The tuning of a small four-stroke spark ignition engine for flexible valve timings through numerical approach

Variable valve timing has been implemented by various manufacturers to improve internal combustion engine performance while operating at wide speed and load ranges. A novel flexible valve timing system for a small four-stroke engine is currently under development by Automotive Engineering Research Group (AERG) in Universiti Malaysia Pahang (UMP). In this paper, a compherenhensive intake and exhaust tuning for th flexible variable valve timing is presented. A numerical assessment has been conducted to the engine in a one dimensional engine simulation using validated simulation model. There are eight valve timing configurations investigated for the tuning for three speed regions. The simulation shows a positive and significant impact to the engine performance in three approaches; namely late intake valve closing, early intake valve closing and late exhaust valve closing. These approaches sufficiently covered the whole range of engine speeds.