Air Injection System
A vehicle engine requires the right amount of fuel and air mixture to run efficiently. Traditionally, the carburetor was used to control the fuel-air mixture. The air injection system was invented to address the weaknesses of the carburetor such as unequal supply of fuel/air mixture to cylinders. Air injection, also known as secondary air injection, is an emission control system that injects fresh air into a stream of exhaust gases to enable more complete combustion.
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As the exhaust gases leave the engine, they may contain unburned gases and partially burnt fuel. The air contains oxygen which burns unburned fuel and gases. Ideally, the fresh air dilutes the exhaust gases and reduces carbon and hydrocarbon emissions.
The major part of the air injection system includes the air pump, air distribution manifold, air check valve and diverter pump.
Air pump is a belt driven pump that forces low pressure air into the system.
The work of this valve is to prevent air from flowing into the exhaust system when the vehicle is decelerating. It, therefore, preventing backfiring. Diverter valve also limits maximum air pressure in the system by releasing excess pressure through a muffler or silencer.
Air Distribution Manifold
The function of the air distribution manifold is to direct air into the exhaust valve.
Air Check Valve
The air check valve prevents exhaust gases from entering the air injection system. It is located between the air distribution manifold and a diverter valve.
How it works
When the engine is in operation, the air pump vanes spin and push air into the diverter valve. When not decelerating, the air is forced into the engine through a check valve, diverter valve and the air injection valve. However, during a long period of deceleration, the diverter valve prevents air from flowing onto the exhaust manifold. This prevents potential backfires and hence protects the exhaust system from damage. The diverter valve releases excess pressure from the system when need be.
There are two implementation methods for air injection, the pumped air injection and the aspirated air injection.
Pumped air injection
This system uses an air pump that uses an electric motor or belt to turn. The intake air of the pump is passed through air filters, which removes dirt particles. Air is transmitted to the injection point with little pressure. A check valve prevents exhaust from flowing back to the air injection system because it would destroy engine components.
Aspirated air injection
In this system an air injection pump draw clean air from the air filter. An aspirator valve is placed in the pipe. When the engine is idle, the exhaust system draws air into the catalytic converter exhaust stream through aspirator valve.
It is prudent to take good care of the air injection system as it means the difference between a proper functioning engine and a poor one. It is imperative that you contact your mechanic for evaluation. You should replace the system immediately if need be.
Read more about your car’s emission system: