Principle and function

WARNING: This page is about a different car, the 2008 Audi RS 4 and 2007 Audi RS 4. However, it is still accessible from the selected car via links, so may be relevant.

Principle

Due to the rich mixture during the cold start phase, the exhaust emissions contain an increased level of unburned hydrocarbons. The Secondary Air Injection (AIR) system improves the secondary oxidation within the catalytic converter, thereby reducing harmful emissions. 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 start phase, the engine control module controls the Secondary Air Injection (AIR) pump via the pump relay. The stream of air from the Secondary Air Injection (AIR) pump opens the combination valves and allows air to flow into the exhaust system before the catalytic converter.