Method and system for improved dilution purging

摘要

Methods and systems are provided for expediting EGR purging in a hybrid vehicle during transient operations, such as tip-out to lower load conditions. In response to decreasing engine torque demand, engine fueling is disabled and a motor is used to spin the engine unfueled until a desired LP-EGR rate is achieved. Alternatively, engine operation is maintained with EGR disabled until the desired LP-EGR rate is achieved, and the excess engine torque generated is stored in a system battery.

主权项

1. A method for a hybrid vehicle, comprising:
in response to decreasing engine torque demand while operating an engine with EGR,
disabling EGR; and until EGR in an engine intake is less than a threshold,
operating the engine, fueled, with EGR disabled and propelling the vehicle with engine output torque higher than demanded torque for vehicle propulsion; andcharging a system battery.