CATALYST HEATING WITH EXHAUST BACK-PRESSURE

摘要

Embodiments for controlling an exhaust back-pressure valve are provided. In one example, a method for operating an engine comprises closing an exhaust back-pressure valve in response to a component temperature, adjusting intake and/or exhaust valve operation in response to closing the exhaust back-pressure valve to reduce cylinder internal exhaust gas recirculation (EGR), and while the exhaust back-pressure valve is closing, indicating degradation of an exhaust back-pressure system if a designated engine operating parameter remains constant. In this way, degradation of the exhaust back-pressure system may be diagnosed while maintaining combustion stability.

主权项

1. A method for operating an engine, comprising:
closing, via an electronic controller, an exhaust back-pressure valve in response to a component temperature; adjusting, via the electronic controller, an actuator of a variable camshaft timing system to adjust exhaust valve timing in response to closing the exhaust back-pressure valve to reduce cylinder internal exhaust gas recirculation (EGR); while the exhaust back-pressure valve is closing during idle engine speed conditions, indicating degradation of an exhaust back-pressure system if idle engine speed remains constant while intake manifold pressure is maintained at a constant pressure; while the exhaust back-pressure valve is closing during non-idle engine speed conditions, indicating degradation of the exhaust back-pressure system if air-fuel ratio remains constant while intake manifold pressure is maintained at a constant pressure; and responsive to indicating degradation of the exhaust back-pressure system, adjusting, via the electronic controller, an engine operating parameter.