Porsche’s pioneering Cayenne crossover SUV enters its third generation in 2018 following six-year runs of both the first- and second-generation models. In its latest iteration, new technology permits the Cayenne to get ever closer to reconciling the conflicting priorities of its Porsche sports-car heritage and its SUV off-road expectations.
The 2018 Cayenne is helped in its progress toward this by a lighter-yet-stronger unibody structure made with both aluminum and various grades of steel; it is Porsche’s interpretation of the Volkswagen Group’s MLB Evo platform, which debuted in 100 mm-longer form as the Audi Q7.
The MLB Evo architecture replaces the previous Cayenne’s rubber bushing-mounted steel front subframe with a new bearing-mounted aluminum subframe that is lighter and contributes to improved steering response.
Much of the body-in-white is aluminum, including the roof, floorpan, front section, doors, fenders, hood and hatch. This is strategically reinforced by micro-alloyed high-strength steel and multi-phase steel to produce a body that is 20% more rigid than that of the outgoing model while trimming 298 lb (135 kg) from the bodyshell.
Some of the hard-won weight savings was lost due to the increase in standard equipment that reduced the final curb-weight reduction, reported a dismayed-sounding Karl Heess (pronounced “Hayes”), chassis director for the SUV product line.
The 2,020-kg curb weight of the Cayenne S, for example, is 143 lb (65 kg) less that the previous model. Because of differences in standard equipment, the 4,376-lb. (1,985-kg) base Cayenne saves 121 lb (55 kg), while there is a paltry 22 lb (10 kg) reduction for the 4,795-lb (2,175-kg) Cayenne Turbo. Ten kg of every model’s savings is attributable to the substitution of a lightweight lithium-ion battery in place of the lead-acid battery used previously.
Much of the Turbo’s extra weight can be attributed to its gargantuan brakes. They are 16.34-in (415-mm) cast-iron front rotors squeezed by suitably enormous Akebono 10-piston monobloc aluminum front calipers and 14.37-in (365-mm) cast-iron rear rotors with Brembo four-piston monobloc aluminum calipers. The oversized brakes are a necessity for such a heavy vehicle propelled by a 550-hp, twin-turbocharged 4.0-L V8 engine capable of producing 3.9-sec 0-60 mph (0-97 km/h) acceleration and a top speed of 178 mph (286 kph)
The base Cayenne uses 13.8-in (350-mm) front brakes with four-piston monobloc aluminum calipers and 13-in (330-mm) rear rotors with two-piston aluminum monobloc calipers, while the Cayenne S employs larger 15.35-in (390-mm) front rotors with six-piston aluminum monobloc calipers and 13-in rear rotors with four-piston aluminum monobloc calipers. All of these components are Brembo-supplied.
All of the Cayenne’s cast-iron rotors have a tungsten-carbide coating, which both boosts rotor life by 30 percent and reduces the amount of wheel-dirtying brake dust produced.
Twenty-one-inch wheels are standard on the Turbo to provide necessary space for the huge brakes, while 19-inch wheels are standard on the base and S models, with 21-inch wheels available optionally.
The base engine is a 340-hp single-turbo 3.0-L V6, while the S enjoys 440 hp from a 2.9-L twin-turbo V6. Both engines are from the same family, but the larger one has a 3-mm-longer stroke. A plug-in hybrid-electric and a diesel will follow, but the company declined to provide details on those versions.
All three gasoline-powered models use an 8-speed ZF Tiptronic S planetary automatic transmission with an added “hang-on” power take-off to drive the front wheels. This is a difference between the rear-drive-biased Cayenne—which can send 100% of its power to the rear wheels—and the Audi Q7’s quattro full-time all-wheel drive system that's always dividing drive torque between front and rear axles.
Vibracoustic damping, rear-steer
Heess pronounced the biggest technical challenge for the chassis team to be the development of the new three-chamber Vibracoustic air suspension system that lets the Cayenne so effective marry its conflicting goals of comfort and agility. The air suspension is standard equipment for the Turbo, while conventional steel springs are standard on all other models, with the air suspension available optionally.
The new three-chamber system provides a greater range of damping rates, which is especially beneficial in hard driving because the smallest-volume chamber now provides very high rates, according to Heess.
Ground clearance varies between 6.37 in. (162 mm) and 9.64 in. (245 mm), depending on whether the driver has selected the Normal, Sport or Sport+ driving mode. The Cayenne automatically drops to its lowest height when driving faster than 130 mph (210 km/h) for reduced drag and improved stability; it can crouch even lower when parked for easier loading of luggage.
The Cayenne’s balance of sport and comfort also benefits from a new Schaeffler Group-supplied 48-volt Intelligent Active Roll Control roll-stabilization system, which can completely disconnect the anti-roll bar, as when driving off road and maximum suspension articulation is desirable and to apply as much as 885 lb·ft (1200 N·m) of resistance to roll during hard cornering. The previous Cayenne used a hydraulically-powered active roll bar, which was replaced because the electric system is more compact, responds faster and uses less energy.
A new feature for the 2018 Cayenne is a rear-wheel steering system that can turn the wheels as much as 3 deg in either direction. At speeds below 50 mph (80 km/h), the rear wheels turn in the opposite direction to the fronts, providing improved agility and reduced turning radius for parking. The turning circle is reduced from 39.7 ft (12.1 m) to 37.7 ft (11.5 m).
Above 50 mph (80 km/h), the rear wheels steer in the same direction as the fronts, for improved stability, especially during lane-change maneuvers.
The new Cayenne is the first Porsche model to bring all these disparate chassis-control solutions under the common command of an integrated system dubbed called Porsche 4D Chassis Control. Previously, each subsystem had its own sensors and control module, but the new 4D system coordinates all the subsystems centrally, providing control that Porsche considers to manage the fourth dimension, time, by acting proactively to anticipated events.
We can anticipate that the base Cayenne and the S will arrive in the U.S.mid-2018, with the Turbo available later in the year.Continue reading »