I did a few tests, nothing exceptional but gives you a good idea of the difference between the variants:
20,000ft
TEST - Aircraft slowed to 150mph and held there for several seconds. Then throttle increased to desired level and time to accelerate noted.
25% fuel NON-WEP
150 175 200 225 250 275 300 (indicated airspeed)
F4U-1 N/A 013 033 056 090 150 N/A -- MAX 290mph (7min)
F4U-1D N/A 012 029 050 085 150 N/A -- MAX 285mph (7min)
F4U-4 N/A 009 023 038 062 097 215 -- MAX 305mph (7min)
WEP
F4U-4 N/A 008 020 034 052 076 128 -- MAX 320mph (5min)
F4U-1 is nothing if not beautiful :)
[ 10-06-2001: Message edited by: -duma- ]