Carburetor – Auxiliary System of Economic Range

carburador - carburetor

This animation sought to be the most realistic to demonstrate the role of the economical track assist system in the carburetor.

The economical range assist system function is to power the engine at the revs of the economical range of fuel consumption, keeping the vehicle at the so-called ‘cruising speed’ with the best ratio distance traveled per liter of fuel, eg km / l.

Animation of carburetor economical range subsystem

With the throttle valve partially opened, the air sucked by the engine accelerates as it passes through the venturi-diffuser or mixing chamber. In the body of the diffuser an intense depression is created – vacuum -, caused by the increase of the velocity of the air in its surfaces – Bernoulli’s Principle and the expansion of the air when surpassing the constriction of the venture. The fuel, which is in the well, is injected to occupy this vacuum because the well’s vent is in a region of higher pressure and the air exerts a force on the surface of the fuel opposite the diffuser.

With the fuel output, and under the effect of increased pressure, the level in the well lowers and uncovers the holes in the mixer tube. The air, which has penetrated through the vent to occupy this space, escapes through the holes and mixes with the fuel, impoverishing the mixture that is injected into the air flow that passes through the carbureted body, in contact with the air the mixture is pulverized and leaves Of the carburetor by vaporizing, under the effect of the temperature in the intake manifold, before proceeding into the inside of each cylinder, by the branches of the intake manifold. The higher the engine speed the more intense this process and a larger mass of air depletes the mixture.


– Changing the color arrow represents the ratio of the air-fuel mixture;
– Cooler colors represent poorer mixtures
– More quantes colors represent richer mixtures
– The size of the arrows represents the volume of air or mixture admitted per unit time (flow rate)

Eduardo Stefanelli

Engenheiro por profissão, professor por vocação