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Mercedes D.IVa
1916 - 1918



The Mercedes D.IVa was an aircraft engine with six-cylinder in line produced by the German company Daimler-Motoren-Gesellschaft in 1916 to replace, in the range 200-299 hp ("klasse IV"), the previous disastrous Mercedes D.IV with 8 cylinders. The D.IVa took up most of the constructive solutions of the Mercedes engines, with a new 4-valves per cylinder arrangement and a particular attention to the reduction of the frontal area. To this purpose, the carburetor, normally mounted on one side, was placed behind the engine and connected to the cylinders through a long intake manifold. This, in turn, entailed the disadvantage of not distributing evenly between the cylinders the air-fuel mixture. The D.IVa was produced in various versions, for a total of 4550 samples, and developed until the end of the war. The aspirated versions were produced in two series, with different direction of rotation, for the use on twin-engine aircraft; later, in the search for ever greater power at high altitude, some supercharged versions with centrifugal multistage compressors were developend in cooperation with various manufacturers: Schwade & Co, Brown Boveri, AEG and Siemens-Schuckert. Finally, an experimental version with direct fuel injection was developed in 1918 in collaboration with Junkers.

Technical specifications

ManufacturerDaimler Motoren Gesellschaft, Stuttgart-Untertürkheim, Germany, 1916
TypeMercedes D.IVa
Descriptionaircraft engine with 6-inline cylinders, aluminium alloy crankcase with 7 main bearings, stell-made cylinder and heads, cooling jackets in thin-walled welded steel, steel-made pistons from of two part (top and skirt) screwed and welded
Stroke180 mm
Bore160 mm
Displacement21700 cm³
Compression ratio4.82
Power260 hp at 1450 rpm (max. output at sea level)
Specific fuel consumption230 g/hp/h
Specific power12.7 hp/litre
Valvetrain system2 overhead valves per cylinder controlled by an overhead gear-driven camshaft
Fuel feeding systemwith a single-barrel gasoline carburetor
Ignition systemtwo spark plugs per cylinder fed by two high voltage magneto distributors Bosch Zh6, firing order: 1-5-3-6-2-4
Cooling systemliquid-fed by a centrifugal pump
Lubrication systemforced by means of a 4-cylinder reciprocating pump
Weight410 kg
Mass-to-power ratio1.50 kg/hp


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Friedrichshafen G.III (bombardier)

Gotha G.III (bombardier)

Gotha G.V (bombardier)

Rumpler C.IV (reconnaissance aircraft)

Zeppelin-Staaken R.VI (bombardier)

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Testi e immagini di Giuseppe Genchi
Sito realizzato da Pasquale Pillitteri