Abstract: A method and device for regulating the composition of a fuel air mixture supplied to an internal combustion engine by means of a valve in a secondary air inlet opening into the intake pipe of the internal combustion engine. A detector measures the composition of the exhaust gas and supplies a signal proportional to the oxygen or carbon monoxide content of the gas, this signal is compared with a stabilized voltage, the difference thus obtained is compared with a signal consisting of triangular pulses of a fixed amplitude and the signal thus obtained is used to control the valve after amplification, the duration of the signal defining the time of opening of the valve.

Abstract: A carburettor for an internal combustion engine including a main duct and an auxiliary duct which receive air from a valved inlet, a main valve in each of the ducts for controlling flow through the ducts. Fuel is introduced into the auxiliary duct upstream of the main valve therein but downstream of an auxiliary valve in the auxiliary duct which is used to control the fuel to air ratio of the fuel/air mixture produced by the carburettor. The auxiliary valve is controlled in accordance with engine temperature, pressure drop across air filter, degree of dilution of recycled exhaust gases, degree of combustion of exhaust gases, temperature of air entering the engine, or atmospheric pressure.