The VTEC engine, developed by Honda, is a valve control system that can simultaneously control valve opening and closing time and lift. Compared with the ordinary engine, VTEC engine is different in the number of CAM and rocker arm and control method, it has two different groups of low speed and high speed valve drive CAM, and can be adjusted by the electronic control system for automatic conversion. Through the VTEC system device, the engine can automatically change the opening time and lifting degree of the valve according to the driving condition, that is, change the intake and exhaust volume, so as to achieve the purpose of increasing power, reducing fuel consumption and reducing pollution.