Porsche 911 - Manual (Page 26)

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911 Carrera Cabriolet
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The new 911 | Transmission
The optional Porsche Doppelkup-
plung (PDK), with both manual
gearshift and an automatic mode,
enables smooth gear changes
with no interruption in the flow of
power. This results in significantly
faster acceleration and lower
fuel consumption, without having
to sacrifice the ease of automatic
transmission.
In total, PDK has seven gears at
its disposal. Gears 1 to 6 have
a sports ratio and top speed is
reached in 6 th gear. The 7 th gear
has a long ratio and reduces fuel
consumption even further.
PDK is like having two gearboxes
in one and thus requires two
clutches – designed as a double
wet clutch transmission.
This double clutch provides
an alternating, non-positive
connection between the gearbox
and the engine by means of
two separate input shafts (input
shaft 1 is nested inside the
hollowed-out input shaft 2).
The flow of power from the engine
is only ever transmitted through
one clutch at a time, while the
next gear is preselected by the
second clutch. During a gear
change, a conventional shift no
longer takes place. Instead,
one clutch simply opens and the
other closes at the same time.
Gear changes therefore take
place within a few hundredths of
a second.
Clutch 1 controls the odd gears
(1, 3, 5, 7) and reverse. Clutch 2
controls the even gears (2, 4, 6).
As if one clutch didn’t deliver enough performance already.
Porsche Doppelkupplung (PDK).