Closed-loop individual cylinder air-fuel ratio balancing

摘要

The individual cylinder air-to-fuel ratio of an internal combustion engine varies due to the fact that the intake manifold cannot distribute airflow into the individual cylinders evenly. The present invention utilizes the minimum timing for best torque (MBT) ignition timing criterion provided by ionization signals or by in-cylinder pressure signals, along with feedback control, to balance the air-to-fuel ratios of the individual cylinders. The control method of the present invention comprises: calculating a mean MBT timing coefficient 1320, calculating a MBT timing coefficient error 1330, integrating the MBT timing error 1340, calculating a raw fuel trim coefficient 1350, rescaling the raw fuel trim coefficient 1360 and applying saturations (limits) 1370, updating a feedforward look-up table based upon the current engine operating conditions 1370, and calculating a final fuelling coefficient 1380.