Method and system for reducing NOx emissions after a fuel cut off event.

摘要

A method of controlling exhaust emission oxides of nitrogen (NOx) from an internal combustion engine 102 is disclosed which includes the steps of determining when an engine speed is below a first predetermined level and controlling an oxygen displacement valve 130 such that at least a portion of exhaust gas generated by the engine 102 is directed into an intake air flow of the engine 102. The said valve could also be and EGR valve. Preferably the vehicle is a hybrid and the NOx emission control primarily concern is during start up, restarting or stopping of the I.C. engine of the hybrid vehicle.