GR-7 Turbojet Engine Specifications
Turbo make: Cummins VT-50 Turbo AR#10076 (From 14 liter 6-cyl. diesel engine)
Turbo inducer diameter: 75 mm
Turbo exducer diameter: 90 mm
Weight of rotating assembly: 3 pounds - 10.5 ounces
Combustor type: Side entry single can evaporative combustor
Combustor metal type: Stainless steel - SAE grade 304
Combustor length - combustor end plate to outside of elbow: 55.88 cm
Combustor elbow inside/outside radius: 52 mm/127 mm
Flame tube ID: 97.3 mm actual (97.5 mm calculated from GR-1 formula)
Flame tube length from evaporator base: 292 mm actual (288.75 mm calculated value from GR-1 formula)
Combustion chamber ID: 147 mm actual (157.5 mm calculated / 7% difference)
Flame tube bypass area: 17.75 sq cm actual (27 sq cm calculated - GR-1 formula not applicable due to evap system modification)
Flame tube hole area: 29.282 sq cm actual (30 sq cm calculated from the GR-1 formula)
Flame tube holes: 112 holes actual (90 holes calculated / 20% difference):
Primary holes: 84 holes @ 7/32” (0.556 cm dia & 0.243 sq cm area for a total of 20.412 sq cm)
Secondary holes: 28 holes @ 1/4” (0.635 cm dia & 0.317 sq cm area for a total of 8.87 sq cm)
Evaporator air induction area: 12.8 sq cm (on injector base’s side)
Evaporator tube inside diameters: 1” x .065” (large tube - 22.1 mm ID) and 5/8” x .065” (small tubes – 12.55 mm ID)
Evaporator tube dimensions: The “trunk” is 11.45 cm long and the “legs” are 7.95 cm long. The outermost part of the legs are 3.8 cm from center of the trunk (radius).
Evaporator tube end-gap to top of injector base: 2.85 cm.
Evaporator tube combined outlet area: 3.71 sq cm
Evaporator base orifice diameter: 19.2 mm
Evaporator orifice pass through area (with nozzle inside): 1.76 sq cm
Oil type: 5-30 synthetic motor oil
Oil pressure: 35 PSI regulated
Hydrostatic oil circulation: 1.1 gallon per minute cold and 1.6 gallons when hot.
Oil tank: 1.6 liters in volume (1.7 quarts)
Total system oil volume: 3.3 liters (3.5 quarts)
Starting system: Twin 400 watt 3-phase starter motors (2 x 1/2 HP)
Starter motor speed: 30,000 unloaded (24,000 under load)
Starter gear ratio: (36 main/26 spur) 1.38:1
System current draw at starting: +/- 85 amps @ 13 volts DC
System current draw while running: 17.5 amps @ 13 volts DC
Fuel type: #2 diesel, kerosene or Jet-A
Fuel pressure: 95 PSI
Fuel consumption: 4 GPH at idle and 13 GPH at full power
Max engine RPM: 66,500 RPM (1450 FPS tip speed)
Idle thrust: 10 pounds static at 31,000 RPM
Full thrust: 51 pounds static at 66,000 RPM
Idle combustor pressure (P2): 6 PSI
Full combustor pressure (P2): 24 PSI
Idle EGT (TOT): 950* F
Full power EGT (TOT): 1200* F
Compression ratio: 2.7:1
Jet nozzle diameter: 72 mm
Gas velocity out of nozzle at full throttle: 1300 FPS
Mass flow at full throttle: 1.33 Lbs/Sec
Engine dry weight: 156 pounds
Engine dimensions (without jet nozzle): 26” long x 18” wide x 20.57” high
Additional Info:
Torque setting of comp. wheel Allen nut: 30 Foot-pounds (24 ft/lbs for stock nut)
Mellet part number for turbine wheel: 1200-050-436
Mellet part number for compressor wheel: 1200-050-428
Possible “bolt-on” sub for VT-50 is Holset HT3B
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