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Air Force Museum Foundation

Wright R-2600-13


(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.

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