The EMC E2 was an American passenger-train diesel locomotive which as a single unit developed 1,800 horsepower (1,300 kW), from two (2) 900 horsepower (670 kW) prime movers. These locomotives were typically operated as a unit set (A - B - B) or (A - B - A); where the three unit lashup developed 5400 horsepower. This was almost the ideal horsepower required (6,000 horsepower or 4,500 kilowatts) for the tonnage of a 15 - 18 car passenger train, operated over the ruling grades of virtually all of the mileage between major American cities. The units were of the A1A-A1Awheel arrangement, and manufactured by Electro-Motive Corporation (EMC), later Electro-Motive Diesel (EMD) of La Grange, Illinois.
Two sets (each of three units, A-B-B) (5,400 horsepower or 4,000 kilowatts) were produced in 1937 for named passenger trains; the first set (SF-1, SF-2, and SF-3) for the City of San Francisco. These motive-power sets were jointly owned and operated by the Union Pacific Railroad, the Chicago and North Western Railway, and the Southern Pacific Railroad. The second A-B-B set (LA-1, LA-2, and LA-3) was used for the City of Los Angeles; and, was jointly owned and operated by the UP and CNW only. The first locomotive power unit was the control cab, or "A" unit, while the other two were cabless boosters, or "B" units. The control cab and booster units were designed for multiple unit operation (the first in diesel motive power). A single engine crew in the cab, remotely monitored and controlled all three motive power units from a single control station in the cab. The locomotives were diesel-electrics with two 900 hp Winton 201-A engines each, with each engine driving its own generator to power the traction motors. In addition the locomotives contained steam generators for passenger car heating. An independent auxiliary diesel powered electric generator was housed in the first car of the train consist. This car was a combination power/baggage/post office, or crew dormitory. This car provided electric power for train-line "hotel" power for their named train set(s), to include the air conditioning, dining, lounge, and entertainment. The power cars were required for these train sets because of the electrical demand of their feature cars. The E2 was the third model in a long line of passenger diesels of similar design known as EMD E-units.
The E2, along with the more-or-less simultaneous EA/EB units for the Baltimore and Ohio Railroad and the E1 units for the Atchison, Topeka and Santa Fe Railway, represented an important step in the evolution of the passenger diesel locomotive. While the EA, E1 and E2 were each built for a specific railroad and train, they were largely identical mechanically and were a step further away from the concept of custom-built motive power, integrated into a particular streamliner; and towards mass-produced standardized locomotives. This transition was achieved with the E3, E4, E5, and E6, EMC (later EMD)'s next models.
