Wondering after looking at the newest catalog, specifically the difference in the UP sd40-2, with the other RRs. It appears that it does not have the distinctive porch on the backside of the engine. Also the radiator fans in the rear are missing. Is this a mod specific to the UP? Thanks.
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Its an SD40T-2, also known as a Tunnel Motor. UP inherited these from SP.
Also the radiator fans in the rear are missing. Is this a mod specific to the UP?
The radiators/fans were moved to the bottom of the engine body at the rear. The radiator vent openings are down next to the walkways. This was done because heat/exhaust rising from the engines to the tops of tunnels caused overheating if the radiators were located on top of the engine, so they moved them down lower to catch cooler air. So came the name "tunnel motors." In addition to the SP, the Rio Grande used them, too (which UP also inherited). Apparently some modern technology has eliminated this problem in newer engines.
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