Abstract: An anti-afterburn device for an engine having an air pump, comprising two chambers defined within a housing by a pressure differential piston and a control valve connected to the piston. An intake manifold of the engine is connected to the chambers, at least one of which is connected to the intake manifold through an orifice and an electrically-operated three-way valve so as to operate the control valve through the piston when abrupt pressure change in said manifold is occured or when the three-way valve is energized to communicate the one chamber with a pressure source.

Abstract: An exhaust gas purifying apparatus for an engine, such as a thermal reactor or catalytic converter, is supplied secondary air through a secondary air control valve which is controlled by a combination of a first and a second differential pressure responding device. The first of these devices is responsive to the difference between a constant pressure and varying pressures of the engine manifold and of a secondary air supply means, in order to ensure the suitable secondary air feed, at low, medium and high load on the engine. A connector passage connects a passage of this first device to a pressure chamber of the second device, which actuates the secondary or control valve.