Air injection - function - GF14.30-P-3012SM

ENGINE 113.986 

ENGINE 113.987 

ENGINE 113.988 

ENGINE 113.989 

Fig 1: Air Injection Function Diagram - Engine 113.988

The air injection more rapidly warms up the catalytic converters to operating temperature after starting and thus improves the exhaust emission values in the warming-up phase.

The injected air is prepared by the electric air pump (M33) with released air injection. The electric air pump is actuated by the ME-SFI [ME] control unit (N3/10) via the air pump relay (K40/7kN, N10/1kO).

The air pump switchover valve (Y32) is also actuated by the ME control unit at the ground end at the same time.

Air injection is actuated for maximum 150 seconds after engine start, if:

• Coolant temperature at start > -10°C < 35°C
• Engine speed < 3000 rpm
• Throttle valve is not fully open (no full-load range)

The air pump switchover valve switches the intake manifold vacuum (a) through to the aspirator shutoff valves (126/1, 126/2). These open and the injected air (b) is injected into the cylinder head (outlet duct) (c).

The injected air reacts with the hot exhaust gases in the outlet port. An oxidation of carbon monoxide (CO) and hydrocarbon (HC) takes place (afterburning).

This leads to an additional increase of exhaust gas temperature (exothermic reaction), which warms up the catalytic converters more rapidly.