What is a Carburetor?

N. Madison
N. Madison

A carburetor, called a carb for short, is a device used in an internal combustion engine, such as the type found in an automobile. Invented by Karl Benz in the 1800s and patented in 1886, a carburetor’s job is to mix air and fuel. Up until the mid-to-late 1980s, these devices were the primary fuel-delivery method for engines. After that time, fuel injection took over as the most used method for fuel delivery, as it is considered more efficient and better in terms of emissions. In fact, the mid-to-late 1990s saw an end to the carburetor’s use in new cars.

Carburetors are still common in motorcycles.
Carburetors are still common in motorcycles.

Though carburetors have lost their places in most cars, they are still used in motorcycles. However, this may come to an end as many newer models also go over to fuel injection. As for now, carburetors continue to have a place in small engines, and they can be found in some specialized vehicles. For example, carburetors are still used in vehicles built for stock-car racing. Carburetors are also found in small-equipment engines, such as those found in lawnmowers.

Fuel injection systems supply fuel directly to the cylinders of a vehicle's engine.
Fuel injection systems supply fuel directly to the cylinders of a vehicle's engine.

All carburetors follow a basic type of construction. Basically, a carburetor consists of a tube with an adjustable plate across it. This plate is called the throttle plate and controls the amount of airflow. A narrowing in the tube is called the venturi, which creates the carburetor's vacuum. Within the vacuum is a jet, which is a hole that allows the vacuum to pull in the fuel.

To understand how a carburetor works, you have to look at Bernoulli's principle. This principle explains that the speed of air affects its pressure. When it moves faster, its pressure is lowered. Some people think the throttle pedal or accelerator controls the flow of fuel when a carburetor is used. Instead, the accelerator starts certain carburetor actions, leading to the measuring of air as it is drawn into the engine.

The speed of the airflow, as regulated by the carburetor, influences the pressure and regulates the amount of fuel that is supplied to the engine's air stream. The job of the carburetor is not at all trivial. If the device fails to get the mix just right, the engine will not run properly. When too little fuel is blended with the air, the engine runs lean, fails to run at all, or suffers damage. When too much fuel is allowed in, the engine floods, wastes fuel, emits too much smoke, or gets bogged down and stalls.

N. Madison
N. Madison

Nicole’s thirst for knowledge inspired her to become a wiseGEEK writer, and she focuses primarily on topics such as homeschooling, parenting, health, science, and business. When not writing or spending time with her four children, Nicole enjoys reading, camping, and going to the beach.

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Discussion Comments


@bivie - When you decide to turn that old truck into a new one, you won't have to worry too much about that. The fuel injection systems on new vehicles don't have that same problem. That's because when you go to a higher altitude into the thinner air, your vehicle's injection system will compensate for it -- for the most part.

The injector is designed to detect that situation with the thinner air, so you will be all right except for when you are at slower speeds. It won't spit and sputter, but it might not have quite as much giddy-up. It's nothing radical, and you may or may not notice it.


Well, that explains a few things. I recently took a trip up into the mountains and my old truck started acting up. I figured it was a fine time for my truck to act up while I was so far away from home. It acted up on the whole trip until I got about half the way home. I decided it must have been some dirt or something caught in the fuel line.

Obviously, I don't know much about cars. But I do now; well, at least a little more. It occurred to me while reading this that the air is thinner up in the mountains, and I realize my truck wasn't getting enough air into the "carb," as you called it (I might as well learn the lingo too). I won't have to get a carburetor rebuild, but I will have to figure out how to adjust it next time I go camping. Thanks for the heads up.

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