An exhaust gas recirculation (EGR) system for an internal combustion engine having dedicated EGR and operating at a net stoichiometric air-fuel ratio. In such engines, one or more cylinders is operable as a dedicated EGR cylinder, such that all of the exhaust produced by the dedicated EGR cylinder(s) may be directed back to the intake manifold. Because the engine's exhaust is net stoichiometric, its exhaust aftertreatment system has a three-way catalyst. An EGR loop is configured to recirculate EGR from the dedicated EGR cylinder(s) to the engine's intake manifold. A diversion line, modulated with a valve, connects the EGR loop to the exhaust aftertreatment system, thereby allowing adjustment of the relative amounts of EGR to be recirculated and to be provided to the exhaust system.
Cary A. Henry; Terrence F. Alger; Jess W. Gingrich