The Mercedes D.IVa was a German six-cylinder, water-cooled, inline engine developed in 1917 for use in aircraft and built by Daimler Motoren Gesellschaft (DMG).[1]
The D.IVa replaced the failed Mercedes D.IV inline eight-cylinder engine. The D.IVa was primarily used to power bombers and large reconnaissance aircraft. Unlike most German designs, the D.IVa was relatively advanced, including four valves per cylinder actuated by a SOHC valvetrain, the same "single-camshaft" arrangement that had also been used on the earlier two-valve per cylinder D.I through D.IIIa powerplants.
Designed specifically to be installed in the fuselage, the engine featured a number of design elements intended to reduce its width. For instance, the carburetor was placed behind the engine, feeding fuel to the cylinders via a long tubular intake manifold. This had the disadvantage of poor fuel distribution. Two versions of the engine were produced in mirror copies, running in opposite directions.