Method and apparatus for managing an exhaust gas feedstream for a spark-ignition direct-injection engine

摘要

The disclosure sets forth operating a spark-ignition, direct-fuel injection internal combustion engine equipped with an exhaust aftertreatment system including a lean-NOx reduction catalyst upstream of a second converter element. The engine preferentially operates in one of a homogeneous charge combustion mode and a stratified charge combustion mode based upon temperature of the lean-NOx reduction catalyst. Exhaust gas flow is selectively diverted to the second converter element.