There have been a number of big, powerful diesel locomotives with the modern horsepower race. Here's my suggestions for a number of the biggest and most powerful locomotives in the US (and other parts of the world, too). This list of monsters includes locos from UP's roster of massive diesels and a few other giants that are needed in game. 1.) UP Gas Turbines (GTELs) (technically these are not diesel locomotives, but I had to include them in this suggestion for obvious reasons): If any locomotive screams big and powerful, these are the ones! They literally screamed, since the GTELs were powered by gas turbines (basically jet engines)! UP rostered the largest number of Gas Turbine locomotives, although the Swiss and British also had a couple designs. Besides the 1948 prototype #50, UP had three production models: -10 1st Generation GTELs #51-60 with 8 axles -15 2nd Generation "Veranda" Turbines #61-75 with 8 axles -3rd Generation "Big Blow" 3-unit Turbines #1-30 with 6 axles The 1st two models were rated at 4500HP, which was a lot compared to an EMD GP7 (1500HP) or GP9 (1750HP). The monstrous 3rd Gen. GTELs measured 179' long with both units and the tender and were rated at a whopping 8500HP (at certain altitudes, these beasts could even produce 10000HP if the electrical system could handle it)! UP retired their Turbines by 1970 because they were not very fuel-efficient. Two of UP's giant 3rd Gen GTELs have been preserved in museums. I've actually seen the one in Ogden, UT. Wow! It's insane how collosal that thing is! 2.) Alco Century 855 (C855) (#60, 61, and 60B): UP had the American Locomotive Company (Alco) build a trio of massive, twin-engined, 5500HP locomotives in 1964. The Alco-built giants were not so successful and were scrapped by 1972. There were 2 A-Units and a B-Unit. 3.) GE U50 (UP #31-53; SP #8500-8502): UP contracted GE to build 26 enormous U50s. The Southern Pacific RR also ordered 3 of the units. These beasts were equipped with two GE FDL-16 prime movers that together produced 5000HP. When UP began scrapping their earlier Turbine units, they reused the trucks for these big GE diesels. Due to the trucks cracking, the U50s were all scrapped by 1977. 4.) GE U50C (#5000-5039): UP's second run of GE giant diesels were their 40 U50Cs. These units used a 12-Cylinder version of GE's FDL prime mover. The U50Cs differed from the U50s by their six-axle trucks, which came from the 3rd Gen GTELs. Unfortunately, becuase of the aluminum (as opposed to copper) wiring, the U50Cs were not reliable, and many overheated or suffered from electrical fires. The U50Cs were all scrapped by 1978. -5.) EMD DD35 (UP #72B-98B; SP #8400-8402) and DD35A (UP #70-84): EMD built 27 DD35s for UP in 1963-65. These units were basically 2 GP35s put together on one frame. They produced 5000HP and were often run in A-B-B-A sets with a GP35 on each end, sandwiching two of the DD35s. SP also ordered a trio of the DD35 units, for a total of 30 units built. EMD also built 15 DD35A units. These were the same as the DD35s, just with cabs. UP was the only railroad to order these. Initially, the DD35s and DD35As were unreliable, but that was because sand got into the electrical systems. UP placed the sand boxes on the outside of the engine, and this fixed some of the issues, but as these had older-style electronic systems, they were still problematic. The DD35s lasted until 1977, and the DD35As lasted until 1981. 6.) EMD DDA40X "Centennial" (#6900-6936): UP's most successful of their giant diesels was their group of 47 DDA40Xs. These giants were nicknamed "Centennials" because the first unit, #6900, was completed in time for the 100th anniversary of the 1st Transcontinental RR. The DDA40Xs produced 6600HP with two EMD 645 prime movers. They were also test-beds for the new electrical systems that would find their way into EMD's Dash-2 locomotives, including their popular SD40-2. UP would use these big EMDs for high-speed freight services throughout the 1970s and 80s. Most were scrapped, but 13 of these monsters have survived in preservation. #6936 was operated with UP's Heritage Fleet until she was sold to the Railroad Heritage of Midwest America museum, where the giant diesel locomotive will be operated in museum service. 7.) EMD SD80MAC (Conrail #4100-4129): EMD in the 1990s was in a race with GE to build the most powerful diesel locomotive in the world. In 1995-96, EMD would produce their SD80MAC with a massive 20-Cylinder 710 prime mover that produced 5000HP. Conrail was the only buyer. The 30 units would later be split between CSX and NS, although NS eventually obtained all of the SD80MACs. They have all been scrapped, unfortunately. It's a pity that none were rebuilt as part of the NS and CPKC SD70ACU programs. 8.) EMD SD90MAC-H/SD90-43MAC: EMD's attempt to make a 6000HP diesel locomotive with one prime mover was not so successful. Their 4-stroke 265H engine (unlike the 567, 645, and 710 engines, which were all 2-stroke engines) was not very reliable, so only a few of the 6000HP units were built. They were designated SD90MAC-Hs. Only UP and CP ordered these monsters. Some were equipped with an upgraded nose that looked like an SD70ACe nose. These were the Phase II units. The 4300HP SD90-43MAC, with its 4300HP 710 prime mover, was far more successful than the 6000HP units. CP and UP have scrapped all of their 6000HP SD90s, while many of UP's 4300HP SD90 units have been rebuilt into SD70ACUs by NS and CP. UP still rosters some of the SD90-43MACs that weren't sold. 9.) GE AC6000CW: GE had some success with their own 6000HP monster, the AC6000CW. These beasts did have some issues, though, and most of them were built as "convertables" with 4400HP 7FDL-16 prime movers instead of the 6000HP 7HDL-16 engine. GE teamed up with the German Deutz-MWM Company to develop the 7HDL-16 6000HP engine. Only CSX, UP, and BHP Bilton (for iron ore service) in Western Australia ordered the 6000HP AC6000CW. UP ordered the convertable units, as well as the 6000HP units. UP's convertable units were designated C4460ACs. CSX rebuilt their CW60ACs with GEVO-16 prime movers (calling them ES46AHs; these produced 5800HP, but CSX rated them at 4600HP) before recently selling all of their units except for their 3 prototypes. UP has rebuilt all of their AC6000CWs with upgraded electrical systems and 7FDL-16s and designates the rebuilds as C44ACMs. A couple of these locos have been preserved. BHP scrapped their AC6000CW units after they couldn't find a buyer. Interesting fact: all 8 of the BHP AC6000CWs were used to pull the longest and heaviest train in the world. That world record still stands as of 2023. The iron ore train, with 682 loaded ore cars was over 4 miles long and weighed 109,938 US tons! This would make for a great scenario for an Aussie BHP Bilton Iron Ore Route (that should be made, by the way). 10.) Other big, powerful diesel loco ideas: -Progress Rail/EMD SD70ACe-T4: Tier 4-compliant SD70-series locomotive rated at 4600HP; these use a 12-cylinder 1010J prime mover that is based on the SD90's 265H. These beasts are not so reliable, but UP does roster 100 of them. The rest are PR/EMD lease units and the 10 former CSX units. -EMD SD45X: a 4200HP experimental loco with a 20-Cylinder 645 prime mover (basically a hot-rodded SD45) built to test Dash-2 electrical systems and other new tech by EMD. SP rostered 6 of these units in the 1970s, but they were not too reliable and were scrapped. -Chinese HXN5 (GE ES59ACi): China rosters 300 of these big 6250HP GEs that use the GEVO-16 Prime Mover. These locos would be the perfect mainline power for a future Chinese heavy freight route. -Chinese HXN3 (EMD JT56ACe): Another 6000HP (actually 6300HP) Chinese diesel, these use EMD's 265H engine which is the same engine as EMD's SD90MAC-H. China owns 334 of these big EMDs. Again, these could be used for heavy freight on a Chinese route.
