Effects of Valve Overlap, Lift, and Duration on Spark Ignition Engine Performance

This study aims to investigate the effects of valve motion characteristics on the performance of spark-ignition engines. The impact of valve timing, valve lift, and valve duration on the full-load performance characteristics of the engine was analyzed through modeling. For this purpose, the WAVE simulation program, one of the one-dimensional gas dynamics simulation tools, was used. The Taguchi experimental design method was applied for the simulation design of the variables. An analysis of variance (ANOVA) was conducted to examine the relationship between engine performance and valve motion characteristics. A total of 125 simulations were conducted, with 25 solutions for each engine speed. Brake torque, brake thermal efficiency, and volumetric efficiency were chosen as engine performance parameters. Based on the ANOVA, the optimal valve motion characteristics that maximize these three engine performance parameters simultaneously were determined. The results showed that valve overlap and intake valve duration were the most influential parameters affecting engine performance. Moreover, compared to the reference engine's original configuration, increasing valve overlap and reducing intake valve duration improved engine performance. A comparison was made between the optimized values and the original values of the reference engine. While the original configuration of the reference engine performed better at high engine speeds, a significant improvement in engine performance was observed at low and medium engine speeds. Specifically, for low and medium speeds, improvements of 8.1% in brake power and brake torque, 1.5% in brake thermal efficiency, and 6.8% in volumetric efficiency were observed.