Forgasser

A forgasser, or carburetor, is a device in internal combustion engines that blends air and fuel for combustion. It meters the correct amount of fuel and mixes it with air before the mixture enters the engine's intake manifold. The device typically includes a float chamber, needle valve, jets, a throttle plate, and a venturi. Air passes through the carburetor, creating a venturi effect that lowers pressure and draws fuel through jets into the airstream, where it is atomized and carried into the cylinders. The throttle controls airflow, while the fuel metering depends on jet size, needle position, and the choke enriches the mixture for cold starting.

Common designs are updraft, downdraft, and sidedraft carburetors, and configurations range from single-barrel to multi-barrel units. In older cars, the forgasser played a central role in engine performance, starting, and idling. Over time, electronic fuel injection (EFI) provided more precise fuel metering, leading to widespread replacement of carburetors in modern automobiles, though carburetors remain in use on many small engines (lawn mowers, generators, motorcycles) and in some restored or vintage vehicles.

Maintenance issues include varnish buildup from fuel, clogging of jets, and leaks in the float chamber or gaskets. Regular cleaning, correct float height, proper idle and mixture settings, and using appropriate fuels help maintain performance. Environmental and fuel chemistry concerns, such as ethanol content, can affect carburetor performance.