Air-fuel ratio control in the multiple cylinder engine

Static performance of the spark ignited internal combustion engine is exmained. To achieve low pollutant levels with good fuel economy there are two engine control strategies. These are, operation at stoichiometric air to fuel ratios with a three-way catalytic converter to reduce or oxidize exhaust pollutants or operation at lean air fuel mixtures. The efficiency of three-way catalysts diminish rapidly as the mixture ratio departs from stoichiometric, while at very lean operation small variations in mixture ratio cause individual cylinders to reach the misfire or lean limit. Either strategy requires accurate control of air/fuel mixture ratio.