There is something wrong if you have to wrench in that much voltage just to get the locomotive to move...especially if it is not trailing any 'tonnage'.
As the previous poster says, CV2 is usually the CV that you must adjust in order to get the start voltage up to where the loco just begins to turn its wheels when you dial in the very first speed step on your throttle. Each engine is different, but values in modern engines much above 45 are rare. You may get some serious heat buildup under that shell if it takes a lot of voltage to get the loco to move around at 30-40 scale mph. So, you may have to remove the shell and inspect the drive components for unwanted friction from wires, metal tabs, dry gears, dry axles, or a pinched-whatever.....they all add up.
Sometimes a full factory restore of your defaults settings is the best cure. Do a factory reset.
The 'culprit' on your layout could be you! If you have any rail components twisted so that they are not fully level, especially on a curve, and doubly especially on a curved approach to a hill, including the vertical curve that transitions to the grade, you will find six axle diesels very unforgiving. The rails heights must be the same, and their long axis must be very close to the same, except that they can bend very slightly and change over maybe 12-15". If it is too abrupt, your longer six axle trucks will lift a wheel enough that the flange will not guide the truck properly, and the result is what you are seeing.
You need to take a rigid and light straightedge and place it on top of the rails all along the approaches to the affected area. Get down and look at it with your eyes level with the rail tops. Look for light that should not be between the straightedge and the rail tops. Some is fine, especially if it is a shallow curve over 8" or more, but if you have a good visible dip, or a hump, you have problems. Look for the cure to be somewhere about 6" before the derailment, maybe more. Sometimes what is happening to the rear truck is what horses the loco frame up enough to cause the front truck to derail.
You need to be patient, observant, use good light, and do many trials to figure out what is happening. Usually it is a humped or dipped rail somewhere. It only takes about 1/2 a mm for this to happen...I know because I have had to soften ballast with water and then pry up tracks just a bit, shim under them, and then wait for the ballast to dry and harden once more. That works, but finding out where to do this can be a test.
BEMF doesn't work all that well on our models as a brake. It is way better than with AC current on O guage models, or so I have heard, but it isn't something you should count on with heavy trains trying to shove the engine down grade. Instead, it works better as an inducement to the motor to accelerate just sufficiently as the voltage rises from the throttle settings. It also keeps the motor within a narrow spinning rate when it experiences a sudden shift in load. It makes the engine work harder if on a grade, for example. Maybe some of this effect will help to retard the locomotive's speed down a grade, but I wouldn't count on it.
-Crandell
