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Junkers Jumo 211

[Source: Bundesarchiv, Bild 101I-378-0037-16A / Böcker / CC-BY-SA]

(Specifications for Jumo 211F)
Manufacturer: Junkers
Type: Supercharged liquid-cooled inverted Vee piston engine
Cylinder: 12
Bore: 150 mm (5.9 in)
Stroke: 165 mm (6.5 in)
Displacement: 34,99 L
Dry weight: 720 kg
Power output: 1,340 hp at 2600 rpm
Compression ratio: 6,5:1
Specific fuel consumption: 0,54 kg/hp

Comments - Source: Wikipedia
The Jumo 211 was an inverted V-12 aircraft engine, Junkers Motoren's primary aircraft engine of World War II. It was the direct competitor to the famous Daimler-Benz DB 601 and closely paralleled its development. While the Daimler-Benz engine was mostly used in fighters and destroyers, the Jumo engine was primarily used in bombers such as Junker's own Ju 88 and Ju 87.

The Jumo 211 was developed by Dr. Neugebauer as scaled-up successor to the earlier Jumo 210. In 1934, even before the new Jumo 210 had completed its acceptance tests, the RLM sent out a request for a new 1,000 hp-class engine of about 500 kg weight. Both Jumo and Daimler-Benz responded, and in order to reach service before the new Daimler-Benz DB 600, the Jumo team decided to make their new design as similar as possible to their 210H model, currently in testing.

The resulting Jumo 211 was first prototyped at Jumo's Dessau plant in 1935 and started testing in April 1936. Limited production of the 1,100 hp Jumo 211A started in April 1937 at Dessau, with just over 1,000 completed before full production was started at Magdeburg in July. Three models were provided with varied settings for its two-speed supercharger, tuned for different low- vs. high-altitude performance. The first aircraft powered by the 211A arrived that November.

But by this time the 600 had finally arrived. Unlike the 211, the 600 was an all-new design that introduced a number of new features. Notably it used a pressurized water cooling system that allowed it to use much less water inside the engine, and resulted in a smaller and lighter engine and radiator. Additionally the higher pressures allowed the water to remain a liquid at all altitudes, allowing it to keep the engine cool at higher power settings. The unpressurized 211's water would boil as the aircraft climbed, reducing cooling capability and limiting it to lower power settings. Combined with a more powerful supercharger, the 600 was able to outperform the 211 at medium and high altitudes, relegating the 211 to lower altitude roles. Although many designs had already used the 211, including fighters like the Bf 109 and Me 110, these quickly moved to the 600 (and later the DB 601). The 211 then became the major bomber engine of the war, in no small part due to Junkers also building mo st of the bombers then in use.

Development of the 211 continued with the Jumo 211B being released in 1938, with a slightly increased maximum RPM of 2,400 which boosted power to 1,200 hp. The 211C and 211D differed primarily in the propeller gear ratios and other features.

A major upgrade was started in 1940 in order to better compete with the 601, following in its footsteps with a pressurized cooling system. The resulting 211E proved to be able to run at much higher power settings without overheating, so it was quickly followed by the 211F which included a strengthened crankshaft and a more efficient supercharger. Running at 2,600 RPM the F and similar J engines delivered a much improved 1,350 hp. Further improvements to this basic line led to the 1,425 hp 211N and 1,475 hp 211P. Continued development of the 211 line ended in favor of the re-named Junkers Jumo 213.

Total production of the 211 series amounted to 68,248 engines with a production peak of 1700 engines per month in the autumn of 1942.