A method and system for controlling recirculated exhaust gas composition and quantity provided to an internal combustion engine, which has one or more separately controllable combustion cylinders, a main exhaust line and an exhaust gas recirculation (EGR) loop. A first exhaust valve is connected to the main exhaust line, and a second exhaust valve is connected to the EGR loop. The operation of the exhaust valves is controlled such that exhaust does not flow through both exhaust valves at the same time. Control of the exhaust valves is coordinated with the main fueling event used to control the exhaust composition exiting each valve for every cylinder on every cycle. During each engine cycle, a post-combustion fuel injection event is also used to add fuel to the exhaust in-cylinder, which flows only through the second (EGR) exhaust valve.
Terrence F. Alger II; Jess W. Gingrich