Method and system for pre-ignition control

摘要

Methods and systems are provided for addressing pre-ignition occurring while operating with blow-though air delivery. A variable cam timing device used to provide positive intake to exhaust valve overlap is adjusted in response to an indication of pre-ignition to transiently reduce valve overlap. Pre-ignition mitigating load limiting and enrichment applied during a blow-through mode is adjusted differently from those applied when blow-through air is not being delivered.

主权项

1. A method for a boosted engine, comprising:
while operating in a blow-through mode, reducing positive valve overlap of an intake and exhaust valve by adjusting a valve actuator in response to an indication of preignition, including a pre-ignition count increasing, and adjusting ignition timing responsive to knock, pre-ignition indicated in response to knock sensor output before a cylinder spark event, knock indicated in response to knock sensor output after the cylinder spark event.