November 22, 2002

Audi TT 3.2 quattro With New Automatic Sports Transmission (DSG)
Text and photos courtesy of Audi AG

Audi is unveiling the first version of its TT Coupé sports car to feature a 3.2-litre six-cylinder engine and completely new transmission technology. The combination of the high-torque 3.2-litre engine with 250 bhp and innovative sports gearbox emphasises the dynamic drive qualities of the four-wheel-drive TT in a unique way.

The revolutionary Direct Shift Gearbox (DSG) transmission successfully combines all the benefits of a conventional six-speed manual gearbox with the qualities of a modern automatic version. The driver thus benefits from enormous agility, driving enjoyment and economy as well as convenient operation and smooth acceleration with uninterrupted traction.

The source of the power is the proven 3.2-litre V6 engine. With its cylinder angle of 15 degrees, it is extremely compact and is therefore especially suitable for installation transversely to the direction of travel. The valve control process generates only little friction thanks to the use of roller cam followers with hydraulic adjustment. The compression ratio is 11.3:1.

Other technical details such as continuously adjustable inlet and exhaust camshafts and the variable intake manifold give the six-cylinder engine superior torque and power output, coupled with low emissions. A great deal of detail work has once again been invested particularly in this area in order to improve still further on its peak output and torque characteristic specifically in the TT. The engine now delivers 184 kW (250 bhp) and a broad peak-torque range with a maximum value of 320 Nm from 2,800 to 3,200 rpm.

Throttle valve actuation is designed for an exceptionally agile, spontaneous engine response to accelerator pedal movements. The way it interacts particularly with the ultra-rapid, precise control technology of the new twin-clutch transmission opens up an entirely new dimension in propulsive power.

The sound of the dual-branch variable exhaust system suitably reflects these sporting characteristics. A flap in the exhaust system is opened or shut depending on engine speed. Its sonorous sound never becomes over-assertive, even at high engine speeds, yet it unmistakably conjures up all the sentiments that sports-minded TT drivers appreciate.

The Audi TT 3.2 accelerates from 0 to 100 km/h in just 6.4 seconds, whilst the top speed is gently governed at 250 km/h. The overall consumption is just 9.8 litres over 100 km (provisional figure): a value that stands comparison even with vehicles with a classic 6-speed manual gearbox. The differences compared with the conventional geared automatic transmission with torque converter are even more impressive, since the latter is prone to significantly higher transmission losses due to its fundamental concept.

     

The new Direct Shift Gearbox (DSG)

So how does this revolutionary transmission concept work? The basis for the new development is a 6-speed manual gearbox with high variability in the selection of the transmission ratio. Thanks to the use of an integrated twin multi-plate clutch with ingenious control system, two gears can be engaged at the same time. During dynamic operation of the car, one gear is engaged. When the next gearshift point is approached, the appropriate gear is preselected but its clutch kept disengaged. The gearshift process opens the clutch of the activated gear and closes the other clutch at the same time. The gear change takes place under load, with the result that a permanent flow of power is maintained.

The technology of this twin-clutch transmission, the only one of its kind in the world, has its roots in motor racing. As far back as 1985, Walter Röhrl successfully tested it in his Audi Sport quattro S1.

Today, the new design satisfies the exacting requirements of convenient gear-shifting and maximum operating life for everyday use in series production vehicles. This transmission has been developed at group level and is built at the Kassel transmissions plant. This compact transmission is capable of handling torque of up to 350 Newton-metres.

The control logic integrated into the transmission casing maintains optimum gearshift strategies that perform lightning-fast gearshifts that are nevertheless smooth and almost jolt-free. The driver can directly influence the gear selected and the gearshift timing at will, by means of the gear lever in the manual gate or the standard-fit shift paddles on the steering wheel.

In the automatic mode, the driver can shift from position D to the ultra-sporty S program, in which upshifts are retarded, downshifts advanced and the shifting process accelerated. A remote one-touch function accessed via the shift paddles on the steering wheel in addition temporarily calls up the manual mode even in automatic modes D and S.

High overall efficiency is thus combined with superlative road performance and ease of control to produce an exceptional drive concept. The user interface is reminiscent of the familiar gearbox gate of the Audi tiptronic or multitronic.

     

High tech in very confined conditions

As on conventional manual gearboxes, the transmission ratios are present on input and auxiliary shafts in the form of pairs of toothed wheels. In contrast to manual gearboxes, the input shaft is divided into two sections. It comprises an outer hollow shaft, and an inner shaft. The 1st, 3rd, 5th gears and reverse are located on the inner shaft. The hollow shaft handles the even-numbered gears.

Each of these shafts is selected by means of a separate multi-plate clutch running in oil. The two electronically controlled, hydraulically actuated clutches are packed inside each other for maximum space economy.

As well as their high efficiency and ability to transmit high torques, clutches of this type permit a wide range of starting characteristics. In other words, the multi-plate clutch can be controlled in such a way that every conceivable form of pulling away is possible, from an ultra-gentle edging along on a slippery surface to sports-style acceleration at full throttle.

The gearshifts it produces feel spontaneous and decisive, as if executed at the push of a button. The electronic-control throttle blip feature of the manual and S modes reinforces the impression of ultra-dynamic gearshifts.

A shift-by-wire control concept has been implemented. The mechatronic concept combines a control unit with an electro-hydraulic control unit. The resulting device is housed in the upper section of the transmission casing. The signals from ten individual sensors are processed centrally there, and the actuation values calculated using the relevant information on the momentary driving situation from the drive CAN bus. The application pressure of the two clutches is regulated by special solenoid-operated valves depending on the situation, and the gear positioners operated.

The electronics also calculate which additional gear is to be preselected by the corresponding positioning cylinder and selector forks, and manages all actuating elements and the oil cooling circuit via six pressure regulation valves and five on/off valves.

All in all, the entirely new concept results in a decidedly agile performance, with the added benefit of the typically low fuel consumption of an advanced 6-speed manual gearbox.

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