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Delco Rochester Basic Carburetion

Basic Principles of Carburetion

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    A carburetor is a metering device which mixes fuel with air in the correct proportions and delivers them to the engine cylinders as a combustible mixture.

    The automobile engine's source of fuel for power is gasoline. In liquid form, however, the gasoline is of little use; its energy can be released by combustion, only when combined properly with the correct amount of air and delivered to the cylinder of the engine as a combustible mixture.

mixture flow regulation which gives the driver control of the engine speed.

    Regardless of engine r.p.m. or load the engine encounters the carburetor must automatically perform its three basic functions.

    The automotive carburetor is a very intricate device; however, when studied one phase at a time, the functions of the carburetor are easily understood.

    As mentioned above, the three main functions of the carburetor are to meter, atomize and distribute the fuel.


    The purpose of a carburetor on a gasoline engine is to meter, atomize, and distribute the fuel throughout the air flowing into the engine. All of these functions are designed into the carburetor and are carried out by the carburetor automatically over a wide range of engine operating conditions, such as varying engine speeds, load, and operating temperature.

    The carburetor also regulates the amount of air/fuel mixture which flows to the engine. It is this

Metering (Fig. 2)

    Good combustion demands a correct mixture ratio between fuel and air, commonly called the air/fuel ratio. Too much fuel results in a "rich" mixture, while too little fuel results in a "lean" mixture. To release all possible energy by combustion, the right amount of fuel must be mixed with a given amount of air. The metering job of the carburetor is to furnish the proper air/fuel ratio for all conditions, so that the engine operation will neither be too lean for power requirements or too rich for economy.

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