Abstract: In a closed loop air-fuel mixture control system for carburetor-equipped internal combustion engines, an exhaust gas sensor provides a feedback signal to a control unit where the signal is modified to meet the control characteristics of the closed loop. The modified feedback signal is converted into digital pulses whose width varies with the amplitude of the feedback signal. Additional air is supplied to the engine through an air bleed in accordance with the magnitude of the analog feedback signal to provide a coarse control of air-fuel ratio and in response to the digital pulses to provide a fine control of the ratio. The mixture is controlled in a wide range of ratios to eliminate the need for calibration which would be required for fitting the closed loop system to the time-varying characteristics of individual carburetors.

Abstract: An exhaust gas reburning device comprises a first reaction chamber receiving only rich HC and CO containing engine exhaust gases resulting from combustion of a rich air-fuel mixture having an air-fuel ratio lower than a stoichiometric air-fuel ratio to cause effective oxidation of rich HC and CO in the engine exhaust gases and a second reaction chamber separated from the first reaction chamber and receiving the resultant engine exhaust gases from the first reaction chamber and poor HC and CO containing engine exhaust gases resulting from combustion of a lean air-fuel mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio to effect sufficient oxidation of lean HC and CO in the engine exhaust gases of the lean air-fuel mixture and the remaining HC and CO in the resultant engine exhaust gases from the first reaction chamber by heat of the resultant exhaust gases and oxygen in the lean HC and CO engine exhaust gases.