Wright R-2600-13 By (Excerpted from North American Aviation Field Service Manual for B-25C and D) The Wright Cyclone, Model C14B, carries the Army Air Forces designation R-2600-13. The "R" stands for radial type of engine, "2600" stands for the number of cubic inches piston displacement, and the "13" is the model number. The engines are air-cooled, static, staggered, twin-row radial type having two speed superchargers. Owing to the high compression ratio of 6.9:1, the engine operates on 100-Octane fuel. No other fuel may be used except in the event of an emergency, when a fuel of the next highest Octane rating may be used. Under normal operating conditions, the engines develop a maximum of 1700 bhp (brake horsepower) for take-off at 44.3" Hg. (manifold pressure -- in inches of mercury -- of the fuel-air mixture in the engine intake pipes after passing through the supercharger) and 2600 rpm (revolutions per minute of the crankshaft, not the propeller). The cylinders are numbered in a clockwise direction when looking from the rear, or anti-propeller end, forward to the propeller end. No. 1 cylinder is the top cylinder of the rear row. No. 2 is to its right in the front row. Thus, all odd numbered cylinders are in the rear row and all even numbered cylinders in the front row. TECHNICAL NOTES: Model: R-2600-13 (Wright Cyclone Model C14B) Type: Static Radial, Air Cooled, Double Row Number of cylinders: 14 Bore: 6.125 in. Stroke: 6.312 in. Piston displacement: 2603 cu.in. Compression ratio: 6.90:1 Blower gear ratio: 7.06:1 and 10.06:1 Blower diameter: 11.00 in. Rated rpm of crankshaft: 2400 Rated bph/rpm at 6700 ft.: 1500/2400 Rated bhp/rpm at 13,000 ft.: 1350/2400 Takeoff bhp/rpm: 1700/2600 Rotation of crankshaft (from anti-propeller end): Clockwise Rotation of propeller (from anti-propeller end): Clockwise Propeller reduction gear ration (crankshaft to propeller): 16:9 Average weight of engine: 1978.50 lbs. Overall length of engine: 63.10 in. Overall diameter of engine: 54.26 in. Click here to return to the World War II Gallery.