Front Axle With Air Suspension

Front Axle With Air Suspension

- Double-wishbone front axle with subframe
- Lower wheel carrier and upper wishbone made of aluminum
- Integrated spring/damper unit screwed directly onto body (omission of mounting saddle)
- Supporting mount with optimized damping characteristics on the front axle (Cellasto inserts)
- Hydraulic mount on the lower rear wishbones
- Steering gear with variable steering ratio and regulated power-steering pump (Servotronic option)
- Tube-type anti-roll bar
- PDCC optional







NOTE: Markings are provided on the housing to permit identification of the central steering position.

Wheel bearing housing

The wheel bearing housing (1) is made of aluminum and accommodates the screw-in angular-contact ball bearing (3) and the speed sensor (2). The wheel flange (4) is still pressed into the wheel bearing.







Steering







Like all Porsche models, the Cayenne models are equipped as standard with a rack-and- pinion steering gear with hydraulic assistance and variable steering ratio. The steering ratio is still variable, but has been designed to be even sportier, i.e. the ratio (i) in the center position is 15.9:1 and becomes more direct as the steering angle increases (up to i = 12.5:1). It is now more direct around the center position in particular. The turning circle is approx. 39.04 ft. (11.9 m).

Regulated steering hydraulics

The Cayenne models are equipped with a regulated power-steering pump with variable geometric delivery rate. The demand-controlled delivery rate reduces energy consumption and thus lowers fuel consumption.

Function







The pump delivers a constant volume flow to the hydraulic power steering when the engine is idling. When the engine speed increases, this causes the internally rising pump pressure to open the control valve (11), apply pressure on the cam ring (5) and reduce eccentricity with respect to the rotor (3). As a result, the pump chambers become smaller and only produce a reduced delivery rate. This restricted pump function prevents overproduction of pressure oil and significantly less energy is required at higher pump speeds due to reduced power consumption. This makes it possible to simplify cooling measures in the steering system. As the engine speed decreases, the pressure differential that exists between the left and right chambers increases the eccentricity between the rotor (3) and the cam ring (5). As a result, the geometric delivery rate increases continuously again.

Servotronic







Servotronic, a speed-sensitive power steering system, is optionally available for all Cayenne models. The steering is firm at high speeds and steering maneuvers are extremely precise with excellent steering comfort. At low speeds, on the other hand, Servotronic permits easy maneuvering and parking.

Structure

The front-end electronics control unit (VWE) receives information about the vehicle speed and vehicle variant via the gateway. The Servotronic valve is controlled by a corresponding PWM signal from the front-end electronics.







Safety

The steering remains fully functional in the event of a malfunction. If the power supply fails, the converter valve opens to its maximum position, i.e. maximum hydraulic feedback or "high-speed characteristic".