All that is required to change the rating is reprogramming the computer. This is possible with any modern locomotive.
$switch = var(hpswitchposition) if $switch = "4000" then goto #4000fuelcode else goto #4400fuelcode
Normal operations call for the switch to be left in 4400HP position. The loco will produce 4400HP in Notch 8 from 0.1MPH to 25MPH while accelerating, then automatically reduce to 4000HP at speeds above 25MPH. If the loco speed drops to 15MPH, then the loco will again produce 4400HP. This is deemed a fuel saving feature.