ABSTRACT
From the foregoing chapters, it is known that the main blocks of the gasoline engine are the fuel path and the air path that define the gas mixture entering the cylinder, the combustion block that determines the amount of torque produced by the engine, and the exhaust block with the three-way catalytic (TWC) converter that can remove emissions of hydrocarbon, carbon monoxide, and nitrogen oxide. The catalytic conversion efficiency for pollutant gases significantly depends on the precise value of air-fuel ratio (A/F), since only for a very narrow A/F band around stoichiometry can all three pollutant species (HC, CO, NOx) present in the exhaust gas be almost completely converted to the innocuous components water and carbon dioxide [3, 36, 37]. In addition to the emission concerns, regulating A/F according to the stoichiometric value can also improve the fuel economy and provide efficient torque demands. Therefore, the main goal of A/F control is to maintain the A/F close to the stoichiometric value for efficient combustion, power performance, fuel economy, and optimal after-treatment conditioning, especially during transient operations such as acceleration, deceleration, and load changes.
