Variable valve timing for fuel economy improvement in a small spark-ignition engine

The potential of a simple variable valve timing (VVT) system has been investigated. This system has been designed to update a small displacement engine pursuing the objective of optimizing both engine performance and, particularly, fuel consumption at part load operation. A continuously variable cam phaser (CVCP), able to produce a reverse Miller cycle effect during the intake phase and a significant internal EGR generation at the end of the exhaust stroke, has been introduced. A numerical approach, based on both 1-D and 3-D computational models, has been adopted in order to evaluate the engine performance when load is controlled by the VVT system and to deeply investigate the influence, on in-cylinder phenomena, of the valve timing variation. In this way, the VVT system here analyzed revealed as an effective tool in reducing the pumping losses, hence the specific fuel consumption, at partial load.