General Information

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 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 ECM - 3 - activates the secondary air pump - 1 - via the relay for secondary air pump - 2 -. Air reaches the combination valves for Secondary Air Injection - 4 - and - 8 -.

• The Secondary Air Injection valve - 5 - is activated in parallel, which allows the vacuum to reach the combination valves for Secondary Air Injection - 4 - and - 8 -. The appropriate combination valve for Secondary Air Injection thereby opens the path for secondary air to the exhaust channels of the cylinder head.