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During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure.
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Wasnt 100 octane fuel used ONLY by the Americans?
Also, those RPMs are easy to maintain WITHOUT a load, as was stated above. The engine has to work harder to maintian those RPMs when you have a MASSIVE propeller on the front. I dont know any pilot what so ever who doesnt cut RPMs at least slightly, even those who tow ENTIRE GLIDERS cut it back And immidiatly get as much cold air over the engine as possible when they release to cool things down.