The torque value to the rolls when accelerating will be a bit lower than the full brake torque if the vehicle is held at a discrete rpm by the dyno. I don't think the difference is significant..........but, if you're measuring brake torque and not deriving torque from acceleration..........it's the proper way to make the test.

I'm sure they could do it in this fashion, but the engine would be at maximum power for at least one minute..........could be problematical.

I ran some calculations and had another think about that dyno.

The machine doesn't need any gear ratios or final drive ratios for the calculations. It only needs to know torque at the wheels, wheel speed, and engine speed and it can provide a proper printout.

So, the only remaining question is how they accurately measure engine speed on a diesel?

Reflective strip on the crank damper and optical pickup.

Perfect.

The printouts will be accurate.........although the operator doesn't have a clue why that will be so.

Sadly, that's the case with most services of most varieties, at least in the U.S. People seem to be content to just do what the various manuals say and never ask "why?".

Its been nice to learn a little more about how a dyno works:D

http://i3.photobucket.com/albums/y71...yno_pull_2.jpg

Oh wait, you wanted Mercedes dyno sheets... :D