Abstract: A system and method for variable exhaust mixing is provided. A variable exhaust mixing device including a butterfly valve is positioned in an exhaust stream and the butterfly valve is opened more to decrease mixing and closed more to increase mixing. The increased mixing provided by the variable exhaust mixing device allows the injection of dosed fuel into the exhaust stream at a lower exhaust flow rate.

Abstract: A method of operating an exhaust valve (28) to heat a diesel oxidation catalyst (23) and to initiate regeneration of a DPF (24) includes the steps of determining whether the DPF is being cleaned, and determining the speed and quantity of fuel injected into the engine. The method also includes determining an engine back-pressure set point based on whether the engine 14 is fueling. If fueling, the set point is based on the quantity of fuel and the engine speed. If not fueling, the set point is based on whether there is an other request for actuation of the exhaust valve (28). An exhaust valve set point is determined based on the engine back pressure set point and a current engine back pressure. The exhaust valve (28) is actuated in response to the exhaust valve set point to obstruct the flow of exhaust gas, where the exhaust gas is heated and initiates regeneration of the DPF (24).