为了减少或避免发动机废气污染,人们首先在发动机外围想办法,如催化器、废气回收、电喷等等。目前研究方向转向了发动机内部,如进气调节、燃气混合、点火强度等等。最后一些公司又在进排气控制系统上下功夫。如保时捷公司在其911型轿车上采用双行程进气门,宝马公司研究机电一体化 In order to reduce or avoid engine exhaust pollution, people first think of ways around the engine, such as catalytic converters, exhaust gas recovery, EFI and so on. The current research direction turned to the internal engine, such as intake adjustment, gas mixing, ignition intensity and so on. Finally, some companies work hard on the intake and exhaust control system. Such as Porsche in its 911 sedan with dual-stroke intake valve, BMW’s research Mechatronics