METHOD (VERSIONS) AND SYSTEM FOR CONTROLLING EXHAUST GAS RECIRCULATION VALVE DURING LEAN OPERATION IN BOOSTED ENGINE SYSTEM

摘要

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