An Electro-Hydraulic “Lost Motion” VVA System for a 3.0 Liter Diesel Engine

Abstract

IVECO Motorenforschung AG launched in the early 1990's a program to study the potential of a variable valve actuation (VVA) system for diesel engines. The simulation results and measurements with special cam profiles encouraged IVECO to analyze an engine with a VVA system. A hydraulic system was identified as being the best solution to implement the selected valve timing strategies and Jacobs Vehicle Systems was selected as partner to jointly develop the VVA system. This paper presents the design considerations and performance results for the application of an electro-hydraulic lost motion Variable Valve Actuation System (VVA) on a 3.0 liter four-cylinder 16 valve DOHC Dl Diesel Engine equipped with a common rail fuel injection system. The VVA system is applied such that both intake and both exhaust valves are actuated in tandem. It will be shown that the VVA system allows adequate flexibility in valve actuation to optimize cylinder charging and low-end torque with simultaneous improvements in fuel consumption and drivability. One of the most interesting aspects of such a VVA system applied on a Dl Diesel Engine is the potential to provide extremely fast and accurate control of the internal EGR rate. This is possible by actuating the intake or exhaust valves of each cylinder at specific instances during the exhaust or intake strokes. Improving engine start-ability and warm-up by varying compression ratio and cylinder deactivation will be also discussed. Additional benefits include the control of exhaust gas temperature for improved catalyst efficiency / DPF (Diesel Particulate Filter) regeneration and the possibility to integrate a reliable engine brake system in a relatively simple and cost-effective way.