Junkers Jumo 205

Junkers Jumo 205, a photo by fangleman on Flickr.

From the Wiki:
"The Junkers Jumo 205 aircraft engine was the most famous of a series of Diesel engines that were the first, and for more than half a century the only, successful aircraft Diesel engines. The Jumo 204 first entered service in 1932. Later engines in the series were styled Jumo 206, Jumo 207 and Jumo 208, and differed in stroke and bore and supercharging arrangements. In all more than 900 of these engines were produced."
en.wikipedia.org/wiki/Junkers_Jumo_205