We attended a technology workshop in Germany to find out how Porsche’s new Cayenne merges SUV capability with sportscar performance…
The test track is wet, but the Porsche driver is pushing on with confidence, working his way through comfort, sport and sport+ modes to illustrate the differences. The 4,0-litre V8, delivering 404 kW in the Cayenne Turbo, responds beautifully to the commands of the pilot. Then he turns off traction control and throws the Cayenne, to my delight, into a mighty power slide. Is this the same SUV that scaled the inclines on the off-road course minutes before? Surely such sportscar-like hooliganism should not be possible in an SUV? Porsche thinks otherwise, and during the workshop it had all the Cayenne’s go-faster technology on display.
Body
Mass is crucial when it comes to dynamic performance and this also applies to an SUV. The Cayenne now uses more aluminium than ever before (47%) in its body construction, including the entire outer skin, and that shaves 135 kg from the bodyshell compared with the second-generation Cayenne. According to Porsche, this is the highest-percentage aluminium content currently possible that still meets stringent crash-safety requirements.
High-strength steel is employed to provide adequate rigidity to the crash structure. Although composite materials will be used more extensively in future to further trim mass, the technology is currently too expensive for a mainstream application such as the Cayenne. Interestingly, the exterior paintwork adds 20 kg to the vehicle’s overall mass.
Chassis
Porsche employs the VW Group’s MLB platform that’s shared with the Audi Q7, but tuned for the Cayenne, most notably the front and rear axles, where 48 V electro-mechanical roll bars are found. The electric motors in the roll bars can supply up to 1 200 N.m in milliseconds to reduce body lean during enthusiastic cornering. The system can also decouple the wheels during off-road driving, where maximum wheel articulation is needed to enhance grip.
The front suspension has changed from a double-wishbone setup to multilink, allowing for better control of the wheels across the Cayenne’s wide application framework.
The air suspension now utilises three-chamber air springs on each strut. This permits a wider range of spring rates than before and enhances both the vehicle’s dynamic ability and comfort levels. As the high centre of gravity of an SUV affects handling prowess, the new air-suspension system offers five ride height options stretching from 162 to 245 mm of ground clearance. The lowest setting is enabled by the chassis control system at speeds over 210 km/h.
Rear-wheel steering, shared with the 911 and Panamera, makes its debut on the Cayenne. The rear wheels have limited steering movement owing to the flex in the suspension rubbers rather than a rotational degree of freedom (as with front wheels). The turning of the front and rear wheels in opposite directions below 80 km/h adds agility and shrinks the 12,1-metre turning circle by 0,6 metres (mimicking a shortened wheelbase). At higher speeds, all the wheels turn in the same direction to increase stability.
For the first time, Porsche has fitted wider tyres at the rear (on the Turbo, 315/35 ZR21 aft versus 285/40 ZR21). This, in combination with the rear-biased torque split, allowed the engineers to improve the dynamic ability further.
Kerb the problem
Those large wheels may be good for dynamics and putting power to the road, but they’re prone to kerbing. Porsche has developed an innovative solution where the surround-view camera system detects the kerb and warns the driver to avoid impact (and brakes once). The driver can override the system with a press of
the accelerator.
Powertrains
To provide sportscar-like acceleration, high power outputs are needed to increase the power-to-mass ratio. The Cayenne range will be launched with three turbopetrol engines: a 250 kW/450 N.m 3,0-litre with a single turbo; a 2,9-litre twin-turbo with 324 kW/550 N.m; and the range-topping 4,0-litre V8 with
404 kW/770 N.m (that results in a 0-100 km/h time of 4,1 seconds).
Interestingly, the 2,9-litre engine features a hot-V turbo layout to increase response. It utilises the same block as the 3,0-litre, but because of the high boost values required, the stroke is shortened to lower the compression ratio and prevent knock (auto ignition). This engine is also found in the new Audi RS4/5.
Porsche will use a conventional, eight-speed torque-converter transmission from ZF, as it fits the demands of an SUV better in terms of off-roading and towing ability.
Although the power is delivered to all four wheels to increase traction, the Cayenne is predominantly rear-biased until slip is detected before a clutch on the front differential sends torque to that axle. This setup results in dynamic behaviour more akin to a performance car than an SUV.
3,0-litre single turbo: 250 kW/450 N.m
2,9-litre twin-turbo: 324 kW/550 N.m
4,0-litre V8: 404 kW/770 N.m
Brakes
A world-first for any vehicle is Porsche’s surface-coated brakes. They’re essentially steel brakes with a tungsten-carbide coating. Making them involves a laser adding the coating to the steel discs. In combination with special brake pads, this system offers increased stopping power but also 30% less wear (and brake dust) than before. This breakthrough fills the cost and performance gaps between normal steel discs and the ultra-expensive, carbon-ceramic option. The discs are gripped by 10-piston callipers up front and four-piston ones at the rear.
Aerodynamics
Another first for an SUV is an adaptive rear spoiler that can function as an air brake, too. At speeds above 160 km/h, the spoiler tilts by six degrees to aid stability by increasing the downward force on the rear axle. In sport+ mode the spoiler tilts to 12,6 degrees for enhanced road holding in faster bends. The angle is further increased to almost 20 degrees when the panoramic sunroof is open to help balance the air turbulence over the roof. The maximum 28,2-degree tilt is reserved for the air brake function that operates when braking between 170 and 270 km/h. According to Porsche, the spoiler can reduce the braking distance from 250-0 km/h by nearly two metres.
Further aerodynamic enhancements include active cooling shutters behind the front bumper. This technology solves the conflict between necessary cooling performance and optimised aerodynamics. The cooling shutters open only when additional cooling is needed. The underbody is almost completely covered to improve airflow under the vehicle and further optimise aerodynamic performance.
Adaptive roof spoiler
Porsche says the rear spoiler can reduce the braking distance from 250-0 km/h by two metres…
Author: Nicol Louw
