Thanks to Kurfürst there is finally some written evidence of the old days.
I just want to add an article from Flugzeug Classic from 12/2004, that was passed on from a friend to me.
This article is talking about increasing the power of the FW-190s BMW 801 D engine.
In the article the MW50 testing is explained in detail.
First tests showed:
-Temperature increase was only 7°C
-The charge air intake temperature was reduced by 45°C
-No engine disturbance where witnessed
-Speed increase of 16km/h at 100m
NOT VERY IMPESSSIVE ON THE FOCKE BUT EXPLAINS AND DOCUMENTS THE DECREASE OF ENGINE TEMPERATURE WHEN USING MW-50.
Later performance was increased by injecting C3 named Erhöhte Notleisting (documented since 1943):
-Increasing the manifold pressure
-additional Injection of C3
-below 1000m
-duration 10-15 minutes
-only at Full Throttle at automatic PropPitch
-Speed-Increase was 22km/h at low level and 25km/h at higher altitudes
THIS IS ONLY REFLECTING TEST ON FW-190 SERIES!!!!
The article apparently refers in the very end that very much later MW-50 and C3 injection was used in the later D9 series.