Secondary Air System, Components and Function

Secondary Air System, Components And Function

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

Principle
Due to over-enrichment of the mixture during the cold start phase, there is an increased amount of uncombusted 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
- After cold start, the ECM -2-starts the secondary air pump -12-via the relay for Secondary Air Injection (AIR) -1-. Air is blown to the mechanical secondary air valve -10-.
- Parallel to this, the Secondary Air Injection (AIR) solenoid valve -3- is activated, which permits negative pressure to reach the mechanical secondary air valve -10- and the pressure unit for charge air pressure regulation -7-.
- The mechanical secondary air valve thereby opens the path for secondary air to the exhaust channels of the cylinder head.
- To prevent unnecessary heating, secondary air is led around the turbocharger. For this, the charge air pressure regulation pressure unit opens the charge air pressure valve. The pressure unit, designed as a double reservoir, has a vacuum connection for this on the intake 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 side): Arrow points in direction of flow as shown in diagram
6 - Vacuum reservoir
- Mounted at cylinder head cover
7 - Pressure can for charge air 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-