>Do you know what the amperage rating or pounds retarding force the dynamics create? Are they comparable to a GP7 or less?

Dynamic brake effort is a function of the traction motor characteristics and engine weight (on drivers). The 1127 is approximately the weight of a GP7/GP9, and the traction motors are the same (traction motor cooling air ducting is different). In dynamic, all you can do is regulate the current generated, not the voltage, and the max current for dynamics is around 750. So the retarding capabilities are approximately the same. I've run the 1127 on the SP several times. The first time, the dynamics hadn't been turned off, and it's a little disconcerting to have that fan turning so fast right in front of the windshield. The next few times I ran it, the dynamics had been turned off (most of these cow units had already had this done). Where the 1127 is "smaller" is in pulling power and speed because the diesel engine has fewer cylinders.