Carburetor Carburetor
Actually, the carburetor should be called 'atomizer', as it should mix air with very fine droplets of fuel, meticulously not gas-shaped. Making use of the suction effect of the quickly flowing air, the carburetor should generate for almost all operating conditions a suitable fuel-air mixture. It has been for decades the only mixture formation system for petrol engines. In 1952 the fuel injection was added. Since, however, the introduction of the exhaust gas treatment, the carburetor has out-served. The only exception was the Ecotronic-carburettor.
Really old old-timers featured carburetors with an airflow that went from below upwards (up-draft carburetor), then there was the sidedraught carburetor with horizontally, and the downdraught carburetor (picture) with vertically arranged aerial venturi. The air flows in from above, coming from the air filter, and is substantially accelerated in the narrowing. There, also, ends the duct of the mixing pipe (middle) and the main nozzle (below), which is immerged in fuel. The fuel level in this chamber is held relatively steady by a float control system. A needle valve closes the fuel inflow when the float reaches a certain level.
To the right, left and below the mixing pipe and main nozzle, there are parts of the relatively elaborate idle speed system.