System for the detoxication of exhaust gases

In an exhaust gas-detoxicating system for an externally ignited internal combustion engine having at least one air intake suction tube in which a fuel/air mixture is produced by metering into said suction tube fuel from a fuel metering device, and wherein the fuel/air mixture, before its entry into a cylinder of said engine, can be deviated through a heated-up bypass of at least one such suction tube by means of a flap valve being disposed in said suction tube and being controllable in dependence on characteristic engine data,

• the improvement comprising, in combination measuring means for detecting the amount of air flowing through said suction tube and a pneumatic-mechanical converter for controlling said flap valve in dependence on the detected air amount and independently of engine load, wherein said measuring means comprise a Venturi constriction provided in said suction tube, and means for actuating said pneumatic-mechanical converter in dependence on the pressure difference between the air pressure in the narrowest cross-sectional area of said Venturi constriction and the air pressure upstream of said measuring means, and wherein said pneumatic-mechanical converter is connected directly to the flap valve.