Worlds Most Powerful Diesel Locomotives
The EMD SD90MAC-H is rated at 6000hp and has 200,000 lbs of starting tractive effort. The GE AC6000CW, although having the same 6000hp, has been quoted in some sources as having less starting tractive effort (185,000) than the EMD model. Other sources quote the AC6000CW and the SD90MAC-H being equal in both starting TE and HP. In practical terms, GE is the winner, as there were more AC6000CW units built and still in service. The SD90MAC has a bit of a bad reputation due to initial reliability issues. UP gave up over 40 of their 8500-series units to EMD leaser service (reporting mark EMLX), with all of them going to KCS for a while. KCS has turned them back over to EMD’s leasing arm and there is no word as to what road they will be leased to next. As far as I can tell, the AC6000CW fleet still runs with their original owners, with no word as to how reliable they are.
However, the SD90MAC and AC6000CW are only equipped with a single diesel engine. In 1969, EMD built the dual-engine DDA40X ”Centennial” locomotives for the Union Pacific. These locomotives were the largest and heaviest locomotives ever built, with 6600 horsepower. However, they were geared for high-speed freight use and only had 136,000 lbs of starting TE. With exception of the UP 6936 in the UP heritage fleet, all these locos have been scrapped or donated to museums.
Railroads today tend to shy away from high-powered locos, as the loss of one high-power loco in a consist means the loss of a lot of the train’s available power. For example, a railroad can specify that a train have 12000 horsepower available from its locomotives. They can put a pair of 6000hp locomotives on it, three 4000hp locos, or perhaps four 3000 hp units. If one of the 6000hp units fail, the train has lost half its available power. If a 4000hp loco in a three-loco consist fails, the train still has two-thirds power available. See how that works?