Air Injection: Description and Operation

The secondary air system results in quicker heating and therefore earlier operating readiness of the catalytic converter following cold start.

Principle
Due to over-enrichment of the mixture during the cold start phase, there is an increased amount of un-combusted carbon monoxide in the exhaust. Secondary Air Injection (AIR) improves secondary oxidation in the catalytic converter and therefore reduces emissions. The heat produced by secondary oxidation greatly reduces start - up time for the catalytic converter, therefore improving exhaust quality during the cold start phase significantly.

Function
- In the cold start phase, the ECM -2- activates the secondary air pump - 12 - via the relay for secondary air pump -1- . Air reaches the combination valve for Secondary Air Injection (AIR) - 10-.
- Parallel to this, the Secondary Air Injection (AIR) solenoid valve -3- is activated, which permits negative pressure to reach the combination valve for Secondary Air Injection (AIR) - 10 - and the pressure unit for boost pressure regulation -7- . The combination valve for Secondary Air Injection (AIR) thereby opens the path for secondary air to the exhaust channels of the cylinder head.
- To prevent unnecessary torque loss, secondary air is led around the turbocharger -8- . For this, the boost pressure regulation pressure unit opens the boost pressure valve. The pressure unit, designed as a double reservoir, has a vacuum connection for this on the low pressure side.

1 - Secondary Air Injection (AIR) pump relay - J299 -
2 - Motronic Engine Control Module (ECM) - J220 -
3 - Secondary Air Injection (AIR) solenoid valve - N112 -
4 - Intake manifold
5 - Check-valve
- Installed position (light/dark half): Arrow points in direction of flow, as shown in figure
6 - Vacuum reservoir
7 - Pressure unit for boost pressure regulation
8 - Turbocharger
9 - Cylinder head
10 - Combination valve for Secondary Air Injection (AIR)
11 - Air filter
12 - Secondary Air Injection (AIR) pump motor - V101 -