Carburettor: Components, Functions and Working Mechanism

A carburettor is an essential mechanism responsible for the engine combustion process. The function of a carburettor is to pass the pressure of air and fuel mixture to create pressure inside the engine.

For its optimum performance, the car engine runs smoothly. However, there are different aspects involved in a carburettor. To know more about them, follow the next segment that discusses what a carburettor is.

A carburettor is situated between the induction manifold and the fuel filter. It is a device that supplies spark ignition to the engine by a mixture of fuel and air. This air and oil mixture is also known as a combustible mixture.

A carburettor has different parts working together, which are made with different materials. For example, the main part of the venturi is made with lightweight aluminium. However, the other moving parts are made with stainless steel.

The functions of a carburettor are as follows:

• The primary function of a carburettor is to mix air and fuel to make a combustion mixture.
• A carburettor is responsible for engine speed.
• A carburettor controls the proportion of air and fuel in different engine situations.
• It keeps a certain amount of fluid always floating in chambers.
• It controls the ratio of air and fluid.
• It vapourises the oil or gasoline to make a homogeneous mixture of air and fuel.

The functions of a carburettor are as follows:

• The primary function of a carburettor is to mix air and fuel to make a combustion mixture.
• A carburettor is responsible for engine speed.
• A carburettor controls the proportion of air and fuel in different engine situations.
• It keeps a certain amount of fluid always floating in chambers.
• It controls the ratio of air and fluid.
• It vapourises the oil or gasoline to make a homogeneous mixture of air and fuel.

The components of a carburettor are as follows -

1. Venturi

Venturi is a pipe-like structure that passes the air and fuel mixture. The velocity of fuel goes maximum in the narrow portion of this pipe. There are 6 types of venturi. They are:

• Variable carburettor venturi
• Single carburettor or plain venturi
• Double carburettor venturi
• Tripple carburettor venturi
• Vane venturi
• Nozzle bar carburettor venturi

2. Throttle Valve

It acts significantly for a carburetted engine as it regulates how much combustion mixture should enter the cylinder. Vehicles have different types of throttle valves; for example:

• Electromotive throttle actuators
• Electronic throttle actuators
• Air management valves
• Air flap servo motors, etc.

3. Choke

A choke works on the pressure of the intake manifold; therefore, it regulates the proportion of fuel in the combustion mixture. It stays in an open position, but when it comes to controlling the airflow, it rotates and forms an angle to perform the task.

A carburettor choke can be of 3 types. These are:

• Electric choke
• Divorced choke
• Hot-air choke

4. Float Chamber

It is a storage chamber that supplies fuel continuously. The amount of fuel in this chamber is controlled by a float valve. The float moves downwards with decreasing fuel in the float chamber while it moves upwards when fluid increases.

5. Mixing Chamber

As the name suggests, in this chamber, the air and fuel get mixed and turn into a combustion mixture. The main function of a carburettor is to mix air and fuel; therefore, this chamber is of utmost importance. The ideal combustion mixture has 15 parts of air and 1 part of fuel.

6. Metering System

This system is responsible for controlling fuel flow into the nozzle. This system controls the fluid quality and takes care of fuel discharge. The two main parts of the metering system are -

• Metering orifice
• Fuel discharge nozzle

7. Idling System

The idling system consists of a passage that connects the venturi with the float chamber. The system obtains enough metering forces at low air pressure in an idling position. The fuel passes through this idle passage by pulling the throttle valve and body.

8. Strainer

This device refines the fuel before it enters the float chamber. This strainer is made with fine wire that strains all the fuel's dust particles and other impurities.

Having said that, individuals should note that modern carburettors have three additional parts.

9. Throttle Return Check

In an engine running at high speed, sometimes the total throttle rises very high, which results in a manifold vacuum of high intake. Further, during  v/v  (volume/volume)overlap, this action draws exhaust into the engine intake.

Therefore, it may lead to misfiring and engine stalling. Thus, in modern carburettors, a throttle return check  v/v is fixed to the throttle linkage to prevent this trouble.

10. Anti-Dieseling Solenoid

Modern vehicles with emission control systems get hotter very quickly. Therefore, it produces hot spots in different parts of the combustion chamber, which further leads to pre-ignition. Anti-dieseling solenoid technique prevents this unnecessary pre-ignition in engines that are harmful to engine functionality.

11. Automatic Mixture Control

In this system, there is a valve of plunger shape in between solenoid and spring. This valve controls the working of a separate jet inside the float chamber. As the solenoid turns on, it lifts the v/v upwards, leading to an increased jet fuel supply. Similarly, when the solenoid turns off, the valve goes downwards and decreases fuel supply.

This solenoid is excellently monitored by a computer that gets signals from coolant temperatures, engine speed etc. therefore, it is an advanced type of carburettor that controls mixture efficiently with high technology.

The working process of a carburettor is as follows:

Step 1: From the air intake of cars, airflow comes into the top of the carburettor by passing through a filter.

Step 2: After a certain intake of air, a choke valve blocks the further intake.

Step 3: The air passes through the narrow section of venturi, the velocity increases and creates a low-pressure pocket.

Step 4: As the air pressure drops, fuel comes from the fuel chambers.

Step 5: The fuel consumption is regulated by the throttle valve.

Step 6: Fuel and air get mixed and come into the cylinder.

Step 7: The fuel supply remains intact as the float chamber continues to supply it.

Step 8: Gradually, fuel pressure drops, and the valve at the top opens.

Step 9: As the combustion mixture enters the cylinder, it sends spark ignition to the engine.

Step 10: As combustion happens, the whole process starts repeating again

Therefore, we hope this piece will give you a comprehensive idea of what a carburettor is, its working and different components. The system is helpful for engine ignition and is quite cheap too. In addition, it is easily replaceable.

However, modern-day vehicles have the advanced form of a carburettor and fuel injection. It also serves the same purpose but more efficiently.