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[Anonymous]

A few years ago i was train waching by the small CSX yard in Bridgeport Alabama,.An EMD locomotive(i think it was an SD40)was ideling in front of the office and it sounded like every time the air compresser cycled that the prime mover throtteled up a notch.Did i imagine this or are some engines set up this way?

[Anonymous]

A few years ago i was train waching by the small CSX yard in Bridgeport Alabama,.An EMD locomotive(i think it was an SD40)was ideling in front of the office and it sounded like every time the air compresser cycled that the prime mover throtteled up a notch.Did i imagine this or are some engines set up this way?

[csxengineer98]

first of all.... csx EMD units have a shaft driven air compresser..so as long as the prime mover is running.... the air compresser is in opporation.... so that isnt the reason... now if it was in the winter... some power has some techo crap that when i do believe its the cooling water..falles below a preset temp setting...the engin reves up to warm the water up...now im not 100% about it in the summer..but it might be the same thing but in reverse.... the engin starts to get hot ideling..so it reves up to move more water to help cool it... i could be wrong on some of this..it has been some years since i was at hogg head high for CSX... some other hoggers might have some more or better info to give you..but i hope this is a good start
csx engineer

[csxengineer98]

first of all.... csx EMD units have a shaft driven air compresser..so as long as the prime mover is running.... the air compresser is in opporation.... so that isnt the reason... now if it was in the winter... some power has some techo crap that when i do believe its the cooling water..falles below a preset temp setting...the engin reves up to warm the water up...now im not 100% about it in the summer..but it might be the same thing but in reverse.... the engin starts to get hot ideling..so it reves up to move more water to help cool it... i could be wrong on some of this..it has been some years since i was at hogg head high for CSX... some other hoggers might have some more or better info to give you..but i hope this is a good start
csx engineer

[Anonymous]

Although the air compressors are direct driven from the prime mover, they are not always "pumping". when air is needed, the valves in the compressor close, and the pumping conitinues until the resevoir pressure is satisfyed, then they open again, and the pump just free-wheels along. I have heard some engines where there is no change in the engine rpm when the pump is on, and on some newer engines, it does seem to pick up a bit. I'm not sure if the pick up is an acutal "run" position, just a slight increase in rpm.

David Wallace

[Anonymous]

Although the air compressors are direct driven from the prime mover, they are not always "pumping". when air is needed, the valves in the compressor close, and the pumping conitinues until the resevoir pressure is satisfyed, then they open again, and the pump just free-wheels along. I have heard some engines where there is no change in the engine rpm when the pump is on, and on some newer engines, it does seem to pick up a bit. I'm not sure if the pick up is an acutal "run" position, just a slight increase in rpm.

David Wallace

[Anonymous]

Thanks for the replys.

[Anonymous]

Thanks for the replys.