A method and system for controlling an EGR valve during lean operation in a turbocharged engine system

摘要

Methods and systems for reducing EGR estimation errors during lean engine operation conditions are provided. During lean engine operation, the EGR is disabled if an estimated exhaust air-fuel ratio becomes leaner than a lean threshold. The lean threshold is set based on an upper limit of the EGR errors that may be tolerated by the engine at a given engine speed and load.