Porsche pioneers DCT in the luxury segment
One of the penalties of having a technical reputation as sky-high as that of Porsche is that expectations invariably run absurdly high in advance of a new model introduction. And when that introduction is in a sector new to Porsche – such as the premium SUV segment with the Cayenne in 2002 or the luxury sedan market with the Panamera this autumn – there is the implicit assumption that the new Porsche will be comfortably superior to the current champion players in the field, again ratcheting up the stakes.
The new and much-awaited Panamera is designed to steal sales away from large luxury staple products such as the Mercedes-Benz S Class and BMW 7 series, as well as from more diverse premium offerings such as the Range Rover and Bentley Continental GT. Inevitably, however, the Panamera will be most closely compared with the big Mercedes and BMW, yet its sporty, low-slung format allows it to avoid a full head-on confrontation; instead, Porsche sees it as opening up a new segment for ‘gran turismo’ sedans combining good - rather than opulent - comfort for four, reasonable luggage space and powerful, continent-crossing performance capable of providing a genuine sports-car driving experience.
Porsche will not be alone for long in this new, racier class of super-sports sedans: the niche is set to expand as other big names such as Aston Martin field four-door luxury models with the sleek coupé profile of a sports car.
There is no mistaking the fact that the Panamera is a Porsche: the dimensions may be swollen and the doors may number four rather than two, but 911 is clearly written on every surface and in every detail. The stance is low and sleek: the driver sits as low as in a 911, and the messages are those of an agile sports car rather than an overweight limousine. In its engineering, too, the Panamera favors sports-car solutions over the familiar luxury choices: most notably, Porsche has rejected a conventional planetary automatic transmission and opted for a seven-speed dual clutch transmission, supplied by ZF – which already provides DCTs for the 911, Cayman and Boxster.
This is the first time a DCT has been fitted to a high-end luxury vehicle. In practice the PDK – Porsche's label for the DCT -- will be the default choice for customers: it is standard on the Turbo model, with its four wheel drive and 500hp engine, as well as on the non-turbo 4S, with 400hp; only the entry-level S model, with rear wheel drive, is available with a six-speed manual - again a rare choice in the luxury market.
With a vehicle mass of almost two tonnes and the 4.8 liter turbo V8 engine delivering 770Nm of torque on overboost, the DCT application is one of the most demanding so far developed; its task is made tougher still by the fact that in parallel with handling so much power and torque the transmission must attain the extreme levels of refinement set by ZF’s own six- and eight-speed planetary automatics in the luxury segment.
Further complication is added by the transmission's built-in stop-start system, again a first for the luxury sector. While the PDK gearbox uses the same basic principles as that on the rear-engined 911 sports car, it differs in that a single oil circulation circuit is employed to cover the clutches, gears and hydraulic system; the 911 uses two separate circuits.
Porsche has taken full advantage of the move to DCT to provide an exceptionally wide spread of gear ratios. First gear is set deliberately low, making the shift to second gear imperceptible and almost instantaneous when moving off from rest, while the very tall seventh gear provides quiet and economical cruising. Porsche claims that this broad ratio spread of 10.1 - much the broadest in the industry - helps the PDK transmission reduce the Panamera's fuel consumption by 0.8 liters per 100km; the stop-start system saves a further 0.6 liters and reduced internal friction in the driveline accounts for a saving of 0.4 liters. The clutches have diameters of 164 and 220 mm and the final drive ratio is 3.15.
The driver interface to control this complex transmission is simple: a central shift lever with a conventional PRND pattern, plus a left gate allowing manual shifts; on the steering wheel spokes are two-way buttons for up- and downshifts. There are no separate controls to adjust the mode of the transmission: instead, the system's parameters are altered along with the throttle mapping, stability control, suspension and ride height settings and other factors when the driver presses the Sport button. On models equipped with the optional Sport Chrono package, a Sport Plus setting with more extreme values can be selected.
Keen responses
The low, snug seating position, deep transmission tunnel and small, vertical steering wheel provide the Panamera driver with all the right messages: so too does the sharp snarl of the engine as it starts, though it straightaway settles down to a distant rumbling idle. Putting the lever into D to move off, the transmission feels just like a planetary auto in its smoothness: in the car's comfort mode, the initial throttle response is smooth and gentle and the box quickly shifts up into its higher ratios.
The very tall seventh gear allows the engine to relax and save fuel at speed: at 200km/h (124mph) it is turning over at only 2800rev/min: maximum speed is attained in sixth.
The transmission becomes more responsive as the driver pushes harder, even blipping the throttle when braking and downshifting for a bend. But it takes a prod of the Sport button - hard to find intuitively without taking one’s eyes off the road for a moment – to ensure the transmission downshifts unprompted into bends and that the throttle blips for driver-provoked downshifts. Engaging Sport Plus heightens these responses, the Panamera holding on to its lower gears much longer, especially in bends, and shifting down earlier, too.
Even on the racetrack the PDK-equipped Panamera proves a rewarding experience: the gear changes snap through quickly, but still seamlessly under maximum power: there’s no mechanical jolt as there can be on some track-oriented systems. With the Sport Chrono package fitted, the Panamera Turbo has an impressive party trick up its sleeve: full-bore race starts under the Launch Control strategy. Holding the brake with the left foot, the driver applies full throttle, quickly: the system recognizes the Launch Control condition and stabilizes the engine revs at 4800. Releasing the brake unleashes a mighty surge of sustained acceleration right the way to 160km/h and beyond, with remarkably smooth shifts considering the amount of power being handled. Porsche confirms that the Panamera's guarantee is unaffected, irrespective of the number of racing starts the driver performs.
Accomplished – in nearly every respect
The PDK is a highly accomplished transmission system and is likely to meet with the approval of sportier drivers for whom the ultimate in low-speed urban smoothness is not an absolute priority; here, the PDK must concede some ground to the very best luxury-car planetary automatics. The start-stop system, too, could benefit from fine-tuning: the engine restarts almost instantaneously, but there is a slight lag before the transmission engages gear and propels the car forward.
The transmission feels much the same in all Panamera versions, whether two or four wheel drive, turbo or non-turbo. The same holds true for the sedan’s handling characteristics: even the rear-drive car is impressive on the track, turning crisply in to tight bends, cornering with excellent body control and minimal roll, especially with Sport mode selected.
On track, it is easy to forget that the Panamera is a car measuring nearly five meters and weighing just short of two tonnes. On public roads, however, its near two-meter width is more noticeable, especially in small villages and dense traffic. Reversing requires intrinsic trust in the back-up sensors and dashboard display: there is little rearward vision through the backlight.
The Turbo model has air suspension as standard, the others offering it as an option to steel springing. The steel-sprung car appears to ride more smoothly at low speeds but needs more use of the damper control to reduce unwanted softness at speed on undulating roads, especially straight roads; this introduces some harshness into the ride when the road surfaces are poor. The air suspension is less well resolved at urban speeds but comes into its own with reduced road noise and much better body control as speeds rise; the Sport and Sport Plus settings bring more road detail and some extra tautness, but the ride is still entirely acceptable.
Conclusion
The Panamera is a large and sophisticated luxury car with many layers of detail that take some time to penetrate. A single day's assessment, though intense, cannot possibly reveal the full depth of its abilities, which are clearly considerable. But what can be said, even at this early stage in the car’s career, is that the Panamera proves that a dual clutch transmission is indeed a credible solution for a high-end luxury car.
On the evidence of the four different cars we drove, Porsche's PDK application works very well under the majority of conditions and is especially satisfying for enthusiastic driving and track work. These are the qualities that will be the most important to typical Porsche customers, and in that sense the Panamera is well judged. Where the hyper-critical, especially those accustomed to large luxury sedans rather than responsive sportscars, may fault the PDK set-up is in certain aspects of its low-speed smoothness and, in particular, its hesitant restart. Knowing Porsche and transmission supplier ZF, however, these minor wrinkles will soon be ironed out – and in any case owners can always bypass the stop-start mode by keeping the selector in its Sports setting.
| Specification: Porsche Panamera | |||
|---|---|---|---|
Vehicle type: Four-door sports sedan |
|||
| S | 4S | Turbo | |
| Engine | 4.8-liter V8 | 4.8-liter V8 | 4.8-liter V8 turbo |
| Power | 400 hp (294kW) at 6500 rev/min | 400 hp (294kW) at 6500 rev/min | 500 hp (368 kW) at 6000 rev/min |
| Torque | 500 Nm at 6500 rev/min | 500 Nm at 6500 rev/min | 770 Nm at 4500 rev/min |
| Transmission | Seven-speed DC (opt), rear-wheel drive | Seven-speed DCT, four-wheel drive | Seven-speed DCT, four-wheel drive |
| Max speed | 283 km/h | 282 km/h | 303 km/h |
| 0-100 km/h | 5.4 sec | 5.0 sec | 4.2 sec |
| Fuel economy (lit/100 km) | 10.8 | 11.1 | 12.2 |
| Fuel economy (US mpg) |
20.9 | 20.4 | 18.5 |
| CO2 emissions | 253 g/km | 260 g/km | 286 g/km |
| Price on the road GBP | 72766 | 77269 | 95298 |
| Euro (Germany) | 94575 | 102251 | 135154 |
| USD | 89800 | 93800 | 132600 |
Story Filed: 9/24/2009
By Tony Lewin, managing editor DCTfacts.com