Electro-Motive Diesel was a General Motors subsidiary for most of its existence, going back to the Electro-Motive Company, founded in 1922. The Electro-Motive Company began building and upgrading gasoline-powered railcars with electric transmission using engines from the Winton Engine Company. Since EMC thus became the main buyer of Winton engines, the mutual dependence of the two companies grew. Meanwhile, General Motors saw the potential of the diesel engine and was looking for partners to implement its two-stroke diesel ideas. Thus, in 1930, EMC and Winton were bought at the same time and rail vehicles with this engine were developed to series maturity.

The advantage of the two-stroke diesels was that they had one combustion stroke for each revolution of the crankshaft and therefore theoretically did twice the work per revolution compared to four-stroke engines. This led to a low power-to-weight ratio, which also benefited the Junkers two-stroke diesels used as aircraft engines in the 1930s. Since two-stroke diesels did not require inlet valves and only a Roots blower was required to scavenge the combustion gases, the number of individual parts was also reduced, which reduced manufacturing costs and simplified maintenance. In contrast, the poorer exhaust gas behavior was only relevant towards the end of the twentieth century.

It started with streamlined multiple units, the first of which was the 1933 M-10000 “City of Salina”. In the second half of the 1930s, switching locomotives and soon mainline locomotives with Winton engines followed, all of which had electric power transmission. In 1941, the company was renamed the Electro-Motive Division (EMD), becoming a wholly owned subsidiary of GM and losing the freedoms it had had until then. As early as 1938, the Cleveland Diesel Engine Division was founded to build larger two-stroke marine diesels and the Detroit Diesel Corporation to build smaller two-stroke diesels for road vehicles.

Builder's badge on a D&RGW F9

John W. Stephens III

After the TA mainline locomotive, only six of which were built, the great success of the EMD locomotives with the E and F series began in 1937 and 1939, respectively. The name of the E series passenger locomotives came from “Eighteen hundred”, since initially two Winton engines with a total of 1,800 hp were used. The F series was intended for freight trains and got its name from “Fourteen hundred” because the built-in engine initially provided 1,350 hp. Like the TA, both locomotive families had a self-supporting, streamlined carbody structure. The 567 series engines replaced the Winton 201A and were groundbreaking in their modular design, offering engines with six to 16 cylinders and in different power levels with a large number of interchangeable parts. According to their name, the engines had a displacement of 567 cubic inches (9.29 liters) per cylinder. They formed the basis for the engines of the 645 and 710 series, which were used in almost all EMD locomotives until 2014 and are still manufactured today on request for countries in which no strict exhaust gas regulations apply.

The era of the road switcher only began at EMD in 1949, when ALCO had already been offering the RS-1 for eight years. With the four-axle GP7, the six-axle SD7 and their successors, however, it was possible to make it to the top of the world within a short time. While other manufacturers were already offering engines with exhaust gas turbochargers in the 1940s, this complex technology was initially dispensed with. Thanks to the light two-stroke engines with Roots supercharger, they could initially keep up with the competition in terms of power and didn't have to struggle with the sluggish response behavior of the turbochargers of the time. It was not until 1958 that they gave in and developed the “mechanically-assisted turbocharger”, which is being connected to the crankshaft via a clutch at low engine speeds or rapid load changes and then acts like a supercharger.

In the following decades, EMD was the world market leader with the Road Switchers with the prime movers of the 567, 645 and 710 series. Since General Electric had appeared as a direct competitor in 1956, the market in North America had been divided up among themselves. It wasn't until the 1980s that GE took the lead, only just ahead of EMD. Since the 1990s, only the six-axle models of the SD series have been offered because the four-axle GP models were no longer popular with customers. Internationally, EMD locomotives were particularly popular in second and third world countries without their own production facilities, but industrialized countries also imported EMD locomotives. Other foreighn designs were also manufactured with EMD power trains, such as the 125 mph British Class 67 and the Stadler Euro, which were or are manufactured in Spain by MACOSA or its successor companies Meinfesa, Vossloh España and Stadler.

SD70ACe, the most successful variant of the SD70 series, which has sold almost 6,000 units since 1992

Tyler Silvest

The first attempt to move away from the two-stroke came in the late 1990s with the 265 series prime mover, which had 1,010 cubic inches per cylinder and as a V16 produced up to 6,300 hp. Reliability issues kept the engine from winning customer favor and the 710 series continued to be ordered. The EPA Tier 4 emission standard, which came into effect in the USA in 2015, ended the career of the 710 abruptly. In Central Europe, too, no new examples of the class 66, which was so popular with private railways, could be introduced around the same time because similar emission standards came into effect. This led to the 265 series four-stroke being brought up to date and today dubbed the 1010 series it is fitted to all EMD locos delivered in the USA. This engine has three turbochargers and state-of-the-art electronic fuel injection to comply with current emission regulations, while the 710 series two-stroke continues to be produced as an option for export.

EMD had already been sold to investors in 2005 due to GM's financial problems and was renamed Electro-Motive Diesel. In the following years the workforce increased and in 2010 EMD was sold again to Progress Rail, a subsidiary of Caterpillar. Appropriately, the company has been trading as Progress Rail Locomotive since 2016 and is still in second place worldwide behind the diesel locomotives from GE Transportation, which is now a subsidiary of Wabtec.