Hi!
I am not 100% never tried it with vag com, but other tools similar to vag com will do it, and can give you a dyno graph print out of BHP and Torque,
It’s down to time calculation of the cars weight, wheel ratio and final drive ratio combined with acceleration speeds at points against times. lol
Dont ask me how to work it out as I dont know.
I think you can use vag com logging to record speeds and times. Then you find out the mathematical equations so you can work your BHP at the wheels.
It won’t be 100% unless you have the cars frontal area in to account then your still a good % out.
Look at this
http://www.palmerperformance.com/products/pcmscan/download.php But this tool aint too bad, The BHP calc is always around 10% down on what we get on the rolling road.
Nick