The six-speed tiptronic automatic transmission will be available as an alternative to the manual gearbox for 3.2 FSI quattro versions from April 2008 onwards, and for the 3.0 TDI quattro later in the year. The design of this classic automatic transmission, with Sport program and additional manual-shift mode, has been thoroughly revised, with particular attention being paid to the transfer-case and torque-converter.
The torque converter is now equipped with a new two-stage torsional vibration damper that enables the lock-up clutch to remain engaged for long distances. This boosts overall efficiency and reduces the car’s fuel consumption. When the car is at a standstill, a controlled drive-off clutch disconnects the transmission from the engine even if the selector lever remains in position D. This clutch is engaged as soon as the driver releases the brakes.
The latest generation tiptronic transmission reacts more rapidly and performs much faster shifts without any sacrifices in refinement. These improvements are due to an improved layout of the oil passages used to fill the converter, and more powerful software for the Dynamic Shift Program (DSP), which uses an adaptive operating principle. During an upshift the control unit now lowers engine torque by as much as 80 per cent, and during a downshift it opens the throttle for a predetermined time.
At launch in the UK the multitronic continuously variable transmission is fitted exclusively to the A4 2.7 TDI. During 2008 it will also become available for the 1.8 TFSI and 2.0 TDI. It combines the advantages of a manual gearbox with those of a conventional automatic transmission with torque converter. With its high efficiency and widely spread ratios, multitronic ensures that the engine runs in its optimal operating range whenever possible and thus keeps fuel consumption low. Internal losses have been reduced still further by improvements to component geometry, the shaft bearings and the design of the oil pump.
The multitronic’s new variator permits a wider spread of transmission ratios: 6.73 instead of the previous 6.25 between the highest and lowest ratios. The lowest ratio permits strong acceleration, whereas the highest enables the engine’s fuel-saving potential to be fully utilised even at low engine speeds. The drive-off ratio has been lowered so that the A4 sets off more rapidly from a standing start. The multitronic transmission has an adaptive control system that varies its settings according to driving style and road topography.
In the D mode, the effective transmission ratio changes steplessly, but a button can also be pressed to activate the dynamic Sport program, which selects lower ratios in all circumstances. When accelerating, the fixed characteristics of the Dynamic Shift Program select eight specific ratios in succession. The third operating mode has provision for manual selection of these eight fixed ratios by the driver, either via the selector lever or as an optional extra using shift paddles behind the steering wheel.Published 9 February 2008