Exploring the Different Types of Carburetor

You will rarely find an online source where all the different types of carburetors are pooled together. Most of the sources don’t even understand the proper differentiation. And the presentation of some makes things even more confusing.

That’s why taking matters into our own hands; we have listed the different types of carburetors. We have also included a little description. It was in our capability to write way more than we have here. But that would have made the article absurdly long.

In the following section, you have the list of the types of carburetors. If you are checking for a particular type of carburetor, then remember that a carburetor can have many names.

We have mentioned all of them in the description. If you don’t find your carburetor in the list, try using your browser’s search option.

Type of carburetors

We don’t want you to get confused. So that’s why we grouped all of the carburetors in specific, well-defined categories.

A particular type will never be redundant with a carburetor of the same group. But it could be similar to other types of other groups to some degree.

Types based on venturi

  1. Fixed venturi carburetor / constant choke carburetor
    1. Plain venturi /single venturi
    1. Double venturi
    1. Triple venturi
    1. Vane venturi
    1. Nozzle-bar venturi
  2. Variable

Types based on the direction of airflow

  1. Downdraft
  2. Side draft
  3. Updraft
  4. Semi-down draft

Types based on the arrangement of the float chamber

  1. Eccentric
  2. Concentric

Types based on the number of barrels

  1. Single barrel
  2. Dual barrel
  3. Four barrel

Types based on the powering system

  1. Manually operated carburetor
  2. Vacuum controlled carburetor

Types based on metering systems

  1. Air-bleed jet carburetors
  2. Metering rod carburetors

There are some carburetor types that didn’t fall in any of the groups above. But we can’t leave them. We have a separate section where we describe all of these-

  1. Multijet carburetor
  2. Catalytic carburetor
  3. Manual choke carburetor
  4. Float control carburetor

Now time for the nerdy part. You will find a clear description of all the types below.

Carburetor Types Based on the Venturi

This is one of the most popular classification categories of carburetors. But most of the sources online give you a blatantly wrong idea about the mechanics of the individual types.

They can’t even separate the different types accurately. And yeah, venturi types and barrel types are not the same. Venturi is a part of the barrel which can have different types.

Those types are divided primarily into the following two-

  1. Fixed venturi carburetor
  2. Variable venturi carburetor

1. Fixed venturi carburetor

The type of carburetors where the size of the venturi does not change and fuel flow is controlled by the airflow of the venturi are called fixed venturi carburetors.

Constant choke carburetor is another name for these. Don’t mess it up with plain venturi carburetor because that is another subtype of the fixed venturi carburetor.

Those sub types are-

  1. Plain venturi
    • Double venturi
    • Triple venturi
    • Vane venturi
    • Nozzle-bar venturi

Many might ask that why I include them as a subtype of the fixed venturi, whereas everyone else has made it a separate category.

That is because they are directly related to the venturi style and fall under the definition of fixed venturi type carburetor. That means one can’t be one of these five types without being a fixed venturi carb.

Some might also categorize double and triple venturi types as a main category by calling them multi-venturi carburetors. Moreover, I also think that is absolutely unnecessary because there aren’t more than those two types.

Now let’s get to our definitions-

1. Plain venturi carburetor

This venturi has a clear path inside the venturi for airflow. Here the fuel flow is controlled by the varying velocity of the airflow like all other fixed venturi carbs.

It is also knowns as a single venturi carburetor.

  • Double venturi carburetor

These types of carburetors have two venturi for a greater air velocity. Along with the main venturi, there is also the boost venturi. As I said before, this can also be called a multi-venturi carburetor.

  • Triple venturi carburetor

This is an extension of the double venturi type with one additional venturi. You have the main, primary, and secondary venturi here. This can also be called a multi-venturi carburetor.

  • Vane venturi carburetor

In this kind of carburetor, there is a vane or blade attached to a rotating axis that can be pushed by the incoming air. The blade or vane changes the venturi area along with the opening of the throttle valve. Hence, giving you better control over the air-fuel ratio by altering the vacuum in the venturi.

  • Nozzle-bar venturi

This is a plain or single venturi carburetor with a fuel jet nozzle attached to it. This nozzle sprays fuel particles into the air coming from the inlet manifold. The mixture of fuel also depends on the opening of the throttle. It gives you a homogenous air-fuel ratio.

2. Variable venturi carburetor

The carburetors that can change the size of the venturi are called variable venturi carburetors. These carburetors change their air-fuel mixture by controlling the size of the venturi.

It is also known as constant velocity, constant depression, constant vacuum, and variable choke carburetor.

There is generally a piston with a needle jet that is attached to a spring. With the spring, you will be able to control the area of the venturi and thus control the fuel mixture.

Carburetor Types Based on the Direction of Air Flow

This is another popular category of classification. This just tells you which direction the air is flowing respectively to the fuel nozzle.

  1. Downdraft
  2. Side draft
  3. Up-draft
  4. Semi-down draft

1. Downdraft carburetor

In this carburetor, the fuel discharge nozzle faces opposite to the airflow. You can also say that the air comes from the top of the carburetor and exits from the bottom since the direction of the nozzle is considered up. Therefore, this unit can produce higher volumetric efficiency.

2. Side draft carburetor

In this carburetor, the fuel discharge nozzle is in a horizontal direction. You can also say the air comes from one side of the carburetor and exits from another. It is also called a cross-draught carburetor. This type reduces the resistance of airflow

3. Up-draft carburetor

In this carburetor, the fuel discharge nozzle faces the same direction as the airflow. You can also say the air comes from the bottom of the carburetor and exits from the top respective to the nozzle. These are not used that much.

4. Semi-down draft carburetor

In this carburetor, the fuel discharge nozzle faces opposite to the airflow at an angle. You can also say that the direction of the airflow is inclined from top to bottom. This engine achieves the benefits of both side draft and downdraft carburetors.

Carburetor Types Based on the Arrangement of Float Chamber

This classification is based on the position of the float chamber. It is more relevant to the mechanics and manufacturers.

  1. Eccentric carburetor
  2. Concentric carburetor

Here are their details-

1. Eccentric

The carburetors that have float chambers placed at a side of the venturi tube are called eccentric carburetors.

Here, the fuel is coming into the venturi from only one direction. That’s why when the vehicle is tilted, the fuel-air mixture can increase or decrease depending on the direction of tilt. This reduces accuracy. It can happen while ascending or descending a hill or flyover.

2. Concentric

The carburetors that have float chambers placed around the venturi tube are called concentric carburetors.

This carburetor design doesn’t have any problems of the eccentric type as the fuel is coming into the venturi from multiple sides.

Carburetor Types Based on the Number of Barrels

The basic differentiation doesn’t have much to explain. The types are just based on the number of barrels the carburetors have-

  1. Single barrel
  2. Dual barrel
  3. Four barrel

However, I will describe some interesting facts about the types that you might wanna know.

1. Single barrel carburetor

It is just a carburetor with a single tube.

2. Dual barrel carburetor

These carburetors have two barrels with separate fuel jets, idling systems, throttle, and chokes. However, each barrel might have multiple float chambers. Both of the barrels will have the same circuitry, but they could move separately according to the throttle.

It generally comes with eight or more cylinder engines to provide a better fuel mixture. You might also call them a 2-stroke carburetor or multi-barrel carburetor.

3. Four barrel carburetor

It is just two dual carburetors in one unit. The primary side has a choke, an accelerating pump metering, and idle systems. The secondary unit has its own float bowl. The two sets of barrels can work together or separately. They can also be controlled manually.

Carburetor Types Based on the Powering System

This classification is based on how the fuel mixture is controlled. The two types are-

  1. Manually operated
  2. Vacuum operated

Although the difference is small, it plays a big role when choosing your carburetor.

1. Manually operated

The carburetors that have a mechanical linkage between the power jets and throttle shaft for manual control of the fuel composition are manually operated carburetors. This type of carburetors is only for experienced people.

2. Vacuum operated carburetors

These are the common carburetors that use vacuum-controlled power jets for controlling the fuel mixture. For average cars, this gives the most accurate performance.

Carburetor Types Based on the Pressure above the Fuel

This is a crucial separation of carburetors that you need to know to understand the mechanics of your carb. They are-

  1. Unbalanced carburetors
  2. Balanced carburetors

It talks about the balance of fuel pressure

1. Unbalanced carburetors

The carburetors where the pressure above fuel changes with the atmospheric pressure are called unbalanced carburetors.

2. Balanced carburetors

The carburetors where the pressure above the fuel are equal to the air intake in the air horn are called a balanced carburetor. It contains a balance tube that connects the float chamber to the air horn.

Carburetor Types Based on Metering Systems

This might be the toughest group to understand as you need to have a clear idea about the inner mechanics of a carburetor. Fortunately, it only has two types

  1. Air-bleed jet carburetors
  2. Metering rod carburetors

Understanding these two is really important if you are going to buy a new carburetor.

1. Air-bleed jet carburetors

These carburetors use a metering jet to transfer the fuel to the main discharge nozzle. Here the vent tube is connected to the main discharge nozzle. The fuel is mixed with the air while it is drawn to the venturi. Increasing suction will also increase the amount of air-fuel mixture.

2. Metering rod carburetors

These carburetors use a metering rod to control the amount of fuel. This metering rod extends into the jet, and it controls the fuel with the opening and closing of each of its steps.

You can control the fuel with the throttle shaft. The rod is raised when the throttle valve is opened and vice-versa. When it is open, the throttle valve allows more space so that more fuel can pass.

Some more types

The types below didn’t fall into any significant category of carburetors. That’s why we are describing them in this separate section.

Multi-jet carburetor

These types of carburetors have multiple jets for fuel injection at different speeds of the engine.

Catalytic carburetors

These types of carburetors are made with special metals like platinum or nickel to break down the diel to its elemental components so that it can have a more homogeneous mix of air and fuel.

Manual choke carburetor

The chokes of these carburetors can be controlled manually. But they are generally not used with cars. They are more common with aircraft.

Float control carburetor

These are common with motorbikes. They will allow you to manually depress the float so that you can fill the fuel chamber inside along with the carburetor. But they can be a fire hazard.

Conclusion

I don’t think there are any other types left. And looking at the current trend of the automotive industry, there might not be many new types of carburetors any time soon.

So, I can surely say you have all the different types of carburetors here.

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