Heat engines

Carburetor of a heat engine

Carburetor of a heat engine

The carburetor is the device that makes the air-fuel mixture in gasoline engines. In order to make the engine run more economically and obtain the highest power output, it is important that the gasoline is in the best condition. To achieve an optimal air-fuel mixture, the carburetor will use various techniques.

The carburetor basically operates on the same principle as an airbrush. When air is blown across the axis of the spray pipe, the pressure inside this pipe drops. The liquid inside the sprayer is consequently pushed into the pipe and atomized thanks to the friction with the air.

Carburetor Construction and Operation

The carburetor has a division where gasoline and air are mixed, and another where gasoline is stored (float chamber). These parts are divided but connected through the main nozzle.

The air-fuel ratio is decisive in the operation of the engine. The key is that the air must be cold for this performance to be effective.

During the intake cycle of the engine, the piston goes down inside the cylinder and the pressure inside the cylinder decreases, drawing air from the cleaner filter, carburetor and intake manifold, flowing into the cylinder. When this air passes through the narrow portion of the carburetor, it increases the speed (Venturi effect), drawing the gasoline from the main nozzle. This aspirated gasoline is both blown and dispersed by the same air flow and mixed with it. This air-fuel mixture is drawn into the cylinder.

The amount of air entering the carburetor is controlled by the throttle valve, which is connected to the accelerator pedal. This same factor therefore determines the amount of gasoline aspirated.


Carburettor type

Classification of the various types of carburetors

  • Fixed diffuser carburetor. It is a widely used type of carburetor. When the throttle valve opens from the slowed down position, its gauges open progressively.
  • Variable diffuser carburettor. The diffuser section is controlled by a vacuum valve, the function is to increase or decrease the diameter of the diffuser according to the operation of the engine.
  • Double body carburetor. This type of carburetor has a fixed diffuser. It is made up of two bodies or diffusers inside your body. The two throttle valves can be opened simultaneously or one after the other, depending on the type of carburetor.
  • Inverted carburetor. It is a fixed diffuser carburetor in which the air enters from above, vertically.
Publication Date: December 5, 2017
Last Revision: December 5, 2017