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This paper presents an improved exhaust emission simulation model that takes into account fuel transportation behavior in order to obtain more precise air-fuel ratio control, which is needed to meet stringent exhaust emission standards. This simulation model is based on experimental formulas for air and fuel behavior in the intake manifold, especially during transient engine operation. Fuel behavior, including the effect of wall flow on the air-fuel ratio, is obtained analytically. Predictions are then made of the exhaust emissions from a car operated under official driving schedules. The new simulation model is a useful tool in the design and development of fuel supply control systems. An outline of the new model is presented first along with a comparison of the calculated and experimental results. The air-fuel ratio control strategy derived with this model is then described.

The transient performance of an engine generally depends on the volume of wall flow and behavior of fuel in the induction system which is composed of the intake manifold and the intake port. An experimental technique has been developed for estimating these phenomena in a gasoline engine, which employs a meter for measuring the air-fuel mixture ratio. Using this technique we analyzed single point and multipoint injection systems, and determined the differences in the volume of fuel associated with wall flow. The effects of the shape and specifications of fuel supply system components on the volume of wall flow and fuel behavior in these systems were also made estublished.