Abstract: Mass air flow into an internal combustion engine is measured as a function of throttle opening. The mass air flow rate is expressed as an idle offset constant and the product of gain and effective air intake area which is a function of throttle position. During idle, the idle offset term is updated in response to an exhaust oxygen sensor feedback and during part throttle operation the gain is similarly updated to achieve stoichiometry. For subsonic air flow the mass air flow is further modified as a function of the ratio of manifold pressure to the pressure upstream of the throttle. At the same time the manifold dilution is controlled via an EGR valve to a predetermined schedule.

Abstract: In an internal combustion engine with exhaust means and a carburetor including a fuel bowl, means are provided for delivering fuel to the fuel bowl at a pressure varying in response to the output signal of an air-fuel ratio sensor in the exhaust means to maintain a substantially constant air-fuel ratio to the engine. The fuel supply means may comprise, for example, an electric fuel pump whose input power is varied according to the sensor signal.

Abstract: A combustion engine with a carburetor and exhaust means is provided with an atmospheric air heater such as an exhaust stove. A metering valve supplies a variable mixture of heated air from the exhaust stove and cooler atmospheric air to the carburetor. The changing temperature and hence density of the air supplied to the carburetor produces a changing air-fuel ratio to the engine; and an oxygen sensor in the exhaust system generates a signal indicative of this ratio, which signal is applied through a feedback control system to actuation means for the metering valve to maintain the engine air-fuel ratio at a substantially constant predetermined level.