On-Board Calibration of Spark Timing by Extremum Seeking for Flex-Fuel Engines

An extremum-seeking controller is developed to cope with the calibration complexity for modern internal combustion engines capable of operating with different blends of ethanol and gasoline. The optimization scheme adapts the spark timing such that the fuel efficiency, estimated from in-cylinder pressure data, is maximized on-board a vehicle when driving with small load variations. Experiments, performed in a four-cylinder 2 L engine, demonstrate that the developed controller successfully manages to operate the engine close to the maximum fuel efficiency for different fuel blends, even under mild transient load conditions.