Abstract: An internal combustion engine has an exhaust manifold, an inlet manifold, and a carburetor which has a fuel jet. An oxygen sensor is mounted within the exhaust manifold, and produces an output signal according to the oxygen present within the exhaust gases. A computing means computes a corrective signal according to the oxygen sensor output signal. This corrective signal is fed as an input signal both to a means for supplying secondary air into the exhaust manifold, and also to a means for supplying bleed air to the jet of the carburetor. In a particular embodiment, a secondary air signal cutoff device selectively intercepts supply of the corrective signal to the secondary air supply means, and an air bleed signal cutoff device selectively intercepts the supply of the corrective signal to the air bleed supply means. These cutoff devices may be controlled according to vehicle road speed, engine temperature, engine rotational speed, inlet manifold vacuum, and the temperature of a catalytic converter.

Abstract: Controlled exhaust gas recycling can be accomplished by a pneumatically actuated valve which restricts the flow of exhaust gas from an exhaust manifold of an internal combustion engine to the intake manifold. Exhaust gas may be removed from the manifold and enters a pressure chamber through a reduction means, such as an aperture in a plate. The effective cross-sectional area of hydrodynamic flow of the reduction means is chosen to be greater than the effective cross-sectional area of hydrodynamic flow of the valve. The valve is actuated by a diaphragm control means which is coupled to the intake and exhaust manifold. The diaphragm control means controls the amount of partial pressure applied to the pneumatically actuated valve according to the exhaust pressure from the exhaust manifold.