Cylinder Individually Gas Exchange Controlling: A Method for Improved Efficiency of Turbocharged SI Engines

Combustion concepts for future SI engines try to meet CO₂-emission legislation all over the world. One approach is to minimize the gas exchange losses using a fully variable valvetrain on the engine’s intake side, or the reduction of the throttled part load operation either by downsizing concepts in connection with turbochargers or by deactivation of cylinders. An interesting strategy is the utilization of proven CVVL-components to find effective controlling methods for the combustion process of turbocharged direct injection SI engines. The new approach of using a fully variable valvetrain on the exhaust side improves the controlling of both residual gases and combustion processes. A camless valvetrain provides the opportunity to control air mass flow and combustion process for every single cylinder of a multi-cylinder engine to achieve best performance in fuel efficiency at part load operation combined with enhanced transient response of turbocharged engines. The latter is particularly important for operation with cylinder deactivation where an improvement by different operation of individual cylinders is possible compared to the complete deactivation of the cylinders. The West Saxon University developed a fully variable electric-hydraulic valvetrain for a four-cylinder turbocharged engine. The valvetrain is able to control every cylinder individually. In order to find the best control strategy numerical studies on the potential of cylinder-individual control were conducted with respect to engine part load and transient operation. The basic model was evaluated by means of a fired engine on a test bench. This paper presents results from numerical simulations regarding gas exchange losses and fuel efficiency of a multi-cylinder engine whose cylinders are each fully variable on the intake and exhaust side. The simulations show the potential of the new way of air mass control, thus research can progress toward testing on a running engine.