[ACE-OF-ACES]

Actually, the stock sim climb rate is not as good as this for the late war P-47s,so i have to wonder what map you tested this on.

No need to wonder

Just need to read

Section 2.1 FLIGHT SIMULATION where it states the MAP used is the 'Flight Test Map (BBury)'

The 'Flight Test Map (BBury)' is a map that is set to STD ATM conditions, which is the conditions that all real world flight test data is converted to unless otherwise stated on/in the test data

Winter maps tend to be much more optimistic for some reason.

Colder is better, which is why they allways convert the test reslts to std atm conditions

In any event, it is interesting to know that the sustained climb performance of the late war plane was actually pretty decent. I do think it would be tough to substantiate a 4000+ fpm climb, however, there is a test out there that validates a 5000 fpm climb for a short interval utilizing a zoom from 1500ft.
http://www.wwiiaircraftperformance.org/ ... n-zoom.pdf
It was done to compare zoom climb rates of the late D and N model.
There are two tests, one that zooms from 220IAS into a climb from 1500ft, and another that they start from 220 and zoom to 320 in level flight and then climb.
They timed the climbs at 5000, 8000, and 10,000ft.

ZOOM testing is a whole other type of testing

It is not part of the standard test methods where a constant climb speed is maintained during the climb

The difficult thing about making such comparisons in Il2 is that indicated air speeds are universal in game, where in reality they are all not exactly the same.

The real difficulty is trying to find ZOOM testing that is detailed enough to reproduce the test in the game, that and only a few planes were ever ZOOM tested.