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 too[ in reducing the pumping losses, hence the specific fuel consumption, at partial load. (c) 2008 Elsevier Ltd. All rights reserved.