Junkers Jumo 210
Development of the V12 Jumo 210 itself started in 1931 under the designation L10. The L10 was Germany's first truly modern engine design, featuring three valves per cylinder, an inverted-V layout, a supercharger as standard equipment, and a cast cylinder block. The 210 was odd in that the cylinders were machined into a block along with one side of the crankcase, two such parts being bolted together side-by-side to form the engine. Normal construction techniques used three parts, two cylinder blocks and a separate crankcase.
The L10 was first ran in static tests on October 22, 1932. With the official formation of the RLM in 1933, engine naming was rationalized with Junkers receiving the "200 block", the L10 becoming the 210. Type approval was achieved in March 1934, and it first flew on July 5, 1934 installed in a Junkers W33. The design had initially aimed for 700 PS, but the prototypes delivered only about 600 PS, so there was some disappointment in the industry. Nevertheless almost all German aircraft designs of the era were based on the 210, which is why they were so small compared to other country's efforts.
Initial production of the 610 PS (602 hp, 449 kW) Jumo 210A started in late 1934. Further development led in 1935 to the 640 PS (631 hp, 471 kW) 210B and 210C. Both added a new supercharger for improved performance, along with a dump valve to avoid overboost. The B model had its propeller geared at 1:1.55 (prop:engine rpm) for high-speed use, while the C model was geared at 1:1.63 for slower flying speeds. In 1936 the new 670 PS (661 hp, 493 kW) 210D and 210E were introduced, which had the same gearing as the B/C but used a new two-speed supercharger to increase takeoff power and altitude performance.
The Jumo 210G had a direct injection system developed by Dr. Lichte. The Jumo system used a small pump piston positioned beside each of the main cylinders, driven off the crank shaft. The injector used a simple check valve to prevent internal pressure from blowing back into the fuel line, and the pump was timed to inject at the proper point in the intake cycle. Inclusion of the injection system increased takeoff performance by about 20 PS without increasing boost rates and it also reduced fuel consumption. For those reasons most newer German engine types were set up with fuel injection systems. The Jumo 210G was rated at 700 PS (690 hp, 515 kW) and was only available for fast aircraft like the Bf 109 or Bf 110 but not for slow aircraft like the Ju 87.
Further developments were planned as Jumo 210F and 210H, but never built. In 1935 the Jumo 210H was used for development of the Jumo 211. A Jumo 210S was a special development by the DVL with special regulation mechanisms. Production of the Jumo 210 came to an end in about 1938.