Questions about the Ki-83 and Japanese aircraft metrics

I remember reading somewhere that the Japanese didn't list their top speeds based on war emergency power but instead military power. This means a simple calculation would be made to extrapolate from MP to WEP top speed if WEP top speed was not listed. Supposedly the Ki-83 top speed that is commonly listed is based on the MP rating rather than the WEP rating. The secondary one is a top speed that the US managed with high octane fuel. However, this was done during a USAF conducted test. The common metrics would be based on WEP for that test. With this in mind, the top speed was recorded at 762 km/h. So this is to say that the Ki-83 should have a higher top speed on WEP than is listed everywhere else.

Ottobon said:

Nothing much to add, especially as i don't directly have a link to the discussion, but a buddy of mine who used to frequent J-Aircraft and normally is a great knowledge base on Japanese aircraft once mentioned that they had a large discussion about the Ki-83s top speed and to the best of their abilities concluded that it was most likely in the range of 730kph with WEP (notable because the Japanese never tested speed or climb at anything beyond Military), and that the various figures putting it at about 760kph probably would of required quite a bit of extra horsepower (400hp i believe.)

However this is literally a retelling of a discussion about a discussion from a trustworthy friend ("Hiromachi"), so of course understand i am not claiming concrete knowledge on the matter. (if anybody can find this discussion on J-aircraft please link it, so far I've come up with nothing)

I would add that i would love to know more about its wing design, but finding much of anything concrete about this aircraft seems rather hard. Without a doubt though it was a good design and surprisingly attractive.

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Ki-83, was it as good as thought?

If anyone has flight data that would be great. I want to verify that the top speed could actually be 730 km/h on WEP if the top speed is 704 on MP and that the Japanese used MP to define the primary parameters of their aircraft. If any sources can be provided that denote anything regarding their testing processes in WWII Japan that would be much appreciated.