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Porsche 911 manual shifts up a gear

Lucky number seven: Porsche has added an extra ratio to the 911's manual gearbox to help refinement and economy.

Seven-speed gearbox aims to improve Porsche 911 manual’s economy and refinement

19 Sep 2011

By BYRON MATHIOUDAKIS in FRANKFURT

PORSCHE says the world-first seven-speed manual gearbox in the all-new 991-series 911 makes it more on par with the PDK dual-clutch transmission.

In a scenario that might horrify traditional sportscar purists, the latter has dominated 911 sales since being launched in the previous-generation 997 Series II three years ago, accounting for as many as seven out of 10 orders.

According to 911 chief engineer August Achleitner, the original plan was to retain the old six-speed manual gearbox for the 991, until the decision was made to push boundaries by incorporating a seventh ratio in the interests of lower consumption and emissions.

“When we started the development of the 991, the decision had been opened as to whether to bring out a six-speed or seven-speed (manual transmission),” Mr Achleitner told Australian journalists at the Frankfurt motor show last week.

“We knew we had to create the new manual for the 991 out of the PDK layout, because that allowed for the extra wheelbase.

“(After building a number of prototypes we realised that) it made more sense to offer seven speeds.”

The move to seven speeds was made possible by basing the manual on the PDK transmission itself, which is already a seven speeder.

About 70mm of the 100mm wheelbase increase in the new 911 is due to the extra length afforded to the PDK, making the move to seven speeds for the manual possible.

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“You can use the long seventh speed for cruising along on the highways and so on, to reduce noise and fuel consumption,” Mr Achleitner said.

“So it makes sense. If you don’t want (to slot it up to seventh) you just operate it as a six speed.”

In the name of improved driveability and efficiencies, Mr Achleitner said the third and seventh gear ratios were shorter than the PDK, while top gear is an overdrive in the interest of quieter and more economical running.

As a result, buyers can choose to ignore seventh gear in urban situations, without fear of impacting on the performance on offer.

Although Porsche will not release the actual numbers until the 991 series is launched in November, it has revealed that every model in the new 911 range has a Euro cycle combined average fuel consumption figure of under 10 litres per 100km for the first time, while the 0-100km/h acceleration times on all versions have decreased compared with the outgoing car.

The seven-speed manual’s shift pattern is identical to that of a normal six-speed manual, except that ratio number seven is on the extreme right and up, while reverse gear is on the extreme left and up.

PDK, an acronym for the German word ‘Doppelkupplungsgetriebe’ that literally means ‘dual clutch gearbox’, dates back nearly 30 years to when Porsche first developed the system for its successful motor racing program – although its production car application began in earnest for the 911 (and subsequent models) in the late 1990s.

Co-devised with specialists ZF, PDK is completely different from Volkswagen’s DSG dual clutch gearbox, and departs from a conventional torque converter automatic transmission by being a full manual gearbox that comprises two clutches that activate two separate sets of pre-selected gear ratios.

Porsche expects the new manual gearbox to claw back some of the ground it has lost to PDK over the last few years.

The sales split was more even when the 911 offered the old five-speed Tiptronic automatic as an alternative to the six-speed manual before 2008.

“We had a dramatic change with the manual to the PDK compared to the old automatic transmission,” Mr Achleitner said.

“Today, we have about 70 per cent ordering the PDK. (Previously) it was never more than 50 per cent.”

Following the global launch in America, 991-series sales commence in December, followed by the Australian release in March.

Prices will kick off from $229,900 for the base Carrera with the 257kW 3.4-litre flat-six engine and seven-speed manual, and $263,100 for the 294kW Carrera S 3.8-litre manual.

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