Dr. Ing. h.c.F. Porsche AG has released detailed technical information on its upcoming Cayenne sport utility vehicle (SUV), including information describing the Cayenne’s permanent four-wheel drive system.
With the Cayenne — Porsche’s third model line — the company will introduce its Porsche Traction Management (PTM) permanent four-wheel drive system, a pneumatic suspension system with a self-leveling feature and six adjustable ride height positions, and Porsche Active Suspension Management (PASM), which is an electronically variable damping system that stabilizes body sway during sudden gas or brake pedal applications or when driving on rough terrain. These systems work together to ensure the Cayenne offers an optimum blend of supreme on-pavement and equally outstanding off-pavement driving qualities.
Porsche Traction Management – the new generation of four-wheel drive One highlight is the Porsche Traction Management (PTM) permanent four- wheel drive system, which is standard on both Cayenne models and feeds 62 percent of the engine power to the rear wheels and 38 percent to the front wheels in the basic mode. A multiple-plate clutch operated by an electric motor and controlled electronically is able to vary the distribution of power according to specific driving conditions, whenever necessary feeding up to 100 percent of the engine torque either to the front or the rear. The map-controlled longitudinal differential lock and the rear axle differential, available as an option, not only respond to any lack of traction on the front or rear wheels, but also incorporate sensors measuring vehicle speed, lateral acceleration, the steering angle, and gas pedal operation. PTM calculates the optimum locking action on both axles and spreads out drive forces as needed to the front and rear wheels. Therefore, PTM might be compared with a forward-looking, anticipative active electronic control system providing exactly the right balance for superior driving stability and supreme safety when changing lanes both at high speeds or when driving at a moderate pace on ice and snow. Some of the particular benefits PTM provides are:
* excellent driving stability and traction in all situations, regardless of surface friction,
* better steering and control by opening the longitudinal differential lock in order to avoid any understeer,
* enhanced vehicle control when driving to the limit, due to the longitudinal differential lock,
* improved directional stability and tracking control by appropriate activation of the longitudinal differential lock, and improved traction by increasing the degree of locking action before the wheels start to spin.
Porsche Stability Management (PSM), also standard on Cayenne, maintains a constant dialogue with PTM but only intervenes when the vehicle reaches its physical limit. Coordinating essential systems such as the anti-lock brake system (ABS), the automatic slip regulation (ASR), and the automatic brake differential (ABD), PSM is immediately available whenever the Cayenne enters critical over- or understeer conditions, “telling” PTM to open the differential locks in order to re-stabilize the car by applying the brakes specifically on individual wheels. Sporting and agile on the road; robust when driving off the beaten track The suspension provides the secure foundation for supreme driving dynamics combining optimum safety, motoring comfort and off-pavement driving capabilities. The front axle, which is newly developed for the Porsche Cayenne, is an extra-large double track control arm configuration mounted on its own subframe.
The large distance between the individual track control arms keeps forces acting on the suspension to a minimum, thus ensuring precise wheel guidance for supreme agility and an extremely low level of any adverse forces. Incorporating extra-large rubber mounts, the elastic subframe bearings additionally serve to keep out any road noise with maximum efficiency. Made of high-strength steel, the subframe design has an arch-shaped crossbar and inclined ramps at the front that give the Cayenne ample ground clearance of up to 273 mm, or 10.75 inches. The steering transmission with its variable transmission ratio and the differential are both well protected on top of the subframe to help guarantee robust off-pavement driving qualities. The rear axle is another new Porsche development. The rear axle configuration is an elaborate multi-arm concept easily able to handle both high traction forces and the Cayenne’s high service load capabilities. In the interest of extra comfort and noise reduction, the rear axle is also mounted on a subframe resting on extra-large, hydraulically dampened rubber bearings.
Again, the subframe is made of high-strength steel for optimal weight and maximum structure stiffness. The lower track control arm and the tie-rod are both made of steel plate to ensure robust strength even on the roughest surfaces. The upper track control arm assembly, which is well protected within the vehicle, is made of extra-light forged aluminum components. Through its particular configuration, the axle kinematics reduces undesired squat and dive when accelerating and braking, keeping the Cayenne almost entirely level on the road at all times. The rear axle configuration and the rear toe-in control stabilize the vehicle’s driving behavior particularly in bends and under load change. A special feature of the axle concept is the extra-long spring travel for off-pavement purposes.
The pneumatic spring suspension, standard on the Cayenne Turbo, comes with inward and outward spring travel of 102 and 118 mm (4.02 and 4.65 inches), respectively, on the front axle, and 124 and 125 mm (4.88 and 4.92 inches) at the rear. Inward and outward spring travel on the steel spring suspension of the Cayenne S is 104 and 116 mm (4.09 and 4.57 inches), respectively, at the front and 135 and 98 mm (5.31 and 3.86 inches) at the rear.
As an option, the Cayenne S is also available with pneumatic, air-controlled spring suspension. Pneumatic suspension with self-leveling and adjustable ride height Pneumatic suspension not only guarantees extra ground clearance on rough terrain, its self-leveling feature provides a consistent vehicle position regardless of the load.
The system also ensures maximum driving pleasure and active safety by automatically lowering the Cayenne relative to increasing road speed. Incorporating six different ride height levels, the pneumatic suspension adjusts over a range of 116 mm (4.57 inches).
In normal trim, ground clearance is 217 mm (8.54 inches) according to the DIN unladen standard.
In load trim, the Cayenne moves down 60 mm or 2.26 inches from its standard position to a loading level of 157 mm or 6.18 inches. This level is only available when the vehicle is not moving and allows extra ease for loading and unloading. When the setting is off, the system automatically returns to its normal level.
In low trim, the Cayenne moves down 27 mm or 1.06 inches below its standard trim and is comparable to a vehicle with a fully-fledged sports suspension. In practice this means the suspension is firmer and air resistance is lower, making the Cayenne even more stable and dynamic at high speeds. The suspension level lowers from a higher position to the low high-speed setting at a road speed of 125 km/h or 78 mph.
At speeds exceeding 210 km/h or 130 mph, the Cayenne automatically moves down to its extra-low ride level, which is 11 mm or 0.43 inches below the “regular” low setting.
When driving off-pavement, the Cayenne can be set to the higher off- pavement level up to 26 mm or 1.02 inches over the standard ride height to negotiate difficult terrain. However, this high level is only available at speeds up to 80 km/h or 50 mph.
The special off-pavement level is for the most extreme driving conditions, raising the Cayenne another 30 mm or 1.18 inches to a ground clearance of 273 mm or 10.75 inches. This extra-high level is only available at speeds of up to 30 km/h or 19 mph. Active damper control Porsche offers pneumatic
suspension in combination with Porsche Active Suspension Management (PASM), a new variable damping system. Operated electronically, PASM adjusts damper forces infinitely as a function of surface conditions and the driver’s driving style. A typical example of PASM intervention is during powerful application of the gas and/or brake pedal or when driving on particularly rough terrain. PASM serves to steady any body sway and dive motions by monitoring body movement through five accelerometers. As soon as the motion of the Cayenne’s body exceeds a certain limit depending on specific driving conditions, PASM intervenes and stabilizes the vehicle by acting on the individual dampers.
PASM also gives the Cayenne driver the opportunity to choose among three damper settings while driving — Comfort, Normal or Sports. Consistently operating in the background, PASM always maintains its active control function, comparing the operator’s driving style with the program currently in use. Whenever the driver has chosen a particularly comfortable damper setting but is driving in a more sporting or dynamic style, the system automatically switches over to the sports mode and makes the dampers firmer. A real champion on rough terrain The Cayenne’s outstanding road performance does not come at the expense of its off-pavement capabilities. Due to its intelligent four-wheel drive, the Cayenne is able to handle minor off-pavement conditions without requiring modification of the traction systems.
When driven on rough terrain, the Cayenne uses the Porsche Traction System integrated as a standard feature in the power divider. This reduction gearbox comes with a 2.7:1 gear ratio for even the most extreme off-pavement driving maneuvers. By activating the low range mode by way of a toggle switch on the Cayenne’s center console, several control systems are automatically prepared for off-pavement conditions. PTM switches to the appropriate gear ratio for off-pavement driving and activates a special off-pavement control map for the differential locks. PSM switches on the traction-oriented off-pavement ABS and ABD system, and the pneumatic suspension in the Cayenne Turbo automatically changes to the off-pavement ride level.
Porsche is the first car manufacturer to offer this combination of systems controlled by a central off-pavement switch, thus reducing the risk of control errors when driving on rough terrain. The Cayenne’s standard off-pavement driving characteristics can be enhanced to a higher level. In the event individual wheels lose contact in demanding terrain, a direct and rigid connection of the four-wheel drive system provides mobility.
Operating the off-pavement switch a second time activates the 100 percent front-to-rear differential lock, and the Cayenne Turbo’s standard pneumatic suspension provides additional assistance when climbing. In the special off-pavement mode, which provides 273 mm or 10.75 inches ride height, the inclination angle is up to 32 degrees at the front and 27 degrees at the rear, enabling the Cayenne to handle steep ramps. Even extreme crests when driving from one gradient to another are not obstacles since the 25-degree ramp angle prevents the body between the axles from touching the ground prematurely.
Both models are equipped for water crossing up to a half meter deep (556 mm or 22 inches when set to the special off- pavement level) thanks to the Cayenne’s special sealing concept, a high-rise intake funnel, its elevated transmission purge opening, and full encapsulation of the side sills. Save traction even on the roughest terrain As an option, Porsche offers the Advanced Offroad Technology Package for the most extreme off-pavement conditions. Apart from special side protection and a steel plate underfloor panel around the radiator, this package includes a fully controllable (up to 100 percent) differential lock on the rear axle. To fully activate the lock, the driver operates the central off-pavement switch a third time. The fully controlled rear axle lock then ensures even better traction when setting off on slippery surfaces with varying frictional coefficients and in bends. The package also uses anti-roll bars on the front and rear axle, which are hydraulically activated and deactivated by a switch in the center console.
This increases front and rear axle lock by 70 mm or 2.76 inches, which improves ride comfort by minimizing body sway and enhancing off-pavement driving qualities and traction when negotiating rocks, tree trunks or bumps. To ensure the Cayenne’s sporting driving qualities on the road, the anti- roll bars can only be disconnected in the low range mode.
As soon as the Cayenne, with its anti-roll bars disconnected, returns from rough terrain to the road, the anti-roll bars are automatically reconnected once the vehicle exceeds 50 km/h or 31 mph to provide the additional stability required for on- pavement driving as a safety feature. Featuring an all-new, Porsche designed and manufactured 340 bhp (DIN) V8 engine, the Cayenne S accelerates from 0 to 100 km/h (0 to 62 mph) in 7.2 seconds and reaches a top speed of 242 km/h or 150 mph.
The Cayenne Turbo also features a 4.5-liter V8 engine, but develops a maximum of 450 bhp (DIN) thanks to two exhaust gas turbochargers complete with intercoolers. This ensures acceleration from 0 to 100 km/h (0 to 62 mph) in 5.6 seconds with a top speed of 266 km/h or 165 mph. Cayenne production will take place in Leipzig, Germany, in a newly constructed manufacturing facility, but its engine – or heart – will be built in Zuffenhausen.
Porsche will produce approximately 25,000 Cayenne SUVs during the first full year of production, 70 percent of which will be for export worldwide, including the United States and Canada.