The application of a microprocessor to engine cylinder disablement

The power output of a spark ignition, internal combustion engine is normally controlled by the use of a throttle on the air intake system. As a result, the part-load efficiency of the engine suffers when compared with the compression ignition engine. A microprocessor development system was adapted for use with the electronic fuel injection of a 6 cylinder, spark ignition engine in order to selectively· disable any number of individual cylinders by interrupting the fuel flow from the injectors of those cylinders. The system allows any number and combination of cylinders to be. disabled cyclically, with the view of keeping all cylinders hot and minimising engine vibration. The theory of cylinder disablement, and work published in this field are discussed in this Thesis. Also included are the results of engine testing carried out to determine the economy gains possible with cylinder deactivation, and to investigate the behaviour of a cylinder under disablement, and subsequent reactivation by control of its injector. The relationship between cylinder deactivation sequence and engine vibration, and means of minimising the amplitude of that vibration were also investigated, and the results obtained discussed, together with the results of limited emission and fuel consumption testing of a vehicle fitted with cylinder disablement. The main conclusions reached at the end of this research were: (i) The use of a microprocessor system, in conjunction with electronic fuel injection to disable cylinders by control of their injectors is an effective way of implementing cylinder disablement. ( i i) Fuel economy gains achieved· varied from over 50% at idle to 25 - 45% at light load, steady state conditions, with actual vehicle tests returning almost 40% fuel.economy over the European 04 Test driving cycle, accompanied by moderate increases in exhaust pollutants. (iii) Engine vibration, resulting from the imbalance of the non-firing cylinders can be reduced to acceptable levels by arranging the disabled cylinders according to their firing order and engine speed, as shown in this Thesis. Finally, the possibilities of expanding the microprocessor · development system used for this research, to incorporate the additional disablement control features, are discussed and recommendations made, based on the results of the research.