Jetta DSG Transmission
Volkswagen’s Direct Shift Gearbox (DSG) is the world’s first dual-clutch
automated manual gearbox in a production car. This provides the driver the
ease-of-drive of a car equipped with an automatic transmission, but the
efficiency and flexibility of a manual transmission.
It’s like a far more advanced big brother of automated manual transmissions like
the one found in the Proton Savvy AMT. Something like BMW’s SMG, but
Volkswagen’s DSG was the first to have dual clutches. Volkswagen’s DSG
transmission also has a triptronic function, allowing gears to be manually
selected as well as an automatic mode.
A conventional manual gearbox has a human foot-operated single clutch. A DSG
transmission has two clutches, one for the even gears and one for the odd gears
plus the reverse gear. One clutch is in gear, while the other pre-selects the
next gear. This allows really fast shifts, no more than three to four hundredths
of a second. For example, if the car is in third gear, the other clutch already
has fourth gear selected but is not active. As soon as the RPM reaches the ideal
shift point for the car’s torque curve, the gearbox shifts into fourth gear
Volkswagen and Audi's Direct Shift Gearbox (DSG)
From Aaron Gold,
What it is and how it works
The Direct Shift Gearbox (DSG), also known as the double-clutch gearbox, is a
transmission developed by Audi and Volkswagen. What makes it special is that it
can change gears faster than any other geared transmission. The DSG can be
shifted either manually or automatically. It delivers more power and better
control than a traditional automatic transmission and faster performance than a
The DSG is a development of the sequential manual transmission (SMT), which is
essentially a fully-automated manual transmission with a computer-controlled
clutch. Before we delve into the workings of the DSG, let's start with an
explanation of the SMT.
SMT: The control of a manual with the ease of an automatic
Though it has appeared on a few passenger cars, the SMT is widely used in
certain forms of racing and is featured on Ferrari's Enzo supercar.
Cars with SMTs have no clutch pedal; the clutch is automatically engaged. Most
SMTs can be shifted automatically or manually, the latter using a shift lever or
paddles on the steering wheel. The advantage to an SMT is that it uses a solid
coupling, as opposed to a fluid coupling (torque converter) as used in a
traditional automatic (including Tiptronic- or manumatic-style transmissions).
As with a manual transmission, the SMT provides a direct connection between
engine and transmission, allowing 100 of the engine's power to be transmitted to
the wheels. The SMT provides more immediate response and ensures that the engine
RPMs do not drop when the driver lifts off the accelerator (as happens with an
automatic), giving her more precise control over power output.
SMTs can also perform matched-rev (or double-clutch) downshifts: When the driver
downshifts, the SMT disengages the clutch, shifts to neutral, and re-engages the
clutch. The SMT calculates what the engine RPMs will be in the next-lowest gear
based on the current road speed, and revs the engine (and, since the clutch is
engaged, the transmission) to that speed. It then disengages the clutch, shifts
into the lower gear, and re-engages the clutch. The result is a smooth change
with no jerk and no sudden deceleration.
SMTs have one major disadvantage, same as a manual: Power must be interrupted
while the transmission changes gears.
DSG: An SMT without the lag
The DSG all but eliminates the lag inherent in SMTs. The DSG is essentially two
3-speed gearboxes with a pair of clutches. When the driver starts out,
transmission #1 is in first gear and transmission #2 is in second. The clutch
engages and the car starts out in first. When it's time to change gears, the DSG
uses the clutches to swap transmissions. The #1 transmission immediately shifts
to third gear. At the next change the DSG swaps transmissions again, and #2
shifts to fourth. The DSG's computerized controller calculates the next likely
gearchange and shifts the "idle" transmission into that gear. The advantage is
the speed of gearchanges: The DSG takes about 8 milliseconds to upshift. Compare
that to the SMT in the Ferrari Enzo, which takes 150 ms to upshift. It's also
significantly faster than a human: According to Audi, the A3 runs 0-60 in 6.9
seconds with a 6-speed manual and 6.7 seconds with the 6-speed DSG. Like the SMT,
the DSG performs double-clutch downshifts and can skip gears (i.e. downshifting
from 6th directly to 4th, 3rd, etc).
Driving with the DSG
The DSG uses a traditional P-R-N-D-S shift pattern. It can shift automatically
in either normal (D) or Sport (S) modes. In Normal mode, the DSG shifts to the
higher gears early in order to minimize engine noise and maximize fuel economy.
In Sport mode the transmission holds the lower gears longer in order to keep the
engine in its powerband. This is especially useful for turbocharged cars like
Audi A3, Volkswagen GTI and VW Jetta GLI, since the turbocharger is only active
at higher RPMs. Sport mode also provides more aggressive downshifts with slight
accelerator pedal pressure.
Manual mode is engaged by either sliding the shift lever to the side or pulling
one of the paddles on the steering wheel. Once in manual mode, shifts are made
by moving the shifter fore and aft or using the paddles (which are marked " "
and "-"). If manual mode was engaged with the paddles, pulling and holding the
upshift paddle returns the transmission to automatic mode, allowing the driver
to quickly downshift to a lower gear for passing and then hand control back over
to the transmission.
Good Video of DSG Design (Click the Play button twice)