Abstract
KEYWORDS:
VVA, fuel consumption, multiple cycles, valve deactivation, camless
ABSTRACT
The emission legislation and the customers demands regarding fuel consumption, comfort and performance exerts an increasing pressure upon the process of improving and modernizing the spark-ignition engine. Variable valve actuation (VVA) is used to comply with the conflicting requirements for low emission, good idle quality, high fuel economy and performance. The present paper emphasizes the ways in witch the fuel consumption is influenced according with the VVA systems particularities. Furthermore some operation mode strategies of VVA engines are shown. Those strategies implies the modification of the valve timing and lift, valve and cylinder deactivation, multiple cycle operation, HCCI use according with the regime of the engine. Finally, an example for an evaluation of the fuel economy potential, emission reduction, full load performances, series production feasibility and relative system cost to fuel consumption for developed VVA systems is presented.