Kurt Tank successfully fitted a BMW 801 to a new fighter design he was working on, and as a result the 801 became best known as the power plant for the famous Focke-Wulf Fw 190.

Radial engines were rare in European designs as they were considered to have too large a frontal area for good streamlining and would not be suitable for high speed aircraft.

The main concern was providing cooling air over the cylinder heads, which generally required a very large opening at the front of the aircraft.

Tank's solution for the BMW 139 was to use an engine-driven fan behind an oversized, flow-through hollow prop-spinner open at the extreme front, blowing air past the engine cylinders, with some of it being drawn through S-shaped ducts over a radiator for oil cooling.

However this system proved almost impossible to operate properly with the BMW 139; early prototypes of the Fw 190 demonstrated terrible cooling problems.

Several minor advances were worked into the design, including the use of sodium-cooled valves and a direct fuel injection system, manufactured by Friedrich Deckel AG of Munich.

The supercharger was rather basic in the early models, using a single-stage two-speed design directly geared to the engine (unlike the DB 601's hydraulically clutched version) which led to rather limited altitude performance, in keeping with its intended medium-altitude usage.

The BMW 801G-2 and H-2 models were D-2 engines modified for use in bomber roles with lower gear ratios for driving larger propellers, clockwise and counterclockwise respectively.

[6] [7] The D-2 models were tested with a system for injecting a 50–50 water-methanol mixture known as MW50 into the supercharger primarily for its anti-detonation effect, allowing the use of increased boost pressures.

The E model was also used as the basis for the BMW 801R, which included a much more complex and powerful two-stage four-speed supercharger, as well as die cast hydronalium cylinder heads, strengthened crankshaft and pistons, and chromed cylinders and exhaust valves; it was anticipated this version would produce over 2,000 hp (1,500 kW; 2,000 PS), or over 2,600 hp (1,900 kW; 2,600 PS) with MW 50 methanol-water injection.

As just one result of the highest level of priority given to the successful 801 design's further development, a number of attempts were made to use turbochargers on the BMW 801 series as well.

A sizable number of BMW 801s exist in museums, some on display by themselves, with some 20 of them associated with surviving examples of the Focke-Wulf Fw 190s that they powered in World War II.

[15] The sole surviving Ju 388, in the hands of the Udvar-Hazy Center of the Smithsonian, has a pair of complete BMW 801J turbocharged engines still in its nacelles.

There is an 801-ML (801L) on display mounted in a Dornier 217 nacelle, essentially a complete surviving Motoranlage unitized powerplant, at the New England Air Museum, Bradley International Airport, Windsor Locks, CT.[16] Likewise, the Ju 88R-1 night fighter at the Royal Air Force Museum London (see photo above) also has unitized BMW 801 radials installed.

The cylinders had both bore and stroke of 156 millimetres (6.1 in), giving a total capacity of 41.8 litres (2,550 cu in), just a bit less than the American Wright Cyclone 14 twin-row radial of some 1,600 to 1,900 hp output.

This provided effective cooling although at the cost of about 70 PS (69 hp, 51.5 kW) required to drive the fan when the aircraft was at low speed.

Above 170 miles per hour (270 km/h), the fan absorbed little power directly as the vacuum effect of the airflow past the air exits provided the needed flow.

The outer portion of the oil cooler's core was in contact with the main cowling's sheetmetal, to possibly act as a heat sink.

Airflow past the gap between the cowl and outer lip of the metal ring produced a vacuum effect that pulled air from the front of the engine outward and forward within the cowl's frontmost inner area just behind the fan, flowing forward across the oil cooler core in a separate airflow path from the rearwards-direction flow that cooled the engine's cylinders, just to provide cooling for the 801's oil.

The rate of cooling airflow over the core could be controlled by moving the metal ring slightly forward or aft in order to open or close the gap.

The downside to this design was that the oil cooler was in an extremely vulnerable location, and the metal ring was increasingly armoured as the war progressed.

Engines were typically delivered from BMW complete in their cowling, ready to be bolted to the front of the aircraft or nacelle, since 1942 as Motoranlage (M) and 1944/1945 as Triebwerksanlage (T).

The Motoranlage was the original form of the interchangeable Kraftei, or "power-egg", unitized powerplant installation concept used in many German wartime aircraft.

Both M and T formats were also used with various inline engines, like the Daimler-Benz DB 603 used for both the inline-engined versions of the Do 217 and the enormous BV 238 flying boat, and the Junkers Jumo 213 powerplants used for later marks of the Ju 88 multirole aircraft.