Automatic Control of Cylinder by Cylinder Air-Fuel Mixture Using a Proportional Exhaust Gas Sensor

Cylinder to cylinder air-fuel imbalance in an engine due to geometrical factors and component tolerances may be overcome by a system capable of individually controlling the air-fuel ratio for each cylinder. A stable feedback controller for individual cylinder air-fuel ratio was designed using dynamic models of the gas transport process and the proportional exhaust gas sensor (UEGO). The controller was tested using a proportional exhaust gas sensor located in each bank of a V6 engine. Preliminary test results indicate that automatic balancing of the air-fuel ratio to each cylinder can reduce carbon monoxide emissions compared to a feedback system controlling overall air-fuel ratio.