valve duration meaning in English

气门开启持续时间

Consequently , to optimize the engine performance in any condition and any circumstances , a need exists for a device that permits variable valve timing , variable lift and variable valve duration during engine operation . so a flexible , hydraulically actuating , electronically controlled variable valve system ( haecvvs ) for model 2135 diesel engine and the experiment bench for its performance have been deve loped
为了能够在任意工况下对发动机的性能进行优化，作者在系统分析了国内外各种可变气门系统的发展状况及特点的基础上，开发了一套中压共轨、液压驱动、电子控制可变气门系统及其性能测试台架，并对电控可变气门系统的性能进行了研究。