Determination of knock borderline ignition timing in a turbocharged spark ignition engine

The component protection and the thermal efficiency increase are main targets of controlling ignition timing on the knock borderline. The closed-loop knock control is possible with the data analysis، obtained from the knock sensor. However، in this method، the knock prediction and the knock intensity determination are not possible before the knock occurrence. A model to predict the knock and determine its borderline ignition timing، in different engine operating conditions، is presented in this study. These operating conditions، as inputs to the model، were detected using engine sensors'' signals or by simulations in the engine control unit. The effect of the engine speed، the load، the temperature and the intake manifold temperature on the knock occurrence were considered in presented model. The output of the model was knock borderline ignition timing in different combinations of mentioned variables. Experimental results from a modern gasoline turbocharged engine were used to validate the model. Estimated ignition timing from the model was in very good agreement with the experimentally measured knock borderline.