Radial Engine of the Day

Wright R-3350 Duplex-Cyclone
Type: Twin-row 18-cylinder, supercharged, air-cooled radial engine
Bore: 6.125 inches (155.6 mm)
Stroke: 6.312 ininches (160.2 mm)
Dry weight: 2,670 pounds (1,210 kg)
Displacement: 3,347 cubic inches (54.86 L)
Power output: 2,200 to over 3,700 hp (various models)

http://www.youtube.com/watch?v=2d4HQ8ZM_2k

Used on the Boeing B-29 Superfortress.