Air Injection: Description and Operation

Secondary Air Injection System Principle and Function

Principle

Due to the rich mixture during the cold start phase, the exhaust emissions contain an increased level of unburned hydrocarbons. Due to secondary air injection, exhaust in catalytic converter is reoxidized better and fewer pollutants are given off. The heat released by secondary oxidation shortens the start-up time of the catalytic converter considerably, as well as significantly improves emissions quality during the cold-running phase.

Function

In the cold-running phase, the engine control module activates the secondary air injection (AIR) pump via the secondary air injection (AIR) relay. The stream of air from the secondary air injection (AIR) pump opens the combination valve and allows air to flow into the exhaust system before the catalytic converter.