Fuel control system with multiple oxygen sensors

摘要

An exhaust system is provided including two catalysts and three oxygen sensors. The second catalyst is disposed downstream of the first catalyst. The first oxygen sensor is disposed upstream of the first catalyst, the second oxygen sensor is disposed downstream of the first catalyst and upstream of the second catalyst, and the third oxygen sensor is disposed downstream of the second catalyst. A goal voltage corresponding to a desired level of oxygen within the exhaust is provided for the third oxygen sensor based on engine RPM and MAP. The engine controller compares the goal voltage to an actual voltage generated by the third oxygen sensor and an error value is obtained and converted into a goal voltage for the second oxygen sensor. The engine controller compares the goal voltage to an actual voltage generated by the second oxygen sensor and an error value is obtained and converted into a goal voltage for the first oxygen sensor. The engine controller compares the goal voltage to an actual voltage generated by the first oxygen sensor and an error value is obtained and converted into a percent-fuel correction by the engine controller.