First look: PDK and DFI for facelifted Porsche 911

PORSCHE has revealed the facelifted 911 coupe and cabriolet ahead of its global media launch in Stuttgart next week and its Australia release on September 20, when local pricing will be announced.

True to the iconic sports car maker’s engineering traditions, Zuffenhausen’s 997-series midlife model upgrade emerges - just months after the local launch of the final 997-911 variant, the GT2 - as a technical tour de force rather than a cosmetic makeover.

As has been widely expected for some time, the revised two-door flagship brings together, for the first time in a Porsche, the twin fuel consumption reduction technologies of direct petrol injection and a double-clutch transmission (DCT).

Making its debut on both flat-six boxer engines that power the 911, direct-injection brings significant advances in both performance and fuel economy – just like the optional new Porsche-Doppelkupplung (PDK) automated manual gearbox, which finally replaces Porsche’s aged five-speed Tiptronic S automatic.

Porsche says PDK combines the driving comfort of an automatic transmission with the dynamic gearshift of a sequential racing gearbox.

“PDK improves the car’s acceleration and reduces fuel consumption to a level even lower than before,” says Porsche, whose development drivers “benefited from the double-clutch system which allowed them to shift gears without the slightest interruption of traction and pulling power, while at the same time keeping both hands on the steering wheel.

The move will see the 911 join direct rivals like Nissan’s new GT-R (here in early 2009) and BMW’s M3 M-DCT (due on sale this month) in offering a self-shifting sequential manual.

But while the BorgWarner-developed rear transaxle unit in the GT-R has six speeds, the 911 joins the M3’s Getrag-sourced unit with seven – and also matches its launch control function, albeit as part of the optional Sport Chrono Plus package.

Ironically, Porsche first devised its dual-clutch transmission system 25 years ago for the racetrack and has worked on its shift speed smoothness ever since. PDK was widely expected to debut in the Cayman coupe and then the current 911 Turbo launched here in 2006, but similar transmissions have been available since 2003 and are now widespread in models from the Volkswagen Group, in which Porsche AG now has a majority shareholding.

In Europe this year VW released a second-generation, seven-speed version of its acclaimed Direct Shift Gearbox (DSG called S tronic by Audi), which continues to employ DualTronic twin-clutch technology first productionised by Detroit’s BorgWarner. The first VW Group models to feature a seven-speed DCT in Australia will be Audi’s new A4 and Skoda’s new Superb, both due here in the first quarter of next year.

The same technology is also shared with German transmission rival Getrag, which in addition to co-developing the M3’s seven-speed M-DCT with BMW, also supplies six-speed DCTs to Mitsubishi for its new Lancer Evo (due on sale in July), Chrysler for turbo-diesel versions of its Dodge Journey, Sebring and Avenger (here from September) and Ford/Volvo for some S40/V50 models not yet slated for Australia.

Porsche AG drivetrain expert Dr Erhard Moessle told GoAuto in August 2006 that at that stage PDK offered weight and shift-speed advantages over a traditional torque converter-equipped automatic transmission, but did not yet match its smoothness or strength.

“Double clutch is lighter and faster than a torque converter and you can put more speeds in it, but it’s not as comfortable for 90 per cent of driving and we may have risked losing some customers. Also, in VW it handles only up to 320Nm, but we need it to handle 700Nm.”

It appears Porsche has overcome these hurdles to offer its first production models ever with a PDK DCT, which differs from a conventional automatic, a conventional manual and a continuously variable transmission (CVT) by being a fully manual gearbox with two clutches that electronically activate two separate sets of pre-selected gear ratios.

It can be used in fully manual or automatic modes, and is both quicker and smoother than a single-clutch sequential manual gearbox (SMG) as found in the M5 and previous M3.

Direct-injection is also common in many modern diesel and now petrol engines, including from Audi under the FSI name, which is employed on the VW-built V6 that powers Porsche's entry-level Cayenne, introduced here in March 2007 as part of a facelifted SUV range that also included the fitment of direct-injection to V8 variants.

The first direct fuel-injection (DFI) versions of Porsche’s famed flat six appear in the entry-level 911 coupe and cabriolet, in both rear-drive 3.6-litre Carrera and 3.8-litre Carrera S guises. Revised Carrera 4 models are yet to appear.

Maximum power output for the base 911 engine is up by 15kW, from 239kW to 254kW, while the Carrera S flat-six now produces 283kW – up a substantial 22kW from 261kW.

The (3.8) Carrera S Coupe’s extra top-end engine performance now gives it a top speed of just over 300km/h, almost matching the previous-generation GT3 and Turbo flagship 911s.

Porsche says that with the seven-speed PDK transmission, the new (3.6) 911 Carrera Coupe can return average fuel consumption of just 9.8 litres per 100km and produce up to 15 per cent less CO2 emissions.

What’s more, the same vehicle can blast to 100km/h in a claimed 4.5 seconds – 0.2 seconds quicker than the conventional six-speed manual version. Activating the optional launch control system reduces that by a further two-tenths, to 4.3 seconds.

That's within about half a second of the top-shelf 911 Turbo, which does the 0-100 sprint in 3.9 seconds as a manual and 3.7 seconds as an auto - and undoubtedly quicker again as a PDK.

Apart from their cleaner, more frugal and more powerful engines, mated to a more effective and efficient alternative to the standard six-speed manual, the facelifted 911 coupe and cabrio also score subtle cosmetic updates.

They include modified front and rear bumpers, and new headlights that now comprise daytime LED driving lights and bi-Xenon beams as standard across the range. Dynamic Bending Lights also join the 911 options list.

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