The exhaust emissions are operated by mechanism which is control dependent on the method of injection and the point at which air enters the exhaust system and can also vary during the course of the development of the technology.The Air injection is implemented in two ways Pumped air injection and Aspirated air injection.
The first system used to inject the air very close to the engine, either in the cylinder head’s exhaust ports or inside exhaust manifold. These systems provided the oxygen to oxidize and burned the partially burned fuel inside the exhaust before it’s ejected out of the tail pipe.There was always some significant amount unburned and partially burned fuel in the exhaust during the 1960s and early 1970s vehicle so therefore air injection came into quite a use at those times. The emission control strategies have grownmore and more sophisticated and efficient and the amount of partially burned fuel is reduced to quite an amount particularly when the catalytic converter was introduced, the function of the air injection was shifted. Rather than its previous function it was used to support the catalytic converter. The original air injection point is now known as the upstream injection point.
When the engine is cold, air rushes into it at this point and cleans up the extra – rich exhaust thereby, increasing the temperature inside the exhaust which is beneficial for the catalytic converter. Once the engine gets warm the air is injected to the downstream location, i.e., the catalytic converter itself which assists with the catalysis of unburned hydrocarbons and carbon monoxide.