ⓘ Blog | BMW VI - bmw. The BMW VI was a water-cooled V-12 aircraft engine built in Germany in the 1920s. It was one of the most important German aero engines in the y ..



The BMW VI was a water-cooled V-12 aircraft engine built in Germany in the 1920s. It was one of the most important German aero engines in the years leading up to World War II, with thousands built. It was further developed as the BMW VII and BMW IX, although these saw considerably less use. It was also produced in the Soviet Union as the M-17 and Japan as the Kawasaki Ha-9.


1. Design and development

The BMW VI was the first twelve-cylinder engine built by the BMW. It essentially consisted of two cylinder banks from the six-cylinder BMW IV bolted to a common cast aluminium crankcase at a 60-degree included angle between the cylinder banks. Series production commenced in 1926 after type approval had been granted. From 1930 on, after 1000 engines of the BMW VI type had already been delivered, Germany was again permitted to construct military aircraft. The sudden additional demand resulted in the production figures increasing rapidly. In 1933 the BMW VI was used for BMWs first experiments with direct fuel injection.

The BMW VI was the chosen source of power for numerous record-breaking and long-distance flights, including an east-to-west crossing of the Atlantic in 1930 and a round-the world flight in 1932, both by Wolfgang von Gronau in an open Dornier Wal flying boat powered by two BMW VI engines.

The BMW VI was put to unusual use as a power unit for the "Rail Zeppelin" high-speed railcar. Many versions of the BMW VI engine were developed, and it was built under license in Japan and the Soviet Union. This was further evidence of the reliability of an engine with which BMW made a fundamental contribution to the build-up of German air transport. At least 9.200 were built between 1926 and 1938. The engine was license-built in the Soviet Union under the supervision of Mikulin, who then further developed it as the M-17. More license built engines were produced by Kawasaki Heavy Industries in Japan as the Kawasaki Ha9 long designation:- Army Type 98 850hp Liquid Cooled In-line.


2. Variants

5.5, 6 or 7.3 denotes compression ratio. No additional letter denotes BMW carburetor and direct-drive propeller 7.3, u denotes a propeller reduction gear 7.3u, z denotes Zenith carburetor 7.3z, zu denotes Zenith carburetor and propeller reduction gear 7.3zu.

BMW VI 5.5 Compression ratio 5.5:1, 600–650 PS 592–641 hp at up to 1600 rpm at sea level BMW VI 6.0 Compression ratio 6:1, 630–660 PS 621–651 hp at up to 1650 rpm at sea level, 80 Octane fuel BMW VI 7.3 Compression ratio 7.3:1 680–750 PS 671–740 hp at up to 1700 rpm at sea level, 87 Octane fuel Mikulin M-17 Licence production in the USSR Kawasaki Ha9 long designation:- Army Type 98 850hp Liquid Cooled In-line licence production in Japan by Kawasaki

3.1. Specifications BMW VI 7.3z {direct drive} General characteristics

  • Displacement: 46.95 L 2.865.06 cu in
  • Height: 1.103 mm 43.43 in
  • Type: V-12, 60° water-cooled piston engine
  • Stroke: 190 mm 7.48 in / 199 mm 7.83 in different between right and left cylinder bank due to articulated connecting rods.
  • Bore: 160 mm 6.30 in
  • Dry weight: 510 kg 1.124 lb
  • Width: 859 mm 33.82 in
  • Length: 1.810 mm 71.26 in

3.2. Specifications BMW VI 7.3z {direct drive} Components

  • Fuel system: 2 x Zenith 60 DCL
  • Reduction gear: none
  • Valvetrain: 1 inlet + 1 exhaust valve per cylinder operated by a shaft driven overhead camshaft via rockers
  • Cooling system: Liquid-cooled
  • Fuel type: min. 87 octane gasoline

3.3. Specifications BMW VI 7.3z {direct drive} Performance

  • Power output
  • 550 PS 542 hp; 405 kW at 1.530 rpm max. duration at sea level
  • 620 PS 612 hp; 456 kW at 1.590 rpm 30 minutes at sea level
  • 690 PS 681 hp; 507 kW at 1.650 rpm 5 minutes at sea level
  • 750 PS 740 hp; 552 kW for takeoff at 1.700 rpm 1 minute at sea level
  • Specific fuel consumption
  • Specific power: 16 PS/l 0.26 hp/cu in; 11.77 kW/l
  • Compression ratio: 7.3
  • 0.225 kg/PS/h 0.503 lb/hp/h; 0.306 kg/kW/h at 1530 rpm
  • 0.23 kg/PS/h 0.514 lb/hp/h; 0.313 kg/kW/h at 1590 rpm
  • Oil consumption: 0.003–0.01 kg/PS/h 0.007–0.022 lb/hp/h; 0.004–0.014 kg/kW/h at 1.530 rpm
  • B.M.E.P.: 6.9 atm 7.0 bar; 101 psi
  • Power-to-weight ratio: 1.47 PS/kg 0.66 hp/lb; 1.08 kW/kg

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