90mac and ac6000

[Anonymous]

Noticed from other posts that the sd40-sd75 were preferred by road crews because of their quicker loading. Is this due to the emd's having 2 cycle engines verses GE's 4 cycles? This begs the question, how do the new 4 cycles engines from emd/ge compare on loading?

[Anonymous]

the difference isn't due to the cycles, it is entirely in the way the load regulators work on the 2 types. as far as engines themselves go, for example your car has a 4cycle motor, they both rev up pretty quickly. the primary reason that GE doesn't load up as quick is that GE doesn't want it to. among reasons GE doesn't want their's to load so quick is that the turbocharger on a GE is entirely driven by exhaust gases (EMD's is mechanically driven until notch 6) and if you load it before the turbo "catches up" you get a ton of smoke, (of course GE's are smokey anyway). also GE's wheelslip system works different than EMD's, and this restrict's their loading speed also. as for the AC6000's and 90MAC's they both have software in the computer that limits how quick they load, although the EMD is still quicker loading, it is not as fast as older EMD's, and the GE is somewhat faster than older GE's. as a little side note, when running the AC6000's, in the cab the engine has a very wierd sound, kind'of a howling or something, in throttles 2,3,4 and then it goes away. Still haven't figured out what is making that sound. the EMD's are so quiet with that isolated cab, you can hardly even hear the engine, unless the windows are open, but you do "feel" it, a real low throbbing sound, they sound powerful. hope some of this answers your question.

[PaulWWoodring]

I think I can shed some light on the howling sound that AC6000's make (I think it has a kind of sci-fi space ship quality to it). Anyway, it has to do with the inverter capacitors that change DC to AC current. I found this out when another engineer was showing me the capacitor room on one. There is a bar across the access door to the room that has to be moved up and out of the way to get inside. According to the instructional video on these units, if you didn't put the bar up you would DIE if you enter there. When the bar is moved from across the doorway, the capacitors unload and the whiring noise stops. So I guess that that is where the noise is coming from.

[Anonymous]

thanks, i could tell it was from that area, but hadn't been able to figure out the sound, i would have thought the capacitors would be silent, perhaps blowers or something. anyway that space ship sound is a good description. wonder why the AC4400's don't make the same noise?