Rolls-Royce Exe / Pennine
The first Rolls-Royce engine to be named after a river, as are the modern turbojets, was this experimental unit, which was notable in having sleeve valves and pressure-air cooling. Its 24 cylinders were arranged in X form, in four banks of six, and the capacity was 22 litres. Rated output was 1,200 h.p. at 4,000 ft. The Exe was test flown in a Fairey Battle during 1938, but the project was shelved when it became clear that the company's main productive capacity must be devoted to the Merlin. Another experimental unit related to the Exe was the Pennine, and it may be noted here that in the years preceding the war Rolls-Royce were experimenting with two-stroke as well as four-stroke engines, and continued the compression-ignition experiments started with the Condor. The H layout was also examined.