Exhaust-gas regeneration under rich conditions to improve fuel economy

摘要

A method for operating a boosted gasoline engine. The method includes diluting an intake air charge of the engine to a first level of dilution when operating at a stoichiometric air-to-fuel ratio. The method also includes, in response to a condition of excessive exhaust temperature downstream of the engine, diluting the intake air charge of the engine to a second, greater level of dilution while operating at an enriched air-to-fuel ratio.