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performance calculations for the BMW VI 7.3z aircraft engine

BMW VI 7.3z liquid-cooled 12 -cylinder V-engine 690 [hp] (514.5 KW)

introduction : 1934 country : Germany importance : ***

applications : Heinkel He.70D

normal rating : 690 [hp](514.5 KW) at 1650 [rpm] at 0 [m] above sea level

take-off power : 750 [hp] (559.3 [KW]) at 1700 [rpm]

no reduction, direct drive, valvetrain : overhead camshaft

weight engine(s) dry : 510.0 [kg] = 0.99 [kg/KW]

General information :

fuel system : 2x Zenith 60 DCL carburettor fuel type : octane grade no. 87

oil system : engine starter type :

bore : 160.0 [mm] stroke : 190 / 199 [mm]

valve inlet area : 39.1 [cm^2] one inlet and one exhaust valve in cylinder head

gas speed at inlet valve : 38.7 [m/s]

compression ratio: 7.30 :1

stroke volume (Vs displacement): 46.950 [litre]

compression volume (Vc): 7.457 [litre]

total volume (Vt): 54.433 [litre]

engine height : 110 [cm] engine width : 86 [cm]

calculated engine length: 1.81 [m]

specific power : 11.0 [kW/litre]

torque : 2978 [Nm]

engine weight/volume : 10.9 : [kg/litre]

average piston speed (Cm): 10.7 [m/s]

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intake manifold absolute pressure (MAP) at 0 [m] altitude Pi : 0.90 [kg/cm2]

mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 6.93 [kg/cm2]

compression pressure at 0 [m] altitude Pc: 10.79 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 43.10 [kg/cm2]

exhaust pressure at 0 [m] Pu : 3.52 [kg/cm^2 ]

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compression-start temperature at 0 [m] Tic: 367 [°K] (94 [°C])

compression-end temperature at 0 [m] Tc: 586 [°K] (313 [°C])

average engine wall temperature at 0 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 0 [m] Tec: 2325 [°K] (2052 [°C])

polytroph combustion temperature at 0 [m] Tep : 2340 [°K] (2067 [°C])

estimated combustion temperature at 0 [m] Te (T4): 2291 [°K] (2018 [°C])

polytrope expansion-end temperature at 0 [m] Tup: 1156 [°K] (883 [°C])

exhaust stroke end temperature at 0 [m] Tu: 1073 [°K] (800 [°C])

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Thermal efficiency Nth : 0.392 [ ]

Mechanical efficiency Nm : 0.757 [ ]

Thermo-dynamic efficiency Ntd : 0.296 [ ]

design hours : 672 [hr] time between overhaul : 171 [hr]

dispersed heat by cooling fluids at 1650.00 [rpm] at 0 [m]: 145.41 [Kcal/minuut/litre]

fuel consumption optimum mixture at 1650.00 [rpm] at 0 [m]: 207.47 [kg/hr]

specific fuel consumption thermo-dynamic : 203 [gr/epk] = 272 [gr/kwh]

estimated specific fuel consumption (cruise power) at 0 [m] optimum mixture : 313

[gr/kwh]

specific fuel consumption (volume*rpm) at 1650 [rpm] : 426 [gr/kwh]

estimated specific oil consumption (cruise power) : 9 [gr/kwh]

Literature :

Wikipedia

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. For copyright on drawings/photographs/

content please mail to below mail address

(c) B van der Zalm 28 November 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4

notes :

MEP is low compared to compression ratio.