I'm basing this on the 6-speed DSG transmission in my Mk6 GTI DSG. (As far as I am aware only the 6 Speed DSG gearboxes have Launch Control, the 7 speed versions don't
)
But, to use Launch Control:
NB: In my experience the car prevents you using launch control if the car is not warmed up properly, so make sure you've warmed up the car.
1. Bring the vehicle to a complete stop with the engine running.
2. Hold the vehicle stationary with light pressure on the brake pedal.
3. Select either "S" or "+/-" modes with the gear selector.
4. Turn off the Traction Control (usually need to hold the TCS button for a second or two)
5. Press firmly on the brake pedal.
6. Fully depress the throttle. (The revs will be limited to 4000rpm if the car is standard. Some tuners can raise the launch rpms with software.)
7. When ready, release the brake pedal and the car will launch.
With the AWD you shouldn't have any worries about traction. Because it's an issue for the FWD cars, you'll find posts online suggesting to launch about 2500-2750rpm. In the R, you should be fine launching it at the maximum rpm available (ie. 4000rpm in a standard car).
