Locomotive main engines in use today


Locomotive prime movers are the engines of all diesel-electric locomotives and form the heart of the entire locomotive. The main motors provide enough power to pull both the locomotive and any freight cars attached to it, while producing enough additional power to meet the power requirements of the various locomotive systems such as headlights, computer systems and cooling fans.

A rebuilt EMD 16-cylinder 645 prime mover is installed on a Norfolk Southern SD40-2 in Altoona, Pennsylvania. Photograph by Chris Guss

Each prime mover can be rated at different power levels or built with a different number of cylinders. Some can be built with different features to increase power, such as a turbocharger.

Since the same prime mover can produce different amounts of power, a locomotive design is designed to support a prime mover producing a particular horsepower. From the cooling system to the traction motors below, everything is balanced to work well with specific horsepower.

On Class I railroads, listings are primarily a two-builder affair, with Wabtec (formerly General Electric) and EMD locomotives dominating the Class I rosters. Wabtec has used the four-cycle 7FDL design since the mid-1950s, then transitioned to the GEVO prime mover nationwide in the mid-2000s. Class I iron currently use the 16-cylinder 7FDL and 12-cylinder GEVO-12 main engines in their GE locomotives.

EMD locomotives on Class I railroads use four different engine designs, the 567, main engines 645, 710 and 1010J. The first three are two-cycle designs with the 567 installed in new locomotives from the mid-1930s through the mid-1960s. It is the least common in the industry, all remaining prime movers on the railroads of class I typically using newer 645 engine components in-house.

EMD’s 645 prime mover replaced the 567 and was used until the early 1980s when the 710 was introduced. The 710 also suffered the same fate as the 7FDL when emissions requirements forced the prime mover into national retirement, being replaced by the 12-cylinder 1010J in 2015. It is the first four-stroke engine used in EMD locomotives.

Locomotive main engines: pale green painted engines sit on blocks in a factory.
New 12-cylinder GEVO-12 main engines await installation at Wabtec’s plant in Fort Worth, Texas. Photograph by Chris Guss

Class I railroads have a mix of EMD prime mover sizes in the 567, 645, and 710 series, ranging from 8, 12, 16, and 20 cylinders in their fleets. Union Pacific also has a small fleet of rebuilt EMD locomotives with Caterpillar 3512C HD 12-cylinder engines.

Gensets are less common today on Class I railroads, and the remaining locomotives use engines from different manufacturers. National Railway Equipment generator sets are equipped with Cummins 6 cylinder QSK19 engines and Railpower generator sets are equipped with 8 cylinder Deutz V-8 2015.


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