Apparatus and method for controlling the air/fuel ratio of an internal

Abstract

In the subject invention an electronic control unit is used to control the air/fuel ratio in an engine combustion chamber in response to sensed engine parameters. More particularly, a magneto interface produces an ignition signal which is delivered to a spark plug. The spark plug is disposed essentially in the center of a combustion chamber, and it ignites an air/fuel mixture in the chamber in response to the ignition signal. A sensor such as an ion probe, for example, is further disposed in the combustion chamber longitudinally from the spark plug. The sensor produces an ionization signal in response to a flame front propagating past the sensor. A buffer circuit receives the ignition and ionization signals and produces a combustion signal in response to a time difference between the reception of these signals. The electronic control unit receives the combustion signal and calculates a combustion signal air/fuel ratio in response to the combustion signal. Both the combustion signal and the combustion signal air/fuel ratio are responsive to changes in the quality of the fuel in the combustion chamber. Subsequently, the control unit calculates a volumetric air/fuel ratio. The volumetric air/fuel ratio is indicative of the volume of air and fuel in the combustion chamber, and it does not account for fluctuations in fuel quality. Finally, a wastegate is controlled in response to the volumetric and combustion signal air/fuel ratios.