US Patent 8635852 Exhaust treatment system for internal combustion engine

Methods and systems are provided for operating an engine including an exhaust treatment system coupled to an engine exhaust, the exhaust treatment system further coupled to an engine intake via an exhaust gas recirculation (EGR) system. One example method comprises, operating in a first mode including routing exhaust gas through the exhaust treatment system to an exhaust tailpipe; operating in a second mode including routing exhaust gas through the exhaust treatment system to an engine intake via the EGR system, and operating in a third mode including routing exhaust gas to an engine intake through the EGR system while bypassing the exhaust treatment system.