Parts of a Carburetor

A carburetor system works on three basic principles: metering the correct proportion of fuel and air, atomization of the fuel into a vapor, and the distribution of a uniform mixture of both fuel and air into the engine. When fuel reaches the carburetor, it flows through the fuel supply pipe and into a float bowl. Fuel then flows through the fuel jet into the other side of the carburetor. This side includes an air entry point, also known as the barrel or throat, at which there is an air filter; a Venturi pipe, a tube which varies in width and the throttle valve.

The term "float system" is used to describe a typical carburetor's operation. Fuel flows through the inlet fitting and through a seat, then past the end of the needle and into the float bowl. The needle is important because as the bowl fills up, the float pushes the needle into the needle seat, cutting off the fuel. The fuel stays constant.

The fuel jet is also called the main nozzle. The metering jet, a calibrated opening on the bottom of the float bowl, determines the amount of fuel that will move into the engine. The metering jet opens into a main well which contains air bleeds and baffles that turn the fuel into a vapor as it moves up the main nozzle in a vacuum process, and into the Venturi pipe.

The Venturi pipe is so named because it operates on the Venturi effect. A vacuum is created in the pipe based on how much air is rushing through the carburetor's air entry. The narrow main nozzle moves the fuel into the Venturi pipe by means of low pressure which pulls it out of the nozzle. This spray is then pushed toward the throttle valve.

The throttle valve is placed between the spray and the inlet pipe which leads to the engine. There are two types of throttle valves: the butterfly, which is a circular disc and the cylindrical which is as large as the inlet pipe and rotates. The throttle is controlled by the accelerator, with cables or rods attached to the throttle by a lever. Although the accelerator controls the engine speed, variations made to the throttle valve can be made to enhance a car's performance.

There are several different types, configurations, and manufacturers of carburetors available based on what kind of performance is needed. Different configuration variations include two and four barrel types for more airflow, accelerator pumps, high-flow needles and vacuum secondary diaphragms, just to name a few. Performance carburetor manufacturers include Edelbrock, Holley, AED, Wood and Predator. Small engine carburetor manufacturers include Briggs & Stratton, Bing and Tecumseh, among others. These types include engines for lawnmowers, snow blowers, motorcycle, log splitters and pressure washers.