Motorenfabrik Oberursel A.G. was a German manufacturer of automobile, locomotive and aircraft engines situated in Oberursel (Taunus), near Frankfurt (Main), Germany. During World War I it supplied a major 100 hp-class rotary engine that was used in a number of early-war fighter aircraft designs. In 1921 the company merged with Deutz AG, and then again in 1930 with Humboldt-Deutz Motoren, and finally in 1938 with Klöcknerwerke AG. From this point on they were known as the Klöckner-Humboldt-Deutz Oberursel factory, known primarily for their locomotive engines. Today they are part of Rolls-Royce Deutschland, and produce one family of their jet engines.
The factory in Oberursel is claimed to be the oldest surviving aircraft engine factory in the world.
Early years
The company had its origins in 1891, when Willy Seck invented a new gasoline fuel injection system and produced a small one-cylinder stationary engine of about 4 hp, which he called the Gnom.
The following year he founded Willy Seck & Co. to sell the design, which became famous around the world.::
;Oberursel U.III: Gnome Double Lambda 14-cylinder, two-row rotary engine copy, 160 hp (120 kW) and total displacement to with stroke.
;Oberursel Ur.II: Clone of the Le Rhone 9J 110 hp (82 kW) nine cylinder rotary.
;Oberursel Ur.III: 11-cylinder development of the Ur.II. 145 hp (108 kW) and total displacement to
;Oberursel 200 hp 18-cyl rotary: