From the F87 technical training guide posted here on Bimmerpost:
"The exhaust sound of the F87 BMW M2 is much more powerful and emotional than in the F2x standard vehicles. The exhaust flap is closed when the engine is idling with the vehicle stationary, in the lower engine speed range in all speed ranges and when the driving experience switch is in COMFORT position.
In the upper engine speed ranges, the flap opens depending on the load.
When the driving experience switch is in SPORT and SPORT+ positions, the exhaust flap is fully open when the engine is idling while the vehicle is stationary and in the lower gears.
In the higher gears, the exhaust flap is closed in the critical ranges. The same applies in the upper engine speed ranges depending on the load."
http://f87.bimmerpost.com/forums/att...2&d=1454979963