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Audi R8 Supercar Makes the Switch from AMT to Dual Clutch

September 23, 2012

Sports enthusiasts have always had high regard for the mid-engined Audi R8 supercar, launched in 2006. Since that date the R8 has expanded from a single model to four, with a choice of V8 or V10 engines and coupé or open-topped Spyder body styles. And in that intervening period Volkswagen has taken control of Porsche, meaning that the R8 has become a corporate stablemate to the Porsche 911 rather than its younger rival.

But while the praise for the R8 has been pretty well unanimous, even from committed Porsche fans, there was one aspect – albeit an optional one – of the model that received an unaccustomedly cool reception. While the six-speed manual transmission drew no particular comment, its automated R tronic alternative was dismissed as disappointing or, in one influential review, summed up as “the optional semi-automatic gearbox is expensive and jerky at low speeds, but that’s about as far as the complaints go.”

All that now stands to be put right with the just-announced second generation R8. Again, there is the choice between a 4.2 liter V8, giving 430 hp at 7,900 rpm, and the 5.2 liter V10, good for 525 hp at 8,000 rpm in its standard form and a mighty 550 hp in the new flagship version, the R8 V10 Plus. The six-speed manual transmission is standard on the V8 and optional on the V10, while the new seven-speed S tronic dual clutch transmission is optional on the V8 and standard on the V10.

The seven-speed S tronic transmission is a new design, says Audi. Though cutaways and full technical details have yet to be revealed, the company does say that the gearbox is an unusually compact design using three shafts and measuring less than 60 cm axially. An unusual feature of its architecture is the fact that the two clutches are not nested concentrically, as is the usual practice, but located one behind the other. No explanation has yet been stated for this, but one possible reason is to provide two full-sized clutches and to avoid the high temperatures that can often build up in the smaller inner clutch of a conventional nested DCT clutch design.

As with most sporting DCT applications, the R8’s S tronic can be controlled by the center selector lever or steering wheel mounted shift paddles. A sports mode and launch control are offered, though Audi does not give details of how these operate.

All versions of the R8 have quattro four-wheel drive, with the propeller shaft for the front wheels running forwards through the crankcase to the front differential, where a viscous coupling directs around 15 percent of the torque to the front. Should the rear wheels spin, a further 15 percent of torque can be allocated to the front axle, and a mechanical differential lock operates on the rear axle.

The company states enigmatically that the “final drive position has a wide gear ratio”, perhaps indicating a tall seventh gear for economical and restful cruising. However, travel aboard the R8, in any of its guises, is unlikely to be restful: even in its V8 form it accelerates to 100 km/h (62 mph) in 4.6 seconds with the manual transmission. Specifying the DCT option trims 0.3 seconds off that time – just as it does with the V10 model, hitting 100 km/h in 3.8 seconds. The top-performance V10 Plus hits the 100 mark in just 3.5 seconds.

All five models comfortably exceed 300 km/h (186 mph), and the efficiency of the seven-speed S tronic transmission is shown in the fuel consumption returns: the top R8 V10 Plus achieves 12.9 liters per 100 km (18,23 US mpg) as a DCT automatic but 14.9 liters per 100 km (15.79 US mpg) with the manual transmission.

In Europe the R8 range is priced between €113,500 and €173,200; North American prices have not yet been announced.

The launch of the new R8 at the end of this year will bring to eight the tally of advanced and high performance transmissions built by the Volkswagen group. To the new mid-engined R8’s DCT must be added the seven-speed inline S tronic DCT for front engined Audis and the high-torque transversely mounted S tronic for the Audi S3 and TT RS sports models; Volkswagen, Audi, SEAT and Skoda use both the six-speed wet clutch and seven speed dry clutch DSGs for transverse applications, and Porsche has two DCTs of its own – the three-shaft, seven speed PDK for the rear-engined Boxster and 911 Carrera and a two-shaft version for the Panamera luxury sedan. Lamborghini, finally, uses a new quick-shifting seven-speed AMT in its Aventador supercar but is expected to move to an as-yet unspecified DCT when it launches its extreme SUV later this decade.

© 2013, The Lubrizol Corporation



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