A Variable Valve Timing Engine for the Improvement in Engine Performance and Emission Characteristics

A newly designed and developed variable valve lift and timing mechanism is reported in this paper which makes it possible to improve the performance of a single cylinder gasoline engine. This mechanism which was applied to a conventional push-rod, rocker-arm engine, consists of two stages namely phase changer and cam lift duration changer. Consequently valve lift, duration and cam phasing were changed in accordance with engine speed and load. Results of the experiments show that the mechanism functions satisfactory and significant improvements were achieved in power output, fuel consumption, idling quality and exhaust emissions.