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performance calculations for the Wright R-790 J-4 Whirlwind aircraft engine

Wright R-790 J-4 Whirlwind air-cooled 9 -cylinder radial engine 220 [hp](164.1 KW)

introduction : 1924 country : U.S. importance : ****

applications : Fokker F.VIIa/3m

normal rating : 220 [hp](164.1 KW) at 2000 [rpm] at 0 [m] above sea level

no reduction, direct drive, valvetrain : pushrod-actuated

fuel system : oil system :

weight engine(s) dry : 236.0 [kg] = 1.44 [kg/KW]

bore : 114.0 [mm] stroke : 140.0 [mm]

valve inlet area : 19.8 [cm^2] one inlet and one exhaust valve in cylinder head

gasspeed at inlet valve : 33.9 [m/s]

throttle : 90 /100 open, mixture :13.0 :1

compression ratio: 5.10 :1

published volume (displacement): 12.910 [litre]

compression volume (Vc): 3.137 [litre]

total volume (Vt): 15.998 [litre]

diam. engine : 114 [cm]

engine length: 0.86 – 1.02 [m]

specific power : 12.7 [kW/litre]

torque : 783 [Nm]

engine weight/volume : 18.3 : [kg/litre]

average piston speed (Cm): 9.3 [m/s]

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intake pressure at 0 [m] altitude Pi : 0.88 [kg/cm2]

mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 6.27 [kg/cm2]

compression pressure at 0 [m] altitude Pc: 6.75 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 26.96 [kg/cm2]

exhaust pressure at 0 [m] Pu : 3.46 [kg/cm^2 ]

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compression-start temperature at 0 [m] Tic: 355 [°K] (82 [°C])

compression-end temperature at 0 [m] Tc: 523 [°K] (250 [°C])

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

caloric combustion temperature at 0 [m] Tec: 2132 [°K] (1859 [°C])

polytroph combustion temperature at 0 [m] Tep : 2089 [°K] (1815 [°C])

estimated combustion temperature at 0 [m] Te (T4): 2088 [°K] (1815 [°C])

polytrope expansion-end temperature at 0 [m] Tup: 1164 [°K] (891 [°C])

exhaust stroke end temperature at 0 [m] Tu: 1111 [°K] (838 [°C])

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emergency/take off rating at 2200 [rpm] at sea level : 238 [hp]

Thermal efficiency Nth : 0.335 [ ]

Mechanical efficiency Nm : 0.758 [ ]

Thermo-dynamic efficiency Ntd : 0.254 [ ]

design hours : 2254 [hr] time between overhaul : 66 [hr]

dispersed engine heat by cooling air : 3600.76 [Kcal/minuut/m2]

required cooling surface : 8.73 [m2]

weight cooling ribs : 92.15 [kg]

fuel consumption optimum mixture at 2000.00 [rpm] at 0 [m]: 52.87 [kg/hr]

specific fuel consumption thermo-dynamic : 237 [gr/epk] = 318 [gr/kwh]

estimated specific fuel consumption (cruise power) at 0 [m] optimum mixture : 320 [gr/kwh]

estimated sfc (cruise power) at 2375 [m] rich mixture : 325 [gr/kwh]

specific fuel consumption at 0 [m] at 2000 [rpm] with mixture :13.0 :1 : 322 [gr/kwh]

estimated specific oil consumption (cruise power) : 18 [gr/kwh]

Literature :

Wright R-790 Whirlwind - Wikipedia

Wright J-4 Whirlwind Archives - This Day in Aviation

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 16 March 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4

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