Simple adaptive air-fuel ratio control for lean combustion of commercial SI engines

This paper presents the simple adaptive air-fuel ratio control for lean combustion of commercial spark-ignition (SI) engines. In this research, we focus on the strategy for the direct injection fueling control while the spark advance (SA) angle is regulated at maximum brake torque (MBT) by the calibrated look-up table. The experiment conducted on the commercial SI engine show that the proposed adaptive control method has high performance for fueling control on the lean combustion region. Based on this control strategy, we can control the equivalent air-fuel ratio (λ) up to 1.5 without the engine modification. Additionally, the proposed controller shows an effective performance for the disturbance rejection.