Intake Manifold Modeling for the Fuel Metering Control of Spark Ignited Engines

Abstract

In order to minimize emissions the Air-Fuel Ratio (AFR) of a spark-ignited internal combustion engine needs to be maintained at stoichiometric. Whenever the air and fuel enter the engine’s cylinder the AFR cannot be changed; therefore the problem of AFR control is a problem of intake manifold control. Although the problem of AFR control (and hence of intake manifold modelling) appears to be solved for a fully warmed-up engine the problem of AFR control during the warm-up period remains. This paper addresses this problem by using a novel AFR control strategy, which can be based on a given intake manifold model, to test the AFR control of a partially warmed-up engine. The results of engine tests demonstrate that during the warm-up period tight AFR control is not possible using any of the intake manifold models developed for a fully warmed-up engine. This can only be the result of unmodeled dynamics in the intake manifold and it is therefore concluded that further work in the area of manifold modelling is required. Possible areas of model improvement are indicated.