HC and CO emissions during cold-start.%通过对一台可变排气正时的汽油机进行试验,研究了不同排气门关闭正时对汽油机冷起动及其排放性能的影响.试验结果表明,通过提前排气门关闭时刻,改变气门重叠角,适当增大缸内残余废气量,可以显著改善汽油机冷起动燃烧性能,缩短起动时间.适当提前排气关闭时刻,也有利于降低冷起动过程的HC和CO排放.
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