RE: Pfalz DIII resources -- Photos, Drawings, Plans, etc.
I'm pretty sure that only Mercedes had an in-line 6 which was used in the Pfalz, Albatross etc.
However throughout the war they were up-grading the engine to have more power, so that the later engines were different models (versions) of the M-B. I'm not sure whether they did it by increasing the displacment, which would have been the easiest way to do it. I'll try and find out.
alan