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Porsche twin-clutch near
Porsche's 911 Turbo misses out on a PDK double-clutch gearbox - but stay tuned...
18 Aug 2006
THE project leader for the new 911 Turbo – and the remainder of Porsche’s all-wheel drive 911 range – has admitted he wanted to launch the company’s new flagship with a double-clutch transmission rather than a traditional, albeit vastly upgraded, five-speed auto.
Along with direct petrol injection, a double-clutch transmission is the most widely anticipated future technology Porsche has admitted to developing – since the company invented the revolutionary gearbox, known as PDK, for the racetrack some 20 years ago.
Since then the Volkswagen Group, in which Porsche has a 20 per cent stake, has released its version, dubbed DSG, in a variety of VW and Audi models. But the expected debut of PDK in Cayman and then the 997-series 911 Turbo appears to have been delayed.
"It was not planned to launch PDK, but I would like to have had a double-clutch gearbox in the 911 Turbo," 911 all-wheel drivetrain boss Dr Erhard Moessle told GoAuto. He said PDK offered weight and shift-speed advantages over the traditional automatic transmission it will eventually replace, but did not yet match the torque converter-equipped auto’s 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." Longevity has always been a focus of Porsche, which says its drivers average around 12,000km a year, compared to about 4000km for the average Ferrari owner.
While PDK – rather than SMG, CVT or a six-speed auto, which will not fit in 911 – remains on Porsche’s new model horizon, the new 911 Turbo "makes do" with an extensively upgraded version of the factory’s five-speed Tiptronic S auto – alongside the 911T’s standard six-speed manual. Upgrades include a "Fast-Off" function, which keeps the 911 Turbo in its selected gear when throttle pressure is eased significantly (previously this could only be achieved by releasing the throttle completely before applying it again rapidly), and a new "Fast-Back" function, which drops to the next lowest gear when throttle is released rapidly and brakes are applied within 1.5 seconds.
Apart from bringing a big price reduction for other 911 auto variants, the result is the first automatic Porsche that’s quicker than its manual sibling, thanks mainly to the fact that the new 911T, which employs a world-first variable-geometry turbo in a petrol engine, produces maximum torque (620Nm) at just 1950rpm – about the same engine speed that torque converter lock-up occurs.
Not only in the new 911 Turbo just five seconds lower around the Nurburgring than the manual in the hands of Walter Rohrl (7:49 v 7:54, compared to a Ferrari S430 at 7:55), the auto sprints to 100km/h two-tenths quicker than the manual, and 1.1 seconds quicker than its predecessor. Both cars have a claimed top speed of 310km/h and Porsche says a 0-200km/h time of 12.2 seconds (12.8 for the manual) makes 911T the best in the supercar class.
"We are normally very conservative at Porsche, but you can be sure that every driver can do a 3.7 (0-100km/h pass) in the auto 911 Turbo. But maybe not every driver can do a 3.9 in the manual," Dr Moessle said.
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