A simulation study on the effect of inlet valve opening on performance of high speed engines

Variable camshaft phasing (VCP) system is a potential valvetrain technology for high speed engine applications since it does not increase the effective valve dynamic mass, which is essential to high speed operation. In addition, it is a relatively simple and low cost system. Inlet Valve Opening (IVO) is the start of valve overlap. It has significant effect on engine breathing. As part of a general assessment on the VCP system, such an effect was calculated and analysed using a zero- and one- dimensional based commercial engine simulation package, Lotus Engineering Simulation (LES) and reported in this paper. The simulation was based on a 0.6l, 4-cylinder, 4-stroke, high speed (up to 13500rpm), production spark ignition engine. It was found that IVO can either improve the utilisation of inlet charging effect or reduce backflow during the valve overlap period caused by speed related wave effects from the exhaust manifold.