Radiator/cowling flaps

[horseback]

I race motorcycles so I am aware of the significant increase in wear and fatigue from even slight increases in power settings.

Then you must have used a few tricks to get more power from the engine, possibly replacing the stock throttle system with one that lets you use more of the engine's potential power. Most cars and bikes rated for street use do not use the full throttle capacity of their engines, because the engineers know that the engine will wear out sooner (and the normal user will never need to accelerate at the full throttle rate, much less travel at the speeds it would allow) and use much more fuel. And of course there's that liability thing here in the States.

Of course, we have a much better understanding of metallurgy, coolants and lubricants today than we did in 1939-45.

Similarly, the high performance engines that powered WWII aircraft were limited by the engineers in various ways; how much they were limited depended upon the quality of the fuel and lubricants, the expected atmospheric conditions, including the quality of the cooling systems (as I recall, most early war Soviet fighters lacked glycol cooling, which severely limited both the power of their inline engines and their time between overhaul).

All of this is the long way of saying that the limits on WEP use were very specific to a given engine and aircraft, and in some cases changed with better manufacturing techniques as the wartime workforce learned on the job. Consult your real life aircraft's manual for general guidance, and experiment a little on your own to see if the Il-2 '46 FM matches it (many aircraft do).

cheers

horseback