Audi's S tronic troika
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[06/17/2008] Audi now has three S tronic 'DSG' transmissions. We take a closer look at both the six- and seven-speed versions, as well as their origin in the fearsome S1 Rally car.
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Audi now has three S tronic 'DSG' transmissions. We take a closer look at both the six- and seven-speed versions, as well as their origin in the fearsome S1 Rally car.
For 2008 a new dual-clutch transmission is designed for use with longitudinally installed engines and quattro all-wheel drive, production is set for the second half of 2008.
Clutches: one is good, two is better
The seven-speed S tronic consists of two multidisc clutches, one operating engaging and disengaging even numbered gears – 2, 4, 6 and reverse – while the other, larger clutch, operates odd-numbered gears. All the gearwheels are mounted sequentially on the two output shafts, in the sequence 4, 6, 2, R, 1, 3, 7, 5.
Both part-transmissions are continuously active, but only one is connected to the engine at a time.
The shift process takes place as the clutches are operated – while one is opening, the other closes at lightning speed. This process takes only a few hundredths of a second and is completed without interrupting traction.
Quattro traction
Torque from the drive shaft is transferred to a self-locking centre-differential of the quattro drive train, which is able to deliver 85 percent of the power to the rear axle, or up to 65 percent to the front axle.
Carbon-coated synchronizer rings ensure synchronization of maximum quality and durability. Gears one through three and reverse have three-cone synchronization.
Transmission management is by means of a mechatronic module housing both control units and hydraulic actuators.
Efficiency is key, and the pressure needed in the control circuit is built up by an efficient gear-driven oil pump. When the car pulls off, cooling of the dual clutch by this pump is assisted by a suction-jet pump, ensuring oil delivery volume can be nearly doubled without any increase in drive power or drag.
Audi has designed the new seven-speed S tronic for a blend between performance driving and consistent economy. Featuring a maximum possible transmission-ratio spread of 8.0:1, provides for a performance biased, low first gear as well as a higher ratio for top gear cruising, blending low engine speeds and reducing noise whilst improving consumption.
The seven-speed S tronic is designed for engine speeds of up to 9,000 rpm and can transmit a torque peak of up to 550 Nm.
For Audi’s with a transverse engine layout there is a compact seven-speed S tronic. Here clutches do not run in an oil bath but are dry plate type jobbies.
The compacted seven-speed S tronic features a significantly lower torque threshold of only 250 Nm though.
Six-speed S tronic for compact models
Beyond the seven-speed S tronic for models featuring a longitudinally installed engine, Audi has S tronic for transverse installations too.
First seen in the spring of 2003 in the TT Coupé and Roadster, it was quickly transposed to the A3 too.
The six-speed S tronic differs as it uses a three-shaft layout to aid compactness. The dual transmission layout is enacted by a lay shaft housing odd-numbered gear ratios, whilst a secondary shaft houses the even-numbered gears.
Two clutches are arranged one behind the other and transmit power to two coaxial input shafts. Clutch 1 is linked to a solid shaft that acts as the input to part-transmission 1; clutch 2 drives the gears in part-transmission 2 via a hollow shaft surrounding the solid shaft. The six-speed tri-shaft S tronic transmission has a maximum torque threshold of 350Nm.
High performance certified
The first Audi with a dual-clutch transmission underwent initial tests in November 1985, in the Sport quattro S1 that Walter Röhrl drove in WRC events. Röhrl, the finest rally driver of his time and current Porsche chief test driver, described his 350 kW sports car as “a formidable thing”.
Taming the fearsomely quick S1 was a dual-clutch transmission controlled electrically by a short touch-action control lever in the S1.
A key engineering imperative here was to ensure traction was uninterrupted, thereby keeping the turbo on optimal boost.
A dual-clutch transmission was also installed in the S1 used during training for Röhrl’s suicidal 1987 storming of Pikes Peak, the notorious hill climb held in Colorado.
For 2008 a new dual-clutch transmission is designed for use with longitudinally installed engines and quattro all-wheel drive, production is set for the second half of 2008.
Clutches: one is good, two is better
The seven-speed S tronic consists of two multidisc clutches, one operating engaging and disengaging even numbered gears – 2, 4, 6 and reverse – while the other, larger clutch, operates odd-numbered gears. All the gearwheels are mounted sequentially on the two output shafts, in the sequence 4, 6, 2, R, 1, 3, 7, 5.
Both part-transmissions are continuously active, but only one is connected to the engine at a time.
The shift process takes place as the clutches are operated – while one is opening, the other closes at lightning speed. This process takes only a few hundredths of a second and is completed without interrupting traction.
Quattro traction
Torque from the drive shaft is transferred to a self-locking centre-differential of the quattro drive train, which is able to deliver 85 percent of the power to the rear axle, or up to 65 percent to the front axle.
Carbon-coated synchronizer rings ensure synchronization of maximum quality and durability. Gears one through three and reverse have three-cone synchronization.
Transmission management is by means of a mechatronic module housing both control units and hydraulic actuators.
Efficiency is key, and the pressure needed in the control circuit is built up by an efficient gear-driven oil pump. When the car pulls off, cooling of the dual clutch by this pump is assisted by a suction-jet pump, ensuring oil delivery volume can be nearly doubled without any increase in drive power or drag.
Audi has designed the new seven-speed S tronic for a blend between performance driving and consistent economy. Featuring a maximum possible transmission-ratio spread of 8.0:1, provides for a performance biased, low first gear as well as a higher ratio for top gear cruising, blending low engine speeds and reducing noise whilst improving consumption.
The seven-speed S tronic is designed for engine speeds of up to 9,000 rpm and can transmit a torque peak of up to 550 Nm.
For Audi’s with a transverse engine layout there is a compact seven-speed S tronic. Here clutches do not run in an oil bath but are dry plate type jobbies.
The compacted seven-speed S tronic features a significantly lower torque threshold of only 250 Nm though.
Six-speed S tronic for compact models
Beyond the seven-speed S tronic for models featuring a longitudinally installed engine, Audi has S tronic for transverse installations too.
First seen in the spring of 2003 in the TT Coupé and Roadster, it was quickly transposed to the A3 too.
The six-speed S tronic differs as it uses a three-shaft layout to aid compactness. The dual transmission layout is enacted by a lay shaft housing odd-numbered gear ratios, whilst a secondary shaft houses the even-numbered gears.
Two clutches are arranged one behind the other and transmit power to two coaxial input shafts. Clutch 1 is linked to a solid shaft that acts as the input to part-transmission 1; clutch 2 drives the gears in part-transmission 2 via a hollow shaft surrounding the solid shaft. The six-speed tri-shaft S tronic transmission has a maximum torque threshold of 350Nm.
High performance certified
The first Audi with a dual-clutch transmission underwent initial tests in November 1985, in the Sport quattro S1 that Walter Röhrl drove in WRC events. Röhrl, the finest rally driver of his time and current Porsche chief test driver, described his 350 kW sports car as “a formidable thing”.
Taming the fearsomely quick S1 was a dual-clutch transmission controlled electrically by a short touch-action control lever in the S1.
A key engineering imperative here was to ensure traction was uninterrupted, thereby keeping the turbo on optimal boost.
A dual-clutch transmission was also installed in the S1 used during training for Röhrl’s suicidal 1987 storming of Pikes Peak, the notorious hill climb held in Colorado.
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