Reasons for defects in Simple Carburetor

Simple carburetor is found useful only to a particular load and speed condition. But in actual practice, the engine has to run at different speeds and load conditions.

There are two basic reasons for defects in a simple carburetor.

i) If the carburetor is set or working at high speed and at full throttle condition , it will not work properly at lower speed and part throttle. It is due to insufficient suction created at the venturi for drawing fuel from the main nozzle.

Similarly, if the carburetor is set to work at low speeds and part throttle, it will not work properly at high speed and full throttle.

ii) With the change of pressure heads, coefficients of discharge for air and fuel vary in different quantities. At the certain value of head, the coefficient of discharge for air becomes somewhat constant while in case of fuel it increases gradually. Therefore, at high heads i.e, high engine speeds , the air fuel ratio goes on becoming richer and richer. hence, if the carburetor is set a one particular speed, it will give richer mixture at higher speeds and leaner mixture at lower speeds.

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