In 1943, two P-47D-15-RE airframes were selected for testing with the new experimental 2300 hp Chrysler XIV-2220-1 sixteen-cylinder inverted Vee liquid-cooled engine.
These aircraft were redesignated XP-47H.
The liquid-cooled Chrysler engine with its large under-fuselage radiator radically changed the appearance of the Thunderbolt and increased overall length to 39 feet 2 inches.
With the increased power and improved streamlining, a maximum speed of 490 mph was anticipated.
Although the project had begun in August 1943, the two P-47D-15-RE airframes were not actually converted until 1945.
Test flights began on July 26, 1945.
One of the XP-47Hs actually attained a speed of 490 mph in level flight during flight trials.
The Chrysler XIV-2220 engine never achieved production and the advent of jet propulsion killed any further USAAF interest in the development of even faster piston-engine fighters.
Consequently, no further work was undertaken on the XP-47H project.