MTH ELECTRIC TRAINS

The GP20 was a trendsetter, popularizing two features that would become virtually standard on American diesels: a low short hood that gave the engineer a wide panoramic view, and turbocharging.

Introduced by the Electro-Motive Division of General Motors in 1959, the GP20 was the first of EMD’s hugely popular “Geeps” (GP, or “general purpose” diesels) to feature a low short hood in front of the cab as standard equipment. The high short hood of previous Geeps — with a lot of metal between the crew and any potential collision — had felt familiar and safe to engineers who only recently graduated from steam power, and were used to looking out past an engine’s nose to see the track. The unobstructed view from the cab of the GP20, however, was not hard to get used to.

Turbocharging was a way to get more power output from the same size diesel motor. Fairly early in the history of internal combustion motors, designers found that increasing the pressure of the incoming air produced an increase in horsepower, sometimes as much as 50%. In the beginning, this was accomplished with a mechanical air compressor, or blower, geared to the motor — which, however, put an extra load on the motor.

Much later, someone thought to put a turbine in the exhaust pipe of an engine, and use exhaust gases to spin the turbine and power an air compressor, basically for free. What finally got EMD to try turbocharging on its diesels was a push from a major customer, the Union Pacific, which began experimenting with turbochargers in the mid-1950s.