A method for controlling emissions in the exhaust gas of a diesel engine, the engine having an exhaust gas recirculation (EGR) system. The engine's exhaust aftertreatment system need have only an oxidation catalyst and a particulate filter (with no NOx reduction or adsorption device). In "normal" engine conditions, the engine is operated with a lean air-fuel ratio, with "normal" engine conditions being engine conditions other than transient load increase engine conditions. Also, during normal engine conditions, the EGR system is used to reduce engine-out NOx. During transient load increase engine conditions, the engine is operated stoichiometrically or near stoichiometrically and the use of EGR is interrupted.
Chad P. Koci; Vlad L.C. Ulmet; Stefan Simescu; Magdi K. Khair; Gary D. Neely