Turbocharged i.c. engine with variable-geometry turbine (VGT) and exhaust gas recirculation (EGR)

摘要

A method and system for controlling an engine 10, eg a direct-injection lean-burn engine, having an EGR system 12 and a turbocharger 14 with a turbine inlet flow control device having at least two discrete positions is disclosed. The turbocharger may be a VGT turbocharger with movable vanes or with fixed vanes and movable shutters or flapper valves. The method includes producing a control signal having two discrete levels, one of which is selected to provide a proper flow of air through the turbocharger 14 to an intake 26 of the engine and modulating the signal between the two levels to provide, over time, a proper pressure at an input of the exhaust gas recirculation system 12 to enable a proper flow of exhaust gases from an exhaust 28 of the engine 10 through the exhaust gas recirculation system 12 back to the intake 26 of the engine 10. The system is less expensive and more robust than one with a continuously adjustable VGT device.