AIRCRAFT INVESTIGATION
Performance calculations for the Mercedes D.IIIa 175PS WWI aero engine
Mercedes D.IIIa
liquid-cooled 6 -cylinder inline engine 175 [hp](128.7 KW)
introduction : 1917 country : Germany importance : ****
applications : Pfalz D.XII
normal rating : 175 [hp](128.7 KW) at 1400 [rpm] at 0 [m] above sea level
no reduction, direct drive, valvetrain : SOHC
general information :
Development of the basic design led to the slightly modified 170 hp D.IIIa, which took over on the production lines in June 1917. The main change was to change the piston profile to have a flat head instead of the former concave one, thereby slightly increasing maximum compression. Other changes were mainly in design details, notably a redesigned crankcase and new carburettor. Many of the accessories were also redesigned or moved around on the engine. This model was produced only briefly, for use on the Albatros D.III but there are indications that possibly some early Albatros (Alb.) made Fokker D.VII's were also equipped but probably had the engines upgraded or replaced as quickly as possible. This engine has been referred to in post-war British analysis as generating 180 hp.
weight engine(s) dry : 297.0 [kg] = 2.31 [kg/KW]
bore : 140.0 [mm] stroke : 160.0 [mm]
Mechanical efficiency/mean pressure correction factor : 0.609 [ ]
Altitude influence factor > cm : 0.17 [ ]
compression ratio: 4.64 :1
calculated compression ratio : 4.64 : 1
published volume (displacement): 14.778 [litre]
calculated stroke volume (Vs) : 14.778 [litre]
compression volume (Vc): 4.060 [litre]
total volume (Vt): 18.838 [litre]
power / stroke volume (litervermogen Nl): 8.7 [kW/litre]
torque : 878 [Nm]
engine weight/volume : 20.1 : [kg/litre]
average piston speed (Cm): 7.5 [m/s]
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intake pressure at 0 [m] altitude Pi : 0.95 [kg/cm2]
mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 5.97 [kg/cm2]
compression pressure at 0 [m] altitude Pc: 6.81 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 27.23 [kg/cm2]
exhaust pressure at 0 [m] Pu : 3.80 [kg/cm^2 ]
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compression-end temperature at 0 [m] Tc: 580 [°K] (306 [°C])
caloric combustion temperature at 0 [m] Tec: 2182 [°K] (1908 [°C])
polytropic combustion temperature at 0 [m] Te (T4): 2313 [°K] (2040 [°C])
exhaust temperature at 0 [m] Tu: 1346 [°K] (1073 [°C])
emergency/TO rating can be increased with higher [rpm}
(emergency/take off) rating at 1533 [rpm] at sea level : 195 [pk]
Thermal efficiency Nth : 0.319 [ ]
Mechanical efficiency Nm : 0.791 [ ]
Thermo-dynamic efficiency Ntd : 0.252 [ ]
design hours : 1237 time between overhaul : 103
fuel consumption optimum mixture at 1400.00 [rpm] at 0 [m]: 48.10 [kg/hr]
specific fuel consumption thermo-dynamic : 251 [gr/epk] = 341 [gr/kwh]
specific fuel consumption (cruise power) at 0 [m] optimum mixture : 347 [gr/kwh]
estimated sfc (cruise power) at 3000 [m] rich mixture : 362 [gr/kwh]
specific fuel consumption at 0 [m] at 1400 [rpm] optimum mixture : 374 [gr/kwh]
estimated specific oil consumption (cruise power) : 28 [gr/kwh]
Literature : wikepedia
DISCLAIMER Above calculations are based on published data, they must be
regarded as indication not as facts.
Calculated performance and weight may not correspond with actual weights
and performances and are assumptions for which no responsibility can be taken.
Calculations are as accurate as possible, they can be fine-tuned when more data
is available, you are welcome to give suggestions and additional information
so we can improve our program.
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(c) B van der Zalm 13 december 2018 contact : bvanderzalm@ziggo.nl python 3.4.1