While very specific fine-tuning of rotaries in not possible in the sim world (there was an attempt years ago for RB3D by GabiLaser, a nice little program called "ReLoad") - some realistic throttle settings that work well are:
- early rotaries such as on the Bristol Scout, Fok E.I/II/III at 100% power or off (use mixture adjustment and blip for limited control)
- Gnome rotaries on the Camel (for the Bentley variant if you want to use it as a Gnome-powered one), either at about 80% or 100% power (use mixture adjustment and blip for limited control); this also applies to Gnome engines on the DH.2
- all other rotaries, use something like 40, 60, 80 and 100% power, again with mixture adjustment and blip for further control
- for 3 / 6 / 9 cylinder power on Gnome rotaries for example, use again the 40/60/80/100% power brackets suggested above if you like, for realism
- keep in mind that most rotaries would cut out below about 50% power (I'm being optimistic with the 40% cutoff point for a "very nicely" tuned engine)
- on my rotaries I usually just toggle quickly between 40/60/80/100% power across all the types, for simplicity, and use blip to control further (without fiddling with mixture adjustment while in flight)
I'm sure some of the engine and carb. experts will pitch in further with more detailed info.