Suspension: Description and Operation
Special Functions of Level Control
Loading or Unloading
If vehicle height with respect to the road changes as the result of loading or unloading. the control module readjusts the vehicle to the specified level (only with the tailgate open).
Air is supplied over the solenoids to the appropriate air spring or vented through the bleed valve.
Switching Off Level Control
In particular situations it may he necessary to switch off level control, or example when changing a wheel or during operations on a hoist.
Level control is switched off by pressing the toggle switch forward for approximately 5 to 1O seconds.
The multi-function display indicates that level control has been switched off.
Activating Level Control
Level control is activated again by pressing the toggle switch forward for approximately 5 to 10 seconds or automatically by the control module recognizing a drive situation.
Hoist without Previous Deactivation (Ignition OFF)
It the vehicle is raised on a hoist without previously switching oft level control, air is bled out of all four air springs until the control module recognizes this situation (hoist recognition). Hoist recognition is when a specific change in height was detected during a specific time.
As a result, when the hoist is lowered, the vehicle can be sitting lower than before. With the ignition ON, or when driving, the vehicle is raised again to the Normal level automatically.
Recognizing a Snow Bank (only with engine running)
If the vehicle is driven onto a snowbank, for example (wheels are turning freely), the system recognizes a rapid change in height of the entire vehicle. Since the engine is running in this situation, the conditions for "hoist recognition" do not exist. So no air is released from the springs.
Action of Pneumatic Suspension Following "Ignition OFF"
Loading and Unloading Procedures
Following "Ignition OFF", the control module remains active for one or two minutes and, with sufficient pressure in the pressure reservoir, can still complete level control procedures initiated, for example, by loading and unloading.
Gradual Changes in Level
To compensate for gradual changes in level which can be caused by heating of the air while driving and subsequent re-cooling after the trip is completed, the system is readjusted after approximately 15 minutes and after 2 hours to reach the optimal ride height.
Tire Inflation (Ignition ON)
The compressed air connection is located at the left front of the right front seat. The tire inflation hose is under the left rear seat cushion. When the inflation hose is connected, a reed contact is signaled. The pressure reservoir is opened, so that a pressure of 8 bar is available. As soon a drop in system pressure is detected, the compressor is powered up.
To prevent the fill hose from being damaged, a maximum pressure of 8 bar is permitted (dynamic pressure monitoring). A static pressure test takes place every 15 seconds. The air supply is shut oft at a pressure of approximately 4 bar to prevent the space-saver spare wheel from being destroyed.
To protect the compressor, it is switched off after running for 10 minutes or at a compressor temperature of approximately 100 degrees C. The compressor cannot be re-started until after a waiting period and cycling the ignition off/on.
Vehicle Transportation
When transporting the vehicle on a transporter, on car4rains and ferries, it must be tied down only at the wheels.
Damping Force Control
Standard equipment on the Cayenne Turbo includes the pneumatic suspension system, and the shock absorber system with damping force control continuously adjusted to the situation. The pneumatic suspension system with damping force control is optionally available on the Cayenne S.
Three damping programs are available. Comfort, Normal and Sport, which can be selected individually by a toggle switch.
The control system for damping force control reads the condition of the road or the motion of the vehicle through two wheel and three body accelerometers.
The characteristic curves for the individual shock absorbers are shifted in accordance with the calculated damping requirements
Continuous damping control is based on shock absorbers whose curves can be adjusted electrically.
Damping force is adjustable as a function of a map through the proportioning valve located at the shock absorber.
In this way it is possible to adapt damping force to the driving situation and road condition within milliseconds.
The system attempts to adjust damping force using the skyhook control strategy" (body level).