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. This feature of the present invention utilizes minimum timing for best torque MBT timing criterion provided by the ionization signals or by the in-cylinder pressure signals to balance the air to fuel ratios of the individual cylinders. The control method of the present invention comprises: calculating a mean timing coefficient, calculating a timing coefficient error, integrating the minimum timing for best torque timing coefficient error, calculating a raw fuel trim coefficient, resealing the raw fuel trim coefficient, updating a feedforward look-up table based upon the current engine operating conditions, and calculating a final fueling command.