The Jumo 208 was a larger version of the Jumo 207 and it was the continued developement of the Jumo 206. Developement started in 1939 for use in the Junkers Ju90 and was continued until 1942. A few static test engines were built, but no serial production was initiated. Only 12 engines were built. Flight tests were performed on a Ju52 as a center engine.
For experimental purposes combinations of two Jumo 208 engines were studied. The intention was to create a twelve cylinder diesel engine. This double Jumo 208 was called Jumo 218. However no double engines were built.
Aircraft Types equipped with Jumo 208:
Junkers Ju86 R
The Jumo 208 should be equipped to the Ju86 R-3 surveyer aircraft.
The R-3 project was stopped before a prototype became flyable.
Possibly a Jumo 208 was mounted to a Ju86 R-1 or R-2 for flight tests
as some reports spoke of a flight test of the Jumo 208 in a Ju86R.
A Ju52 was used as testbed for the Jumo 208 test flights.
Nevertheless, the Jumo 208 was intended as an engine for the serial produced Ju52s.
Some hints are to be found about a possible equipment of the Ju90
with Jumo 208. No confirmation could be found about that plans.
As there were only built a few Jumo 208s during WWII,
it seemed, that no flight trials were performed with this engine.