Effect of Exhaust Runner Length, Valve Timing and Lift on the Performance of a Gasoline Engine

Internal combustion (IC) engine exhaust system can influence the engine’s performance in a significant way. This paper shows that a variable exhaust manifold runner length can improve the engine performance in terms of its output torque by over 10% especially at lower engine speed. Similarly, other exhaust systems such as valve timing and valve lift can improve the performance of the engine in different magnitudes. But when smaller improvements are clubbed together, a significant improvement can be achieved. This paper researches first the exhaust runner length on the engine’s performance. Then, the exhaust valve timing is adjusted to further improve the engine torque produced for the exhaust runner lengths analyzed. Study of a combined effect showed that the runner length requirement shifts slightly as the valve timing is changed. Due to practical limitations foreseen in having longer runner lengths and limitations in the rate of runner length variation, certain areas have to undergo through a region where the torque values are as low as they can be. Though this happens in every single exhaust system out in the market today, valve lift is be used to compensate this loss. In this research the engine torque loss at these points can be regained by 50% by taking the benefit of a variable exhaust valve timing and valve lift system. The combined effect of changing runner length, valve timing and valve lift yields improvements in torques of 2-3% and 7-10% at higher and lower engine speeds, respectively.