Air Mass Flow Prediction Algorithm

In order to meet the pollutant emissions legislation requirements, spark-ignited engines equipped by a three-way catalyst require a precise control of the Air Fuel Ratio (AFR) fed to the combustion chamber. The AFR control is necessary to assure a stoichiometric mixture for the proper working of the catalyst. In order to guarantee the stoichiometric AFR during transient as well a dedicated Open Loop AFR Control has been implemented. For calculation of the fuel mass to be injected the correct instantaneous air mass flow is necessary. Unfortunately, between the establishment of a certain air mass flow value and the actuation of corresponding injection timing there is an unavoidable delay. In this paper an experimental analysis of this delay on a Fiat Fire 1242 cc 8v is presented. Starting from this analysis the necessity of an algorithm to predict the air mass flow has been discussed. A new air mass flow prediction algorithm has been designed. An implementation of the algorithm on a Normal Production ECU by means of Rapid Control Prototyping tools, has been realized. In this paper the results of the designed algorithm on a Fiat car have been presented.