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Type and origin
Power typeDiesel-electric
BuilderGeneral Motors Electro-Motive Division (EMD)
Build dateNovember 1959 to April 1962
Total produced260
 • UICBo′Bo′
Gauge4 ft 8+12 in (1,435 mm)
Length56 ft 2 in (17.12 m)
Width10 ft 3 in (3.12 m)
Height14 ft 6 in (4.42 m)
Loco weight240,000 lb (108,862 kg)
Fuel capacity2,350 US gal (8,896 L; 1,957 imp gal)
Lubricant cap.227 US gal (859 L; 189 imp gal)
Coolant cap.220 US gal (833 L; 183 imp gal)
Sandbox cap.18 cu ft (0.51 m3)
Prime moverEMD 16-567D2
Engine typeTwo-stroke V16 diesel
Displacement9,072 cu in (148.66 L)
GeneratorEMD D-22
Traction motorsEMD D47 (4) or D57 (4)
Cylinder size8+12 in × 10 in (216 mm × 254 mm)
TransmissionDiesel electric
Loco brakeSchedule 24RL or 26L Straight air, optional: dynamic
Performance figures
Maximum speed65 mph (105 km/h)
Power output2,000 hp (1.5 MW)
Tractive effortStarting: 63,375 lbf (28,746 kgf) Continuous: 45,000 lbf (20,412 kgf) @9.3 mph (15.0 km/h)
LocaleUnited States

An EMD GP20 is a 4-axle diesel-electric locomotive built by General Motors' Electro-Motive Division between November 1959 and April 1962. Power was provided by an EMD 16-567D2 16-cylinder turbocharged engine which generated 2,000 horsepower (1,500 kW). EMD was initially hesitant to turbocharge their 567-series diesel engine, but was spurred on to do so following successful tests made by Union Pacific in the form of UP's experimental Omaha GP20 units. 260 examples of EMD's production locomotive model (with the EMD turbocharger) were built for American railroads.

The GP20 was the second EMD production locomotive to be built with an EMD turbocharged diesel engine, sixteen months after the six-axle (C-C) model SD24. Power output of the turbocharged SD24 was 33 percent higher than the 1,800 hp (1,340 kW) of the concurrent Roots blower-equipped SD18s with the same engine displacement, 400 hp (298 kW) per axle, but the power output of the turbocharged GP20 was only 11 percent higher than the 1,800 hp (1,340 kW) of the concurrent Roots blower-equipped GP18s with the same engine displacement 500 hp (373 kW) per axle, due to the limitations of the traction motors then available. Nevertheless, the turbocharged GP20 provided full rated power at all altitudes, which the Roots-blown GP18 could not provide.

EMD-type Turbo-Compressor (Turbocharger)[edit]

The turbocharger was the then-new EMD mechanically assisted turbo-compressor. During engine startup, and at lower power levels, during which there is not sufficient exhaust heat energy to drive the turbine fast enough for the compressor to supply the air necessary for combustion, the engine drives the compressor through a gear train and a freewheel. At higher power levels, the freewheel is disengaged, and the turbo-compressor operates as a true turbocharger. It is possible for the turbo-compressor to revert to compressor mode momentarily during commands for large increases in engine power. Turbocharging provides higher horsepower and good running characteristics at all altitudes. Turbocharging also improves fuel consumption and reduces emissions.

Previous Union Pacific experiments with turbocharging had utilized multiple Elliot[1] or Garrett AiResearch turbochargers feeding the usual pair of Roots blowers. EMD's mechanically assisted turbocharger eliminated the need for the pair of Roots blowers and also integrated the turbocharging function from two (Elliot) or four (AiResearch) smaller add-on turbochargers into one much larger, turbo-compressor (turbocharger) with intercooling.

The introduction of the EMD-type turbocharger was successful and all subsequent GP series were offered with this turbocharger, although not all models within a series were offered with turbocharging (e.g., the 38 models were Roots-blown).

Original buyers[edit]

Railroad Quantity Road numbers Notes
Electro Motive Division (demonstrators)
to Southern Pacific 7234–7237
Atchison, Topeka and Santa Fe Railway
Chicago, Burlington and Quincy Railroad
to Burlington Northern Railroad 2036–2071
Great Northern Railway
High short hood; to Burlington Northern Railroad 2000–2035, 1700 gallon fuel tanks
New York Central Railroad
no dynamic brake; to Penn Central 2100-2112; to Conrail same numbers
Southern Pacific Company
St. Louis Southwestern Railway
Union Pacific Railroad
Western Pacific Railroad
High short hood; Second Order used Blomberg B trucks from traded-in FTs
Total 260


WP #2001, the first production GP20, leads a special train in 2009. Note the high nose on the short hood.
  • Western Pacific 2001, the very first GP20 built, is preserved at Western Pacific Railroad Museum at Portola, CA.
  • KLIX 2003, originally Cotton Belt 815, is being stored at the Arkansas Railroad Museum in Pine Bluff, AR.
  • Midland Railway 4079, originally Southern Pacific 7229, is on The Midland Railway in Baldwin City, Kansas.


  1. ^ "Elliot Turbochargers". Sinor Engine Company, Inc. Archived from the original on 2012-03-22.

External links[edit]