The Audi Q5 SUV will be launched in Australia next month and will showcase yet another of the brand’s extremely progressive technologies – the seven-gear S tronic transmission.
This latest evolution in transmission technology offers an extremely dynamic, highly-efficient action. Designed for use, for the first time, with a longitudinally-installed engine and quattro all-wheel drive, this dual-clutch transmission will be suited to a wide range of sporty models – the latest being the new Audi Q5. The 7-speed S tronic was previously only available for transverse-mounted engines found in the Audi TT and A3 models.
It is a high-tech component which Audi has designed to be both dynamic and highly efficient, another clear measure in Audi’s progressive performance strategy.
Audi Q5 drivers are able to use the new seven-speed S tronic in various modes. The fully automatic mode, in which the control unit determines the gearshifts, offers the D (Drive) and S (Sport) programs. Gears can also be changed manually with the selector lever or with the shift paddles on the steering wheel (standard for V6 models) – an amazingly fast affair. The result is a gearshift that is dynamic, comfortable and very precise – typically Audi.
The seven-speed S tronic is composed of two transmission structures. It integrates two multi-plate clutches that control different gears. The large K1 clutch located on the outside directs the torque via a solid shaft to the gear wheels for the odd-numbered gears 1, 3, 5 and 7. A hollow shaft rotates around the solid shaft and is connected to the smaller K2 clutch, which is integrated into the inside of its larger sibling, and which controls the gear wheels for the even-numbered gears 2, 4 and 6, as well as reverse gear. All gear wheels are arranged one behind the other on both output shafts, in the order 4, 6, 2, R, 1, 3, 7 and 5.
Both transmission structures are continuously active, but only one is connected to the engine at any one time. For example, when the driver accelerates in third gear, the fourth gear is already engaged in the second transmission structure. The shifting process takes place as the clutch changes – K1 opens and K2 closes.
This highly-sporty set-up means that gear change takes only a few hundredths of a second and occurs with no interruption to traction. It is so fluid and smooth that the driver hardly notices it.
In the Audi Q5, power flows from the drive shaft to the self-locking centre differential of the quattro drivetrain, which distributes it into two directions. In the regular distribution pattern, 60 percent of the torque flows via the propeller shaft to the rear-axle differential and 40 percent via a side shaft to the bevel pinion of the front-axle differential. To reduce weight, this shaft is also hollow. When needed, the centre differential can deliver up to 85 percent of the power to the rear axle or up to 65 percent to the front axle.
Transmission management is by means of a mechatronic module. This compact unit containing the control units and hydraulic actuators is a completely new development. Its control concept allows the speed of the gearshift to be varied, with extremely precise control of the power necessary for the process.
The control pressure is generated by an efficiently operating oil pump that is located next to the mechatronic module and is driven by a gear stage. It is supported by a vacuum booster for cooling the dual clutch during starting.
This virtually doubles the amount of oil delivered on demand, without any need to increase the power consumption.
Audi has designed the new seven-speed S tronic for exhilarating driving and consistent economy. The new high-tech unit is notable for its very high efficiency. Its highly intelligent controls also permit economical driving in the automatic mode. The maximum possible transmission-ratio spread of 8.0:1 provides a sporty, low transmission ratio for the first gear as well as a high ratio for top gear as a means of keeping engine speed low. The new transmission therefore suits modern TDI, FSI and TFSI engines with their high torque even at low engine speeds.
The seven-speed S tronic is designed for engine speeds of up to 9,000 rpm and can transmit a torque of up to 550 Nm.
In other words, this utterly new transmission is ideal for mid-range engines, delivering lightning-fast gear changes, uninterrupted power flow and yet is highly efficient and sporty at the same time.
“Vorsprung durch Technik”: background to S tronic
Audi has led the field in transmissions for many years. The introduction of quattro all-wheel drive in 1980 was a milestone in the history of automotive technology, and S tronic is a prime example of the company’s basic claim to leadership in this area.
The first Audi with a dual-clutch transmission underwent initial tests as long ago as November 1985, in the Sport quattro S1 that Walter Röhrl drove in World Rally Championship events with Christian Geistdörfer as his navigator. Röhrl, the finest rally driver of his time, described his 350 kW (476 hp) sports car as “a formidable thing” and a “natural phenomenon,” and the high-tech transmission provided him with even more powerful performance.
The dual-clutch transmission, which was controlled electrically by a short touchaction control lever in the S1, could shift through its five gears at lightning speed. Since traction was not interrupted, there was no loss of boost pressure from the five-cylinder engine’s turbocharger. A dual-clutch transmission was also installed in the S1 in 1987 during training for Röhrl’s victorious storming of Pikes Peak, the hillclimb held in Colorado.
Leave a comment