I have recollections of a pre-war 250cc DKW winning a major endurance race in South Africa, blitzed the opposition but was disqualified due to excessive noise.
This site shows the principle of the “twin cylinder” engine it used, plus of course the deflector piston in the early engines. https://www.odd-bike.com/2014/02/dkw-supercharged-two-strokes-force-fed.html
