• Comment by
  Daniel McCoey
• July 19, 2008 @ 12:39 pm

Happy to oblige with a technical explanation Steane.

The PDK is an automated manual transmission capable of executing lightning-quick up-shifts with no drop-off in engine power. So it’s important to note it really is a manual Box and not an Auto which many people make the mistake of given the similarity to an auto box with only two pedals. The PDK features both a console-mounted shifter and steering wheel paddle shifters and offers manual and fully automatic modes.

The Twin Clutch PDK puts odd (1st, 3rd, 5th,7th ) and even (2nd, 4th and 6th) gears on separate input shafts, each connected to an individual clutch. With both clutches under precise system control, this arrangement allows lightening-fast, smooth and lag-free gear changes with no interruption in power delivery. Using clutches instead of a torque converter to transmit power makes the PDK simpler in structure and reduces power transmission losses for higher transmission efficiency that leads to improved fuel mileage.

In the P or N range, 1st and 2nd gears are engaged with each clutch free status as preparation (Pre-selection). During driving, the next up shift gear is engaged with clutch free status for next gear preparation. When driver turns off the IG, the engine will run for approximately 2 seconds to disengage 1st and 2nd gears. The implementation of “Launch Control” however is a different kettle of fish all together as when a pre-subscribed amount of revs are met, then the clutch disengages and then takes up when the brake is released in 1st gear.

When driving in 1st gear The even number gear clutch is kept released, and the 2nd gear is engaged in advance. When in an even number gear, the odd number gears are
engaged in advance.

When driving in 2nd gear the clutch for the odd number gears is released at the shifting timing in accordance with the shift mapping in the PDK ECU and the drive mode
selection. The clutch (for even number gears) is engaged to perform driving in 2nd gear.

Because the shifting is performed only by the alternation of two clutches, the shift time is short, and there is always drive from one of the clutches, thus reducing drive loss during gear changes.

It’s also important to note that rollback while on a hill is a characteristic of the PDK due to the use if the twin clutch platform, so it’s not an inherent design flaw but a byproduct of this technology, so nothing is wrong with your car if you experience this phenomenon.

Clear as mud?