Hi, guys
Here in this thread is a lot of good advice so far.
I would say that all engines have a maximum sustainable revolutions per minute. The maximum sustainable RPM varies with each engine type.
Speaking only in general terms:
1) In-line, V, and opposing cylinder designs typically ( but not always ) have a maximum sustainable RPM of about 2,400 to 3,000 RPMs - depending on individual engine type. A particular V engine might have a maximum of about 2,700 sustainable RPM, for example.
2) Radial engines are generally less in maximum sustainable RPM ( compared to the V-block engines ) by a couple hundred or more. Typical would be about 2,300 to 2,800 maximum sustainable RPM. This does not hinder the power results of them, however, because of the high torque of radial engines.
There are a few engines which are exceptions to these ranges.
For World War Two fighters, especially front line types like the Bf-109s, it is ideal to keep the RPM at maximum sustainable RPM from take-off until circling the base to land. ( Sometimes pilots under attack while landing would do a "hot landing" at high speed if there was a long enough runway, but that is another exception. )
Keeping the RPM at maximum sustainable RPM is the only sure way of ensuring the most power for long periods, keeping in mind that your throttle position will change somewhat in diving and climbing despite this. For this reason we should be looking at the RPM gauge to judge what throttle changes to make.
For aircraft with automatic pitch prop adjustment, this is much easier. ( For other planes, you will have to adjust prop pitch. )
Find the maximum sustainable RPM for your aircraft type and fly according to it during take-off and combat.
For the Bf-109 types, this is easier than some other fighters because of automatic systems. It shows how important it is to
know your planes capabilities.
This will give you the most power without damaging your engine.
In conclusion: The rated Maximum Sustainable RPM is the most important issue, but radiator flaps and Methol Water Injection are factors, too.
The stock IL-2 1946 has a tutorial mission on how to fly the Bf-109, which might help.
Fireskull