Valve motion is very important in internal combustion engine because it affects directly and significantly not only on engine efficiency but also on the noise.
In this paper, a four degree of freedom model was set up for an OHV type cam-valve train of diesel engine. The established model was used in computer simulation to enhance valve efficiency by sensitivity analysis. It was found that the valve motion can be improved little by modifying only valve train because the valve motion is almost static. Then it was tried to generate new cam shape, with valve velocity and acceleration constraints, increasing valve motion area. It was found that the valve motion area can be raised by 10.7% without sacrificing valve acceleration and velocity much.
