The max speed setting in the motorized car was factory set to the maximum speed.
My software calibration measured the following scale speeds
speed step forwards backwards
1 19km/h 18km/h
5+ 138km/h 158km/h
10 318km/h 208km/h
I decided that it was way too fast for my layout and decided to reduce the speed by reducing the max speed pot by a 180° turn. (My longest straight track that is visible is only 2,5m long)
This shows the calibrated speeds of my ICE 3 train after reducing the max speed setting with a 180° turn of the speed pot.
It seems that the intermediate speed steps are not all that significant - and are often the same as the non intermediate speed.
All speeds measured with acceleration off.
As you can see the speeds increase pretty much linearly with the speed step.