EMD SD90MAC

EMD SD90MAC and SD9043MAC
Union Pacific 8540, an SD90MAC Phase II
Type and origin Power type Diesel-electric Builder Electro-Motive Diesel (EMD) Model SD90MAC Build date 1995–2000 Total produced 657
Specifications Configuration: ​  • AAR C-C  • UIC Co’Co’ Gauge 4 ft 8+1⁄2 in (1,435 mm) Wheel diameter 45 in (1,100 mm) Length 80 ft 2 in (24.43 m) Loco weight 415,000 lb (188,000 kg) (SD9043MAC) and 425,000 lb (193,000 kg) (SD90MAC-H & SD90MAC-H2) Fuel capacity 5,000 US gal (19,000 L; 4,200 imp gal) Sandbox cap. 40 cu ft (1.1 m3) Prime mover EMD 16-710 G3C-T1 and 16-265H RPM range 225-1,000 rpm Engine type V16 diesel Traction motors 6 Siemens 1TB2830 AC motors Cylinders 16 Cylinder size 10.45 in × 11.80 in (265 mm × 300 mm)
Performance figures Maximum speed 70 mph (113 km/h) Power output SD9043MAC: 4,300 hp (3,210 kW) SD90MAC: 6,000 hp (4,470 kW) Tractive effort Small engine (SD9043MAC): 185,000 lbf (820 kN) starting, 147,000 lbf (650 kN) continuous Large engine (SD90MAC-H and SD90MAC-H2): 200,000 lbf (890 kN) starting, 165,000 lbf (730 kN) continuous

The EMD SD90MAC is a model of 6,000 hp (4,470 kW) C-C diesel-electric locomotive produced by General Motors Electro-Motive Division (EMD). It is, with the SD80MAC, the largest single-engined locomotives produced, and among the most powerful diesel-electric locomotives made by EMD, surpassed only by the dual-engined DDA40X.

The SD9043MAC is the 4,300 hp (3,210 kW) variant, using a 16-cylinder 710G engine instead of the H-engine, which was originally intended as a temporary alternative while EMD tried to solve the H-engine's issues. However, the accompanying upgrade program was never utilized by its customers.

The SD90MACs features include radial steering trucks with AC traction motors and an isolated safety cab which is mounted on shock absorbers to lessen vibrations in the cab. The SD90/43MACs and early 265H equipped SD90MACs are built with the WhisperCab like the SD70 series and SD80MAC, while later SD90MACs were equipped with the Phase 2 safety Cab with notches on the side of the nose similar to the SD70ACe. The SD90MAC, like the SD80MAC, SD70ACe, and SD70M-2, has a wide radiator section, nearly the entire width of the locomotive, which along with their size makes them easy to spot.

As of 2025, most SD90MACs have been rebuilt, being the 4300hp SD90/43MACs. The SD90MACs equipped with the 16 cylinder 265H have long been scrapped. Norfolk Southern had rostered 110 SD90MAC locomotives purchased or traded from Union Pacific or the CIT Group respectively, that have now all been rebuilt as EMD SD70ACU locomotives. Canadian Pacific has also converted their small fleet of long-stored SD90/43MACs into SD70ACUs as well.