Damping valve, function - GF32.31-P-4300-02B

Illustration shows front axle suspension strut 

The reed valves (a, b, c, d) consist of a ball valve and throttle. 

The ADS suspension control module is used to achieve four different damping force settings.

Damping force setting 1 

For comfortable rolling with small sprung mass vibrations and low longitudinal and lateral acceleration. With this damping force setting both solenoid valves y1 and y2 are open so that most of the oil flows parallel to the hard rebound and compression of the operating piston via the softer reed valves at the solenoid valves. The comfort rebound and compression setting is therefore achieved.

Damping force setting 2 

The reed valves at the valve piston generate a firmer setting. If the vehicle is lowered, solenoid valve y2 is opened and solenoid valve y1 is closed. The reed valves (a = hard compression and b = soft rebound) at solenoid valve y1 generate a hard compression and a soft rebound.

Damping force setting 3 

The reed valves at the valve piston generate an even firmer setting. If the vehicle is raised, solenoid valve y1 is opened and solenoid valve y2 is closed. The reed valves (c = hard rebound and b = soft compression) at solenoid valve y2 generate a hard rebound and a soft compression.

Damping force setting 4 (driving safety setting) 

For increased driving safety with high longitudinal and lateral vehicle acceleration. Both solenoid valves y1 and y2 are closed. The reed valves (a = hard compression and c = hard rebound) generate a hard compression and rebound. All the oil flows via the hard rebound and compression of the operating piston.

This damping force setting is also selected if the ADS system fails and the ADS suspension warning light (A1e27) comes on in the instrument cluster.

Damping force setting	Damping valves (Y51-Y54)		Valve control
	Rebound	Compression	Solenoid valve (y1)	Solenoid valve (y2)
1	Comfort	Comfort	Open	Open
2	Soft	Hard	Closed	Open
3	Hard	Soft	Open	Closed
4	Hard	Hard	Closed	Closed