Principle and function
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-run phase, control modules - 3 - and - 4 - activate the secondary air injection pumps - 7 - and - 8 - via both secondary air injection pump relays - 2 - and - 5 -. The stream of air from the secondary air injection pump opens the combination valve and allows air to flow into the exhaust system before the catalytic converter.