SD90MAC Diesel Locomotive

Prototype Information

The EMD SD90MAC hit the rails in 1995 as Electro-Motive’s bold push for a new generation of high-horsepower, AC-traction locomotives. Powered by the experimental 6,000-horsepower 16-cylinder 265H engine, it aimed to dominate heavy freight service with unmatched muscle and modern electronics. However, persistent reliability problems with the 265H engine quickly hurt its reputation.

To keep sales moving, EMD released the SD9043MAC, a 4,300-horsepower version using the proven 710G engine but built on the same frame and carbody. Railroads like Union Pacific and Canadian Pacific bought hundreds of these “convertible” units, expecting to upgrade them later—an upgrade that never came.

Although the SD90MAC fell short of its 6,000-horsepower promise, it paved the way for future designs like the SD70ACe, carrying forward valuable lessons in AC traction, electronics, and high-horsepower locomotive engineering.