Development of an electrical control VVT system for high speed SI engines

A newly developed electrical control variable valve timing (VVT) system is presented which is applied by changing the intake valve closing timing based on the variable working position extender. It has some advantages such as its simple structure, little modification for the engine, easy installation and low cost etc. The test results show that the engine performance is modified distinctly, such as the torque at low speed, the output power at high speed, the fuel economy and the emission in some conditions. This VVT system is suitable for use in the high-speed automotive engines with double overhead cam (DOHC)