[AshSimmonds]

http://www.drive.com.au/Editorial/ArticleDetail.aspx?articleID=53775&IsPgd=0

Porsche PDK - New double-clutch gearbox in detail

If you want the fastest Porsche 911 on the market then you’ll have to pay extra for the new automatic transmission, known as PDK.

The more efficient PDK gearbox produces faster shifting times that make PDK-equipped 911s quicker than their manual counterparts. But they’ll bring a price premium of about $6500.

The new PDK transmission also includes a seventh gear designed purely for reducing fuel consumption at freeway speeds.

Porsche refers to the PDK – in German it stands for Porsche doppelkupplungsgetriebe and translates to Porsche double-clutch – as an automated manual, but to the driver it operates as a regular automatic.

Replacing the Tiptronic transmission in the Porsche sports car line-up, the PDK uses two clutches for significantly lower gearshift times. Combined with all-new engines for the 911 it leads to significantly faster acceleration times.

Similar in principle to the Volkswagen DSG system that pioneered the increasingly popular twin-clutch technology in road cars, Porsche’s PDK was first used on a Porsche race car in 1983.

Porsche’s new PDK transmission is more efficient than a regular automatic because it’s effectively a manual gearbox with two computer controlled clutches. Unlike a regular automatic, such as the Tiptronic system PDK replaces, PDK has no torque converter.

The first, and largest, of the two clutches in the Porsche PDK system selects reverse, first, third, fifth and seventh gears (R, 1, 3, 5 and 7).

The second clutch – which actually sits inside the diameter of the larger first clutch – selects second, fourth and sixth gears (2, 4 and 6).

When starting off from a standstill, first gear is engaged while second is already preselected, ready to be almost instantly engaged by the second clutch.

Once second gear is selected third gear is then preselected ready for another gearchange in just a few hundredths of a second.

Available for now on the new Porsche 911 the PDK transmission will also be fitted to the smaller Boxster and Cayman models as well as the upcoming Panamera.

Porsche says the Cayenne off-road wagon will continue with the Tiptronic – a regular automatic transmission – because it’s better suited to the style of vehicle.

Porsche’s PDK transmissions improve straight line acceleration through the benchmark 0-100km/h test by as much as 19 per cent.

PDK-equipped 911s are now as much as 0.4 seconds quicker to 100km/h than 911s with a manual gearbox and exactly the same engine output.

Compared with the original 997-generation 911, the second-generation 997 is around 0.1 seconds quicker to 100km/h due to the more powerful engines.

However, 911s fitted with the new PDK transmission are up to a full second quicker to 100km/h than the Tiptronic equipped models they now replace.

The PDK transmission has also allowed Porsche to let the revised engines rev slightly higher, for added performance, noise and drama.

As part of the PDK package Porsche added a seventh gear, chosen specifically for fuel consumption, a major thrust with the new 911 and Porsche’s moving forward.

All Porsche 911s reach their maximum speed in sixth gear. The seventh gear is used only when cruising at speeds above about 70km/h.

For even better performance the Porsche PDK transmission can be optioned with a Sports Chrono Package Plus kit.

The Sport Chrono pack brings a chronograph lap timer as well as added software for the gearbox that allows even faster, more aggressive gear changes and a Formula One-style launch control function that makes for faster take-offs.

Accompanying the PDK gearbox is a regular automatic gear selector with Park, Reverse, Neutral and Drive settings.

As with many modern automatics the lever can be shifted to the side to allow sequential gear changes by tapping the lever forward (upchange) and back (downchange). There are also buttons on the steering wheel that do the same thing but allow the driver to leave their hands on the wheel during changes.

PDK can be driven in three modes: regular, Sport and Sport Plus (the latter only available on cars fitted with the optional Sports Chrono Package Plus system).

The distinguishing features of each PDK mode are:

Regular
- smoother, more relaxed gear shifts with almost imperceptible changes
- maximum fuel efficiency
- greater propensity to use higher gears

Sport
- sharper, more aggressive gear changes
- increased throttle sensitivity, so you don’t push the accelerator as hard

Sport Plus
- fastest, most aggressive gear changes
- holds lower gears and higher engine revs for more instant response
- increased throttle sensitivity, so you don’t push the accelerator as hard
- F1-style launch control function
- stability control allows more aggressive driving before intervening

Porsche Australia boss Michael Winkler expects the PDK transmission to account for around 70 per cent of 911 sales; currently around half of all Porsche sports cars sold are automatics.

While Winkler admits it’s difficult to predict how many people will choose the automatic PDK 911, the fact it’s quicker and more economical would suggest it will easily be the more popular transmission.

911 performance: Manual v auto and Tiptronic v PDK
(0-100km/h for Porsche 911: new v old)


                                                2nd generation 997 911                      Original 997 911

911 Carrera manual                            4.9 seconds                              5.0 seconds
911 Carrera auto                                  4.7 seconds                              5.5 seconds
911 Carrera auto Sport Chrono         4.5 seconds                              n/a
911 Carrera S manual                         4.7 seconds                              4.8 second
911 Carrera S auto                               4.5 seconds                              5.3 seconds
911 Carrera S auto Sport Chrono      4.3 seconds                              n/a


Porsche 911: the models of 997 second generation

Porsche 911 Carrera Coupe

Engine: 3.6-litre horizontally opposed six-cylinder
Power: 254kW at 6500rpm
Torque: 390Nm at 4400rpm
Weight: 1415kg (manual), 1445kg (PDK)
Gearbox: Six-speed manual or seven-speed PDK automatic
Fuel consumption: 10.3L/100km (manual), 9.8L/100km (PDK)
0-100km/h: 4.9 seconds (manual), 4.7 seconds (PDK), 4.5 seconds (PDK with Sport Chrono)
Top speed: 289km/h (manual), 287km/h (PDK)


Porsche 911 Carrera S Coupe

Engine: 3.8-litre horizontally opposed six-cylinder
Power: 283kW at 6500rpm
Torque: 420Nm at 4400rpm
Weight: 1425kg (manual), 1455kg (PDK)
Gearbox: Six-speed manual or seven-speed PDK automatic
Fuel consumption: 10.6L/100km (manual), 10.2L/100km (PDK)
0-100km/h: 4.7 seconds (manual), 4.5 seconds (PDK), 4.3 seconds (PDK with Sport Chrono)
Top Speed: 302km/h (manual), 300kmh (PDK)


Porsche 911 Carrera Cabriolet

Engine: 3.6-litre horizontally opposed six-cylinder
Power: 254kW at 6500rpm
Torque: 390Nm at 4400rpm
Weight: 1500kg (manual), 1530kg (PDK)
Gearbox: Six-speed manual or seven-speed PDK automatic
Fuel consumption: 10.4L/100km (manual), 9.9L/100km (PDK)
0-100km/h: 5.1 seconds (manual), 4.9 seconds (PDK), 4.7 seconds (PDK with Sport Chrono)
Top speed: 289km/h (manual), 287km/h (PDK)


Porsche 911 Carrera S Cabriolet

Engine: 3.8-litre horizontally opposed six-cylinder
Power: 283kW at 6500rpm
Torque: 420Nm at 4400rpm
Weight: 1510kg (manual), 1540kg (PDK)
Gearbox: Six-speed manual or seven-speed PDK automatic
Fuel consumption: 10.8L/100km (manual), 10.3L/100km (PDK)
0-100km/h: 4.9 seconds (manual), 4.7 seconds (PDK), 4.5 seconds (PDK with Sport Chrono)
Top speed: 302km/h (manual), 300km/h (PDK)