1.引言预计九十年代中期1.2～2.5L 的轿车汽油机的升功率将达到50kW/L,升扭矩将达到91～97N·m/L。为满足轿车对汽油机的上述动力性能要求,今后这挡汽油机将广泛采用四气门汽油机。现在市场上的第一代四气门汽油机低速区的扭矩特性均不够理想,下一代四气门机应在这方面加以改进。世界范围的排放法规将越来越苛刻,特别是九十 1. INTRODUCTION It is estimated that the ascending power of 1.2 ~ 2.5L sedan gasoline engine will reach 50kW / L and the rising torque will reach 91-97N · m / L in the mid-1990s. To meet the car on the gasoline engine above the dynamic performance requirements, the future this block gasoline engine will be widely used four-valve gasoline engine. Now on the market, the first generation of four-valve gasoline engine speed region torque characteristics are not ideal, the next generation of four-valve aircraft should be improved in this regard. Emissions regulations worldwide will become more demanding, especially 90