Variable Valve Train systems as contribution to overcome the NO_x/CO₂ Trade-Off in meeting future emissions legislation - a comparative approach for Diesel PC and CV applications

Abstract

Schaeffler offers electromechanical, discretely switchable valve lift systems for passenger car applications, e.g. the eRocker system and is inventing a commercial vehicle application solution: the Schaeffler electromechanical switchable rocker arm system. This modular valve train system can be integrated easily in existing engine setups regardless of the camshaft position and number. Both systems support exhaust aftertreatment heat-up and efficient exhaust gas thermal management at extended low load operation. To meet future emission legislations, Schaeffler and IAV investigated various thermodynamic strategies via simulation and experiments on a passenger car, and simulations on a heavy duty diesel engine. Innovative valve lift strategies like early intake valve closure in combination with secondary exhaust valve opening are compared to existing conventional strategies like intake air throttling and combustion late phasing. The results for both passenger car and heavy duty diesel engines show significant potential to increase the exhaust temperature with optimized fuel consumption. This publication summarizes and compares the contribution of innovative valve lift strategies for efficient exhaust gas thermal management for passenger car and commercial vehicle applications.