The eight-speed tiptronic is a classic torque-converter automatic transmission whose great strength lies in its high level of shifting and drive off comfort. Gear shifts are gentle, spontaneous, fast and highly flexible. Audi uses it in many models with a longitudinally mounted engine. Thanks to its eight speeds, jumps in rpm are small between gears, and the engine always runs near its ideal operating point. An rpm-adaptive torsion damper balances out undesired engine vibrations and enables efficient driving at extra-low engine speeds.
Also playing a large role in the efficiency ensemble is the torque converter lockup clutch with integrated damper. Under normal driving conditions, the lockup torque converter connects the transmission directly to the engine. It works with limited slip in certain situations, which – in interplay with the integrated damper – permits very low engine speeds without vibrations occurring. If the car is stationary, an internal clutch decouples the transmission from the engine, even if the “D” stage is still selected – this avoids losses due to oil circulation in the converter. As soon as the driver releases the brake, the clutch closes, and the damping effect of the torque converter ensures a smooth drive-off.
The dynamic shift program (DSP), which controls the eight-speed tiptronic, is housed in a small steel box within the gear-shift unit. It utilizes a fast processor. In the “D” mode, DSP autonomously sets the optimal shift point. To enable an efficient mode of driving, it gives preference to large gears and low engine speeds. In a second shift gate, the tiptronic allows manual intervention in the automatic transmission’s operation. This allows downshifting, e.g. on winding descents to boost engine braking or for driving in an exceptionally sporty style. In sport mode, the automatic transmission boosts driving dynamics by setting later shift points. The selector lever communicates fully electronically, without any mechanical connection with the transmission (shift-by-wire).
The eight-speed tiptronic is able to work together with the Audi start-stop system. It integrates a small, permanently filled hydraulic reservoir for this purpose. When restarting after a stop, its oil volume – of around 100 milliliters (0.1 US qt) – is pressurized by a spring-loaded piston, which is necessary for drive-off. The transmission is ready to start within a very short period of time.
In some Audi models the eight-speed tiptronic has an electric oil pump. It handles lubrication of the transmission and enables engagement of the gear that is needed for an engine restart after a coasting phase. Thanks to the mild hybrid technology, this makes it possible for the vehicle to shut off its engine during the drive when it is not needed for propulsion. When the vehicle is coasting and the engine is running in idle, a clutch is open in the area of the wheel sets. The transmission control unit detects stop-and-go situations and ensures very comfortable driving starts.