EXHAUST GAS AFTER-TREATMENT SYSTEM

摘要

An exhaust gas after-treatment system (l0) for a gasoline engine (12) has a three-way catalyst (14) close-coupled to the gasoline engine, a particulate matter control device (18) positioned downstream of the three-way catalyst, a NOx control system (16) positioned downstream of the particulate matter control device. According to one method of operation, the gasoline engine is operated in a stoichiometric condition upon start-up of the engine, the exhaust gas flow generated by the engine is conducted through the exhaust system, and then the gasoline engine (12) is operated in a lean-burn condition after the NOx control system (16) attains a minimum operating temperature.