A case study of cyclic balancing control for SI engines

Cyclic variability is an important index for SI engine in steady operation mode. In this paper, a cylinder pressure related index is proposed for cyclic variability indirectly. Firstly, under the steady mode with all fuel injections fixed to their nominal value for each cylinder, an ARMA model to describe the dynamics from ignition time to 4 cycle moving average of the pressure related index is validated by experiments and the model-based Minimum Variance Control(MVC) is executed. Furthermore, this model is transferred into the other operation mode where fuel injection adjusts with individual F/G balancing to eliminate inlet fluctuation effect brought from cylinder imbalance and improve fuel efficiency. In F/G balance control, an estimation model for F/G of each cylinder from A/F sensor placed in the exhausted manifold is executed. Finally, the validation of the indirect cyclic variability control under F/G balancing is tested by experiments.