Cars Simplified

Air Injection System

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The air injection system is an early emissions system that would aid the catalytic converter in its task of breaking down the environmentally harmful gasses that Combustion generates in an engine. Since a catalytic converter needs oxygen to catalyze the engine emissions, air can be injected to supply extra oxygen.

Why Air Injection Was Phased Out

As ECUs became more advanced and able to more finely control fuel injectors, oxygen sensors were placed before and after the catalytic converter to monitor the effectiveness of controlled lean cycles, allowing the engine to leave some oxygen after the combustion process some of the time, which eliminated the need for a dedicated air injection system while being more fuel efficent.