What is a carburetor and how it works – scheme and device
Some motorists may think that the information about what a carburetor is not particularly important, since injectors are actively used today instead of these devices. But it is the carburetor engines are still used on many cars, so we decided to help their owners understand the principle of operation of the carburetor and its device.
The history of the carburetor began back in 1876, when Italian Luigi de Cristoforis invented this device. A few years later, Carl Benz began working on his own version of the carburetor during the creation of the first car with an internal combustion engine. We suggest studying our article on how a car engine works. In the late 1920s, the float-type carburetor appeared, which was later used as the basis for the release of more modern modifications. Considering etymology, the term “carburetor” came from the French word “carbure,” which can be translated as “carbide.” Since the word “carburer” is used to refer to a compound with coal, in chemistry it is used to refer to increasing the carbon content of a liquid and mixing it with volatile hydrocarbons. The latter compound is a component of crude oil, from which diesel and gasoline are made. It’s time to talk about why the carburetor was a very important component of most 20th century engines. In the 1980s, there were a lot of changes in the world. In particular, instead of the carburetor, whose device was considered obsolete, car companies began to make extensive use of fuel injection technology. Although carburetor engines are still used in cars created for racing competitions like NASCAR, it is almost unreal to meet them in modern models.
How the carburetor works
As you know, the operation of modern internal combustion engines consists of four cycles, which is why these engines are called four-stroke engines. Almost all motorists understand what cycles we are talking about: intake, compression, stroke, exhaust. Let’s take a closer look at the principle of the car carburetor itself. In simple words, in order to burn gasoline, the carburetor must mix the required amount of it with the appropriate amount of air. If the resulting mixture contains too much fuel, it will cause the cylinders to fill up and produce a huge amount of exhaust. Having too little fuel in the mixture is also not conducive to proper engine operation. The design of the carburetor includes a throttle plate. This is an adjustable plate that controls the amount of air flowing through the carburetor. The constriction is called a diffuser, which is used to create a vacuum. It has a small hole in it, which is called a nozzle. Through it takes fuel from the fuel line connected to the gas tank. When the gas pedal is pressed, a valve is opened that limits the amount of air that enters the carburetor. If the pedal is depressed as much as possible, the valve will open fully, resulting in a large amount of air flowing through the carburetor. The engine will eventually get a fairly rich mixture, which will result in an increase in horsepower. When the engine is idling, the valve is closed, but even in this case, the jammer provides a small amount of fuel bypassing the throttle, which ensures the stable functioning of the power unit. Owners of VAZ “classics”, as well as other cars produced several decades ago, are well aware of what a “choke” is. This is a lever that is located on the dashboard of the car. In fact, it is designed to provide the engine with a richer air-fuel mixture during startup. You just need to pull it towards you, as a result of which the engine can run steadily in cold or rainy weather. After a few miles, the lever can be returned to its original position and allow the carburetor to do its job on its own. Information about the carburetor device can help those who want to clean it with their own hands. Now you know how the carburetor works and why it exists at all.
What is a carburetor in a car
The carburetor is a mandatory power unit of the internal combustion engine of cars and motorcycles. Until the end of the XX century, carburetors were installed on most cars, but these days they have been firmly superseded by more convenient and functional injector systems. Now they are often found in cars 20 or more years old. Let’s understand what a carburetor is, what changes it has undergone over a century of use and why it has given its place to injectors.
What is a carburetor
The need to develop an automatic device regulating the creation of air-fuel mixture arose at the end of the XIX century. Common earlier cars were powered by light gas, which is easy to ignite. However, such fuel was too expensive and inconvenient, so designers decided to switch to liquid analogues.
However, it needs to be mixed with air in special proportions for ignition. So the best engineering minds set out to develop a carburetor. The first model was presented by Luigi De Christoforis. It did not become widespread, but it became the basis for further developments.
Over the decades of further improvement, three basic varieties of carburetors were developed: diaphragm-needle, barbotage and float. However, in the second half of the XX century, the latter were used almost everywhere. In particular, they were installed on domestic cars until the 1990s.
What is a carburetor for?
The carburetor is needed to form an air-fuel mixture. Cars use gasoline, a liquid fuel that does not ignite properly from a spark ignition. If the fuel supply system is equipped with a carburetor (and in modern models – an injector), a fine fuel-air mixture enters the engine cylinders, which is easily ignited by a spark.
The emergence of carburetors in the late 19th century allowed the use of liquid fuel in automobiles, motorcycles, and other transport vehicles. In part, this determined the further development of the automobile industry and the idea of “a car in every home.” A century later, carburetors were superseded by more reliable and convenient injector systems.
Principle of operation of a carburetor
How a carburetor works using VAZ 2105 as an example: 1. Emulsion nozzle Economistat; 2. Emulsion channel Economistat; 3. Air nozzle main metering system; 4. Air nozzle Economistat; 5. Fuel nozzle Economistat; 6. Needle valve; 7. Float pin; 8. Ball stop needle; 9. Float; 10. Float chamber; 11. Main fuel nozzle; 12. Emulsion well; 13. Emulsion tube; 14. First chamber throttle axle; 15. Spool groove; 16. Spool; 17. large diffuser; 18. Small diffuser; 19. atomizer;
The carburetor prepares a combustible mixture of air and fuel and delivers it to the engine in the required proportions. The construction of the simplest carburetor consists of a float chamber and a mixing chamber connected to each other. A float regulates a constant fuel level in the first chamber. Fuel is transferred to the mixing chamber through the nozzle. As it passes through the atomizer it is broken up by the air jet and atomized and mixed with it. The result is an easily ignitable air-fuel mixture.
The design of a float carburetor includes:
- float and its shut-off needle (located in the float chamber);
- atomizer and Venturi tube (located in the mixing chamber);
- throttle valve.
Fuel flows from the tank to the float chamber through the fuel line. When the chamber is full, the float rises to the top and covers the supply with the needle. The jig is at the bottom of the chamber and dispenses the fuel transfer to the mixing chamber.
The mixing chamber contains a diffuser that cuts air around the atomizer. Thanks to this, the liquid is sucked into the chamber and atomized.
Read also : What is the difference between the injector and carburetor and which is better.
Why do you need a choke on a carburetor?
The design of the carburetor power system is supplemented by a throttle valve, which regulates the flow of air into the mixing chamber. Its position directly affects the amount of air-fuel mixture fed into the engine cylinders. Therefore, it is structurally linked to the gas pedal – when pressed, it supplies more air and fuel for active combustion and power generation.
Some carbureted cars were equipped with a choke control lever on the driver’s dashboard, which facilitated starting the car “in the cold. In the Russian-speaking community it was nicknamed the choke. In general, the word pretty well reflects the functional role of the lever. When the choke is pulled, the throttle damper is closed and the flow of air into the mixing chamber is restricted. Accordingly, the medium in it becomes more rarefied, and gasoline is drawn in at a greater volume. The result is an enriched mixture with a higher fuel content, which is excellent for starting the engine.
After the engine is started and warmed up to a sufficient temperature, the choke returns to its normal position and the choke is controlled in the same way again.
Typical carburetor malfunctions and their causes
- Difficulty starting engine in cold conditions:
- The choke does not close completely when the choke is pulled all the way down. The choke actuator needs to be adjusted.
- Throttle valve timing is not correctly adjusted.
- Slider clearance not correctly adjusted.
- Flap stays closed after starting. The problem is solved by cleaning or replacing the telescopic rod, diaphragm.
- The cause of malfunction most likely lies in high fuel level in the float chamber. It is necessary to adjust the float mechanism or replace the valve needle.
- The idle speed system is incorrectly adjusted.
- Nozzles clogged.
- Valve nozzle is clogged or wire is broken.
- Vacuum choke shutoff valve fails to operate at the proper moment.
- Excessive air is sucked in through the flange or hoses to the carburetor.
- The mixture is over-enriched due to poor float adjustment or leakage of the needle.
- The mixture is not enriched properly because the gas pedal pump nozzle is not properly sealed.
- The mixture is over-enriched or under-enriched due to clogged nozzles, sprayer, or fuel lines.
- Mixture is too lean due to small amount of fuel in float chamber, clogged nozzles, fuel passages.
- Secondary chamber does not start due to failure of pneumatic actuator.
Read also : What is a monoflash and how does it differ from a carburetor.
Pros and cons of the carburetor
Compared with the injector systems, the carburetor has a technically simpler design, and this is due to its main advantage – the low cost of repair. Many experienced drivers without problems fix the device on their own, using kits and parts, which are still found in the free sale. The more so that no special tools or skills are needed for repair. With a good instruction, even a beginner will quickly figure it out.
Mechanical carburetors keep working in contact with dirt and water (in moderate quantities, of course). Their penetration inside does not lead to failure or stop. However, this also has a disadvantage – the device has to be cleaned and adjusted regularly. Nevertheless, the increased resistance to harsh operating conditions compared to electronic carburetors or injectors is a fact.
Another valuable plus of the carburetor is its unpretentiousness to fuel quality.
In addition to the need for adjustment and cleaning, the carburetor has a disadvantage in the form of potential difficulties in operation in certain weather conditions. In particular, at minus temperatures, condensation freezes on its body. In hot weather, the device overheats and the engine output decreases due to fuel evaporation. Substitution of carburetors at the end of the XX century was due to the fact that they do not perform the distributed injection, as injector systems.