The Audi S4: Electronic Damper Control
Audi drive select with the sport differential can be combined with electronic damping control. The gas-filled hydraulic shock absorbers have an additional valve with a continuous opening action. The control unit computes the optimal damping force at a cycle frequency of 1,000 per second.
The electromagnetically controlled valve selects a damping characteristic to match the current driving situation at any given moment. Higher damping force may be needed to resist body movement when cornering rapidly or braking, whereas a lower damping force will be appropriate on potholed roads and a moderate setting on poor country roads.
14 sensors, 1,000 calculations per second
The central element in electronic damper control is the new high-performance control unit. It has the imposing data spread of 32 bits and operates at high speed. The computer analyses the signals from 14 sensors continuously, and calculates the current for the electrically controlled shock absorbers at each individual wheel a thousand times a second.
The so-called CDC shock absorbers (CDC = continuous damping control) are gas-filled hydraulic units based on the twin-tube principle, featuring an additional external valve and a connecting pipe.
An electromagnetically energized proportional-action valve opens against the force exerted by a spring and regulates the flow of hydraulic fluid between the inner and outer shock-absorber tubes. A smaller flow cross-section makes the damping characteristic firmer, a larger one makes it softer.
The control unit applies adaptive operating characteristics within the mode the driver has chosen via Audi drive select. Even from the comfort mode, the shock absorbers switch to a firmer setting at lightning speed if required. The control unit sets the optimum damping power for every driving style and for every type of road.
The equipment, data, and prices specified refer to the models offered in Germany. Subject to amendment; errors and omissions excepted.