Mechanical Basics

# What Is Air-Fuel Mixture And Types Of Air-Fuel Mixture?

Apr 5, 2021

## What Is Air-Fuel Mixture?

Air-Fuel Mixture is the combination of the air and fuel (the fuel will be petrol in maximum cases) in a specific ratio that will help the engine to work properly. Every petrol engine will suck the air-fuel mixture for its suction process and the mixture will burn (or combust) using the sparks which result in the combustion process.

To mix the air and fuel in the required ratio, the bike or motorcycle takes the help of a Carburetor.

## Types Of Air-Fuel Mixtures:

Engines will not work under the same conditions throughout the process. Sometimes, the engine will be run at slow conditions, sometimes at high and medium so, the speed of the engine will depend upon the air and fuel mixture input. So, the types of air-fuel mixture depend upon the types of speeds that the engine will be run.

The types of engine speeds will be classified as low, normal, and high speeds; according to it, the types of air-fuel mixtures will be

• Lean Mixture
• Stoichiometric Mixture and
• Rich Mixture

### Stoichiometric Mixture:

The Stoichiometric Mixture has a mixture figure of 15:1. It does mean that the engine consumes 15 parts of Air and 1 part of Fuel (petrol) for its starting. The stoichiometry mixture is the mixture that requires a normal speed of bike or motorcycle.

We can even prescribe the explain that if an engine requires to run at the economy stage then the throttle valve will allow the air-fuel mixture of around 15:1.

### Lean Mixture:

The Lean mixture is the mixture that the engine will consume less air-fuel ratio and runs at low speed. The air-fuel mixture will be around 12:1 which means the 12 parts of air are mixed with 1 part of fuel (petrol).

If we compare the lean mixture with the stoichiometric mixture then we can that the stoichiometric mixture consumes more fuel.

### Rich Mixture:

Now, talking about the rich mixture, as the name indicates, the engine will consume more fuel and air for its working. The air-fuel mixture will be appropriately around 17:1.

If we observe carefully, the rich mixture will be used at high speeds. As the speed is high, the consumption of the air and fuel mixture is also high. If we observe carefully, the fuel consumption in the rich mixture will be high compared to the stoichiometric mixture and lean mixture.

For example: If the car or bike is required to climb the high elevations on the roads then the normal speed will not be required to overcome the height instead, the car or bike will go back.

So, to overcome the high elevations it is necessary to increase the engine speed which may require accelerating more and consumption of fuel increases.

We can say that the mixture ratio will be increased as the acceleration increasing and the increased ratio is called as the Rich Mixture.

## Conclusion:

The type of mixture will depend upon the engine speed and situation of the engine running. Sometimes, the engine will be at low speed but require climbing the wedge and elevating areas and roads that need high acceleration and a rich mixture will help it to overcome.

There are only three types of air-fuel mixture that are normalized according to the standards of the engine. The air and fuel mixture may vary slightly from one type of engine to another type of engine.

There are three types of Air-Fuel Mixture, they are as follow:

• Stoichiometric Mixtures
• Rich Mixtures
• Lean Mixtures

The Rich Mixture is a type of air-fuel mixture that engine will consume more fuel quantity than air. So, the ratio of the air-fuel in rich mixture will be around and above 17:1.

The Lean Mixture is a type of air-fuel mixture that engine will consume the less fuel quantity than air. So, the ratio of the air-fuel in lean mixture will be around and below 12:1.

The Stoichiometric Mixture is another type of air-fuel mixture that engine will consume the fuel and air quantity at normal speeds. So, the ratio of the air-fuel in stoichiometric mixture will be around 15:1.

At high speeds, the engine consumes high fuel quantity than the air so, the type of mixture that uses high fuel quantity than air is Rich Mixture. The air-fuel ratio at high speeds or the air-fuel ratio of rich mixture will be 17:1.

The Choke Valve is the valve that is used to allow or restrict the air flow into the carburetor. The choke valve is a manual device that used according to the situation of the engine.