Derived as a modest development of the Twin Wasp R-1830, the R-2000 was designed specifically for the Douglas DC-4 commercial airliner, allowing use of lower octane fuel than generally used by the military. It was also used on the Air Force C-54 and Navy R5D (military versions of the DC-4); the Vought XF5U-1; Chase YC-122; and Cancargo CBY-3.
This engine, known as the X-100 (Pratt & Whitney's 100th experimental engine), was completed in 1940 as an R-2000 DG. During seven years of experimental development, it was changed into nearly every subtype of R-2000 engine to test many design improvements. In November 1945, it was converted to a post-World War II commercial 2SD13-G engine. After 4,493 hours of experimental operation, the X 100's last run was in October 1947. It was later restored to the 2SD13-G configuration for the Museum.