PDK documentation on the S1

[Dave.Eaton]

probably the best description is reading jeremey walton's serialised story
of the rally quattro's which has been in the last 12 or so "audi driver"
magazines.  he dealt with the various iterations of the s1 cars in the last
3 issues, including a nice spec sheet of the rohrl pikes peak car.

interestingly he is promising a (long-awaited) update on his seminal 1984
book on the quattros ("audi quattro, the development & competition
history")...

in the rac rally in 1985, audi did use the pdk (actually "porsche doppel
kupplung")for walter rohrl - but this was his first experience with the pdk
transmission, and he had done no pre-event work (he hated the rally).  the
car (chassis #2) was a handful due in part to the absence of a shake-down
and the weight of the 5-speed transmission unbalancing the car.  after a
while rohrl got used to the car, and began to like the transmission before
he hooked a ditch, hit a rock and flipped, rolling the car down a hill.
there were only two other pdk-equipped s1's, one of those was chassis 15 - a
prototype for testing the transmission.

the pdk was originally developed by porsche for the 962 racecar.

the pdk transmission is, like the dsg vwag one, a dual clutch, dual
mainshaft transmission with each clutch specific to a mainshaft.  unlike
other automated manual transmissions (ferrari, bmw) the dsg does not simply
automate the existing manual change, but allows the pre-selection of 2 gears
simultaneously with the correct gear chosen by the electronics, and the
appropriate clutch engaged.  the other, while still selected, is unengaged
because its clutch is unengaged. this allows very fast changes because 1st,
3rd & 5th are on one shaft, and 2nd, 4th and 6th the other.  as normal
engagement is sequential up and down, you can see how the twin arrangement
would be advantageous, although the electronics can work through a 2-gear
step down if required, although this takes longer (although still well under
a second).  the other main advantage, apart from speed, is smoothness
because, as with the clutch engagement of the latest autos, the transmission
can communicate with the motronic and dip torque during the period of
disengagement/engagement of the 2 gears.  this is not possible in the
bmw/ferrari gearboxes as they have only 1 clutch - which accounts for their
abruptness and roughness when stressed.

the limiting factor with the vwag design is that it is designed for
transverse installation, rather than longitudinal.  whether a longitudinal
version is in the works is unknown.  audi has a surfeit of good transmission
designs now, but the inability of a torque converter to handle high rpms
would seem to favour it's chances on the upcoming hi-po n/a motors...

porsche basically haven't known what to do with the pdk transmission.  in
their thinking, it is not a manual, and it is not an automatic, and they
haven't seen room for it in the 911 - although they are thinking of
introducing one for the 997.

hth,
dave
'01 s8

-----Original Message-----
From: "Louis-Alain RICHARD" <laraa at sympatico.ca>
Date: Sun, 8 Jun 2003 15:19:14 -0400

Scott and Jim,

The car I am referring to is the #4 Quattro S1 at RAC 1985 that can be seen
at footage 1:16:11 of the previously mentioned video. Maybe you don=92t have
the video but, is it possible? Is the #4 car mentioned in your
documentation?
It really sounds like an actual F1, meaning by that sequential, lightning
fast gear changes.
All the others S1 heard in this video sounds like normal period rally cars,
that is fast but deliberate gear changes.

Louis-Alain

PS: can you explain the meanings of PDK and SMS, for us mere mortals? :-))