The carburettor is an essential component in internal combustion engines that run on gasoline.
Its main function is to mix fuel with air in the right proportions to ensure efficient combustion inside the engine cylinder. Although today electronic injection systems have largely replaced carburettors, these devices played a crucial role in the history of motor racing and mechanical engineering.
History and evolution of the carburetor
The concept of the carburetor dates back to the earliest attempts to develop internal combustion engines in the 19th century. Automotive pioneer Karl Benz designed one of the first carburetors in the 1880s for his three-wheeled automobile. Over time, these devices evolved to improve fuel efficiency and engine performance.
For much of the 20th century, carburetors were the standard fuel delivery system for gasoline engines. However, in the late 20th century, the introduction of more precise and efficient electronic fuel injection made carburetors obsolete in modern cars.
How does an engine carburetor work?
The carburettor is the device responsible for mixing air and fuel in internal combustion engines. Its operation is based on the Venturi principle , which regulates the amount of fuel drawn in according to the amount of air entering the engine.
The process begins with air entering through the filter, which removes impurities. The air then passes through a duct where the Venturi tube is located, a narrowing that causes an increase in the speed of the air flow and a decrease in pressure. This low pressure creates a suction effect that draws fuel from the carburettor tank through a small calibrated hole called a gicleur.
As the fuel is drawn in, it mixes with air and vaporizes, forming a homogeneous mixture. The proportion of this mixture is controlled by several mechanisms, such as the choke, which increases the amount of fuel in the mixture when the engine is cold, and the throttle valve, which regulates the air flow and therefore the engine power.
Once formed, the air-fuel mixture is sent to the intake manifold and distributed to the engine cylinders. There, the spark from the spark plug ignites it, producing the combustion necessary to generate mechanical energy. This process must be precise to ensure efficient engine operation and avoid problems such as excessive fuel consumption or high polluting emissions.
Parts of a carburetor
The carburetor is made up of several parts that work together to properly mix air and fuel. Its main components are:
1. Carburetor body
It is the main structure where the air and fuel ducts are housed, as well as the other internal components.
2. Venturi tube
It is a narrowing of the air duct that generates a pressure drop when the speed of the air flow increases. This effect allows the suction of fuel from the carburetor tank.
3. Gum or chewing gum
It is a calibrated hole through which the fuel passes into the Venturi. Its size determines the amount of fuel that enters the mixture.
4. Float and float chamber
The float controls the fuel level within the float chamber, ensuring that there is a constant supply of fuel to the gicleur.
5. Needle and needle seat
They regulate the fuel flow from the tank to the float chamber, closing the flow when the level is adequate and opening it when more fuel is needed.
6. Throttle butterfly
It is a valve that regulates the amount of air entering the engine, controlling its power and speed.
7. Choke
It is a valve that restricts the entry of air to enrich the mixture when the engine is cold and facilitate starting.
8. Emulsion ducts
They are small channels that help mix the fuel with the air before it enters the intake manifold.
Types of carburetors
Throughout history, several types of carburettors have been developed to optimize engine performance:
- Downdraft carburetor: The most common, where air flows downward through the venturi.
- Horizontal flow carburetor: used on motorcycles and small engines.
- Dual-body carburettor: designed to improve performance in more powerful engines, with two fuel circuits.
- Four-barrel carburettor: used in high-performance vehicles, allowing greater flexibility in the fuel mixture.
Advantages and disadvantages of carburetor
Advantages
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Simple design and easy maintenance.
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It does not require complex electronic components.
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It can be manually adjusted to optimize engine performance.
Disadvantages
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Less fuel efficient compared to electronic injection.
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More sensitive to changes in altitude and temperature.
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Increased emission of polluting gases.
Carburetors today
Despite having been displaced in modern automobiles, carburettors are still used in certain small engines, such as those in motorcycles, lawnmowers and electric generators. In addition, in the field of classic motoring and restoration of antique vehicles, carburettors still have great importance.