The carburetor is called the ‘Heart’ of the automobile, and it cannot be expected that the engine will act right, give the proper horsepower, or run smoothly if its ‘heart’ is not performing its functions properly.
What is a carburetor?
A carburetor also spelled carburettor, is a device for supplying a spark-ignition engine with a mixture of fuel and air. Components of carburetors usually include a storage chamber for liquid fuel, a choke, an idling (or slow-running) jet, the main jet, a venturi-shaped air-flow restriction, and an accelerator pump.
Carburetors add fuel to air to make a mixture that’s just right for burning in the cylinders. Modern car cylinders are fed more efficiently by fuel-injection systems, which use less fuel and make less pollution.
But you’ll still find carburetors on older car and motorcycle engines and in the compact engines in lawnmowers and chainsaws.
Gasoline engines are designed to take in exactly the right amount of air so the fuel burns properly, whether the engine is starting from cold or running hot at top speed.
Getting the fuel-air mixture just right is the job of a clever mechanical gadget called a carburetor: a tube that allows air and fuel into the engine through valves, mixing them together in different amounts to suit a wide range of different driving conditions.
You might think “carburetor” is quite a weird word, but it comes from the verb “carburet.” That’s a chemical term meaning to enrich a gas by combining it with carbon or hydrocarbons. So, technically, a carburetor is a device that saturates air (the gas) with fuel (the hydrocarbon).
Who invented the carburetor?
The first carburetor was invented by Samuel Morey in 1826. The first person to patent a carburetor for use in a petroleum engine was Siegfried Marcus with his 6 July 1872 patent for a device that mixes fuel with air.
A very simplified diagram of Karl Benz’s original carburetor from his 1888 patent. Fuel from the tank enters what he called the generator underneath, where it evaporates.
The fuel vapor passes up through the gray pipe and meets air coming down the same pipe, which enters from the atmosphere through perforations at the top. The air and fuel mix in the chamber then passes through a valve into the cylinder, where they burn to make power.
Parts of Carburetor
The following are the Parts of the Carburetor:
- Throttle Valve
- Metering system
- Idling system
- Float Chamber
- Mixing Chamber
- Idle and Transfer port
- Choke Valve
- Throttle Valve: It is a valve designed to regulate the supply of a fluid as steam or gas and air to an engine and operated by a handwheel, a lever, or automatically by a governor especially.
- Strainer: It is a device that is used to filter the fuel before entering the float chamber. It consists of a fine wire mesh that filters the fuel and removes dust and other suspended particles from it. These particles if not removed can cause blockage of the nozzle.
- Venturi: The air passes through a narrowed neck inside the carburetor called a venturi, which speeds up its flow at that point. As air flows faster its pressure drops, so there is a slight vacuum inside the venturi. The fuel jet opens into the venturi, and the partial vacuum sucks fuel through the jet into the air stream.
- Metering system: The fuel discharge nozzle is located in the carburetor barrel so that its open end is in the throat or narrowest part of the venturi. It is this pressure difference, or metering force, that causes fuel to flow from the discharge nozzle.
- Idling system: It provides the air-fuel mixture at speeds below approximately 800 rpm or 20 mph When the engine is idling, the throttle is almost closed Air flow through the air horn is restricted to produce enough vacuum in the venturi.
- Float Chamber: A float chamber is a device for automatically regulating the supply of a liquid to a system. It is most typically found in the carburetor of an internal combustion engine, where it automatically meters the fuel supply to the engine.
- Mixing Chamber: In the mixing chamber, the mixture of air + fuel occurred. And then supplied to the engine cylinder.
- Idle and Transfer port: In addition to the main nozzle in the venturi portion of the carburetor, two other nozzles, or ports, deliver fuel to the engine cylinder.
- Choke Valve: A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine.
How does a carburetor work?
A carburetor relies on the vacuum created by the engine to draw air and fuel into the cylinders. The throttle can open and close, allowing either more or less air to enter the engine. This air moves through a narrow opening called a venturi. This creates the vacuum required to keep the engine running.
Carburetors vary quite a bit in design and complexity. The simplest possible one is essentially a large vertical air pipe above the engine cylinders with a horizontal fuel pipe joined onto one side.
As the air flows down the pipe, it has to pass through a narrow kink in the middle, which makes it speed up and causes its pressure to fall.
This kinked section is called a venturi. The falling pressure of the air creates a sucking effect that draws air in through the fuel pipe at the side.
When a fluid flows into a narrower space, its speed increases but its pressure drops. This explains why wind whistles between buildings and why canal boats, drifting parallel to one another, are often pushed together.
It’s an example of the law of conservation of energy: if the pressure didn’t drop, the fluid would be gaining extra energy as it flowed into the narrow section, which would violate one of the most basic laws of physics.
here’s how Carburetor works:
- Air flows into the top of the carburetor from the car’s air intake, passing through a filter that cleans it of debris.
- When the engine is first started, the choke can be set so it almost blocks the top of the pipe to reduce the amount of air coming in (increasing the fuel content of the mixture entering the cylinders).
- In the center of the tube, the air is forced through a narrow kink called a venturi. This makes it speed up and causes its pressure to drop.
- The drop in air pressure creates suction on the fuel pipe, drawing in fuel.
- The throttle is a valve that swivels to open or close the pipe. When the throttle is open, more air and fuel flow to the cylinders so the engine produces more power and the car goes faster.
- The mixture of air and fuel flows down into the cylinders.
- Fuel is supplied from a mini-fuel tank called the float-feed chamber.
- As the fuel level falls, afloat in the chamber falls and opens a valve at the top.
- When the valve opens, more fuel flows in to replenish the chamber from the main gas tank. This makes the float rise and closes the valve again.
Types of Carburetor
There are three types of carburetors:
- Up-draft carburetors
- Horizontal type carburetors
- Down-draft type carburetors
Up-draft type carburetors
An updraft carburetor is a type of carburetor a component of engines that mix air and fuel together in which the air enters at the bottom and exits at the top to go to the engine.
An updraft carburetor was the first type of carburetor in common use. In an updraft carburetor, the air flows upward into the venturi according to Edward Abdo in Power Equipment Engine Technology. Other types are downdraft and side-draft carburetors. An updraft carburetor may need a drip collector.
This carburetor operates with lower air velocities and larger passages. This is because gravity assists the air-fuel mixture flow to the cylinder.
The downdraft carburetor can provide large volumes of fuel when needed for high-speed and high-power output.
In this type of carburetor air comes from the top of the mixing chamber, and the fuel comes from the bottom of the mixing chamber, here also the same principle works, due to low pressure created by the two venturis fuel comes out through the pipe and then the mixing of fuel and air occurred here.
Horizontal Type Carburetors
This type of carburetor is used when we have the constraint of space for assembly. In horizontal or side draught carburetor, as the name suggests, the jet tube is placed in a horizontal direction. One more advantage of this type of carburetor is that it reduces the resistance of the flow due to the absence of the right-angle mechanism in the intake area.
The working principle of this type of carburetor is very simple. Here the carburetor stays in the horizontal position where the air is coming in through one end of the carburetor shown in the below figure. And mixed with fuel to make the air-fuel mixture and then the air-fuel mixture is going to the engine cylinder for combustion.
How To Clean A Carburetor?
Check your Owner’s Manual before cleaning the carburetor. Always follow the manufacturer’s complete instructions for cleaning and maintenance. Make sure the carburetor is cool to the touch before cleaning.
- Dilute cleaner: In a large container mix dilute cleaner, However, it’s important to use a non-corrosive cleaner that doesn’t harm or degrade any plastic or rubber pieces on the carburetor. You should avoid using vinegar because the acetic acid makes metal susceptible to rust. Additionally, bleach should never be used, because sodium hypochlorite (bleach) will corrode metals such as steel and aluminum, and degrade rubberized seals.
- Clear air filter: Before cleaning your carburetor, check the air filter to make sure that the air coming into the carburetor is clean and free of blockage, which can result in black smoke emissions from the exhaust. Shut off the fuel supply and disconnect the spark plug wire, if one exists. Remove the housing and the wing nut attaching the filter, and remove the outer element. Use a can of compressed air to remove debris.
- Remove the carburetor: Remove any covering plate or shield, as well as linkage and hoses using pliers and a screwdriver, where necessary. Also, remove any cover or clamps holding the carburetor in place, and remove the hose clamp that connects it to the fuel line. And remove the carburetor, and use compressed air to blow off any excess dirt on the outside casing. (Note: if unfamiliar with this procedure, consult with a professional before cleaning.)
- Remove carburetor float: Remove the bolt holding the carburetor float (bowl-shaped container) in place, being careful not to spill any remaining gas inside the float (dispose of this securely). This is a common point of varnish buildup on carburetors. Also, remove the pin that the float pivots on, and place it aside in a safe spot. Now pull the float straight out of its casing.
- Remove other removable components: Note the location and placement of any other carburetor components you’re removing to allow cleaning access.
- Soak and scrub components: Submerge the carburetor float and other components in a large container with your dilute cleaner, and soak thoroughly for 10 minutes. Use a brass brush to scrub all metal components, and a stiff nylon brush to scrub plastic pieces. Make sure the tiny vents get cleaned. Clean the small parts in the cleaning solution as well.
- Rinse and dry: Rinse all carburetor components in a bucket of clean water, and allow to air dry completely. For small holes and vents, use a can of compressed air to remove any excess moisture.
- Reassemble and replace: Carefully reassemble the carburetors, and mount them to the engine. Re-link all hoses, clamps, and wires.
Functions of carburetors:
The main functions of carburetors are
- The main function of carburetors to mix air and gasoline and provides a high combustion mixture.
- It controls the engine speed.
- It also regulates the air-fuel ratio.
- Increase or decrease the amount of mixture according to the engine speed and load changes.
- To keep a certain head of fuel in the float chamber all the time.
- Vaporize the fuel and mix to air to a homogeneous air-fuel mixture.
- To supply the correct amount of air-fuel mixture at the correct strength under all conditions of load and speed of the engine.
Advantages of the carburetor:
- Carburetor parts are not as expensive as that fuel injectors.
- With the use of a carburetor, you get more air and fuel mixture.
- In terms of road tests, carburetors have more power and precision.
- Carburetors are not restricted by the amount of gas pumped from the fuel tank which means that cylinders may pull more fuel through the carburetor which would lead to a denser mixture in the chamber and greater power as well.
Disadvantages of the carburetor:
- At very low speeds, the mixture supplied by a carburetor is so weak that, it will not ignite properly and for its enrichment, at such conditions, some arrangement in the carburetor is required.
- The working of a carburetor is affected by changes in atmospheric pressure.
- More fuels are consumed since carburetors are heavier than fuel injectors.
- More air emissions than fuel injectors.
- The maintenance costs of a carburetor are higher than the fuel injection system.
Applications of Carburetor:
- Used for Spark-Ignition Engine.
- It is used to control the speed of the vehicles.
- It converts the main fuel petrol into fine droplets and mixes with air to burn in smoothly and properly without any problem.
A carburetor’s job is to supply an internal combustion engine with air/fuel mixture. Carburetors regulate the flow of air through their Main bore (Venturi), this flowing air draws in fuel and the mixture enters the engine via the intake valve.
Fuel injection systems eventually replaced carburetors because they could be better controlled, which provided more efficient fuel use, lesser pollution, and lesser fuel consumption as well. Power and performance were the main reasons why fuel injection systems began to replace the carburetor starting in 1970.
Here are four telltale signs that your carburetor needs attention.
1. It just won’t start.
2. It’s running lean.
3. It’s running rich.
4. It’s flooded.
So if it develops any sort of issue, it can throw off this mixture and affect the engine performance. A bad carburetor may result in an engine with sluggish acceleration and a noticeable reduction in power and fuel efficiency.
A carburetor that flows more air doesn’t necessarily use more gas. In fact, given the same engine, a carb rated at a higher cfm number often needs larger fuel jets than does a smaller carb to deliver the same air/fuel ratio.