高速公路的发展对客车提出了更高要求。车速的提高对客车的动力性、舒适性、安全性、可靠性和经济性提出了严格的要求。随着国家对环境的重视.要求汽车不但要有良好的性能.而且还要有较低的排放。但国内大客车的动力性能指标与国外相比差距明显,改进其动力系统成为目前的重要问题。 The development of the highway put forward higher requirements for the bus. The increase of speed puts strict demands on the power, comfort, safety, reliability and economy of passenger cars. With the country’s emphasis on the environment, the car requires not only good performance, but also lower emissions. However, the difference between the dynamic performance indexes of domestic buses and those of foreign countries is obvious. Improving the powertrain has become an important issue at present.