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Mercedes D.IV
1915 - 1916



The Mercedes D.IV is an 8-inline-cylinder aircraft engine manufactured by the German company Daimler Motoren Gesellschaft during the First World War. The D.IV was the first mass-produced German engine equipped with a propeller reduction drive. Its construction scheme derived from the previous and very successful D.III, from which it differed for the larger number of cylinders (from 6 to 8). The engine overcame the acceptance test in December of 1915, but it was produced in only 429 copies because of its poor reliability, mainly due to the fragility of the crankshaft for its excessive length. Because of this the D.IV was soon replaced by a completely redesigned engine, the D.IVa with 6 cylinders. The designation similar between the two engines is due to the rigid classification then in use in Germany, based on groups of power output by (I to VI), in which the first letter indicates the manufacturer.

Technical specifications

ManufacturerDaimler Motoren Gesellschaft, Stuttgart-Untertürkheim, Germany, 1915
TypeMercedes D.IV
Descriptionaircraft engine with 8-inlne cylinders, aluminium alloy crankcase with 9 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
Stroke160 mm
Bore140 mm
Displacement19770 cm³
Compression ratio4.6
Power232 hp at 1440 rpm (maximum output at sea level); 210 hp at 1300 rpm (max. service output at sea level)
Specific consumption230 g/hp/h
Specific power12.1 hp/litre
Valvetrain system2 overhead valves per cylinder controlled by an overhead gear-driven camshaft
Fuel feeding systemwith two single-barrel gasoline carburetors
Ignition systemtwo spark plugs per cylinder fed by two high voltage magneto distributors Bosch HL8
Cooling systemliquid-fed by a centrifugal pump
Lubrication systemforced by means of a 4-cylinder reciprocating pump
Length1990 mm
Width600 mm
Height1040 mm
Weight410 kg
Mass-to-power ratio1.71 kg/hp
Propeller transmission ratio1.38:1 by means of a reduction drive with a pair of spur gears


AEG C.V   (reconnaissance aircraft)

AEG G.III   (bombardier)

AEG G.IV   (bombardier)

AEG G.V   (bombardier)

AEG R.I   (bombardier)

AGO C.II   (reconnaissance aircraft)

AGO C.VIII   (reconnaissance aircraft)

Albatros C.V   (reconnaissance aircraft)

Gotha G.II   (bombardier)

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 - Museo Motori UNIPA

 - Museo Motori UNIPA

 - Museo Motori UNIPA
Testi e immagini di Giuseppe Genchi
Sito realizzato da Pasquale Pillitteri