What Is Venturi Effect

VENTURI EFFECT

    The engine is in a sense, a vacuum pump. As the pistons move up and down on the intake strokes, a partial vacuum is produced in the cylinder. A partial vacuum is any pressure air, or air-fuel mixture, into the cylinder to fill the vacuum.

    As the air flows toward the engine cylinder, it must first pass through the carburetor. A venturi is located in the air passage through the carburetor. As the air flows through the venturi , a partial vacuum is produced in it, The venturi  restricts the flow air so that the air pressure  in the venturi is reduced. The air particles before the venturi are at atmospheric pressure ( normal air pressure, or particles close together.) But as they move through the venturi, they speed up and spread out ( pressure drops, or a partial vacuum develops).

    The fuel nozzel is located in the venturi. Atmospheric pressure is pushing down on the fuel in the float bowel. Since there is a partial vacuum around the venturi end of the fuel nozzle ( the pressure is lower ), atmospheric pressure pushes  fuel up through the nozzle and into the air flowing  through the venturi. The fuel sprays out, or atmospheric, and quickly turns to vapor.