Review and analysis of variable valve timing strategies—eight ways to approach

Abstract

In internal combustion engines, particularly for spark ignition (SI) engines, valve events and their timings have a major influence on the engine's overall efficiency and its exhaust emissions. Because the conventional SI engine has fixed timing and synchronization between the camshaft and crankshaft, a compromise results between engine efficiency, performance, and its maximum power. By using variable valve timing (VVT) technology it is possible to control the valve lift, phase, and valve timing at any point on the engine map, with the result of enhancing the overall engine performance. To get full benefits from VVT, various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. During the last two decades, remarkable developments have been seen in the field of VVT. This paper reviews the literature in the technology of intake and exhaust philosophies of VVT and their effects on the pressure—volume (PV) cycle of the engine. A single-cylinder engine is simulated by the GT-Power software. The effects of different VVT philosophies from the simulations are analysed and compared to those of the literature reviewed.