A fully variable hydraulic valve system (FVHVS) for four-cylinder gasoline engines was introduced. In the system

an intake valve was opened by hydraulic oil which was driven by its cam

and seated by the opening of its rotatory control valve

and both its maximum lift and opening duration were governed by the opening timing of its rotatory control valve. All intake valve lifts of the system were measured in a motored valve train test bench. The experimental results show that the maximum valve lift of an intake valve can be continuously varied from 0 to 9.2 mm and the opening duration from 0° to 284° in crank angle. Furthermore

any distortion is not observed in all valve lift curves at the rated engine speed of 5 000 r/min

which means that the FVHVS can meet the demand of high-speed gasoline engines. Moreover

an abnormal opening of intake valve due to mutual interference in a multi-cylinder FVHVS was observed and eliminated by improving the design of rotatory control valves.