Randy Stahl wrote: oltmannd wrote: wildrails wrote: No, I'm comparing roots 645 with roots 567 (both naturally aspirated) here is the sound I'm talking about:http://www.yardoffice.com/RR/DieselSounds/Track15Sample.mp3 I've never heard a roots NA 645 load-up like that, it never sounds so "pulsating" I guess you could sort it under nuances, but what makes the difference? Sounds like somebody needs to check the rack settings on the injectors.......Sounds right to me , Sounds just like a SW1500 !!!!! that is a 12 cyl 645. The GP 38 sounds a little tougher , with a 16 cyl , it ought to !!
oltmannd wrote: wildrails wrote: No, I'm comparing roots 645 with roots 567 (both naturally aspirated) here is the sound I'm talking about:http://www.yardoffice.com/RR/DieselSounds/Track15Sample.mp3 I've never heard a roots NA 645 load-up like that, it never sounds so "pulsating" I guess you could sort it under nuances, but what makes the difference? Sounds like somebody needs to check the rack settings on the injectors.......
wildrails wrote: No, I'm comparing roots 645 with roots 567 (both naturally aspirated) here is the sound I'm talking about:http://www.yardoffice.com/RR/DieselSounds/Track15Sample.mp3 I've never heard a roots NA 645 load-up like that, it never sounds so "pulsating" I guess you could sort it under nuances, but what makes the difference?
No, I'm comparing roots 645 with roots 567 (both naturally aspirated)
here is the sound I'm talking about:
I've never heard a roots NA 645 load-up like that, it never sounds so "pulsating"
I guess you could sort it under nuances, but what makes the difference?
Sounds like somebody needs to check the rack settings on the injectors.......
Sounds right to me , Sounds just like a SW1500 !!!!! that is a 12 cyl 645. The GP 38 sounds a little tougher , with a 16 cyl , it ought to !!
Just imagine what this sounded like! 3 of 'em, loaded train, plus uphill!
Dan
Sorry about that, I thought the supercharger compresses air in cars. Don't know much about car engines.
Technically, a 'Roots blower' is a supercharger. Even on high performance cars with Roots blowers, the air is not compressed into the engine as a Roots blower cannot compress air. It pumps air.
Although the Roots blower approach is considered to be, "Naturally aspirated" is not a correct term for the EMD 2-stroke engine, as this engine design simply will not run in a conventionally naturally aspirated configuration. Hence the Roots blower or turbo unit.
Natural aspiration in the strict sense is the engine breathing on its own, without help.
A supercharger fills the cylinder with compressed air. The roots blower fills the cylinder with near-atmosphere pressure air. It only serves as a "ventilator" that fills the cylinder with air because there is no intake stroke.
Of course, the principle is the same, it's just a difference of how you set the compressor device, will it compress air , or just exchange it
So in principle, a roots blower can serve as a supercharger, but in this case doesn't
There is only a small pressure difference to stop exhaust gasses from returning to the cylinder, but that pressure difference is not enough to be considered "supercharged".
someone correct me if I'm wrong
But I'm still currious about this rack setting. I suspect Don ment the rack that rotates the gears of individual pumps that control the amount of fuel that is being injected. If that is so, I'm not sure what could this mean, that one of the gears skips a tooth and provides more fuel to one of the cylinders than the rest?? Is that what makes the chugging sound (one cylinder firing stronger)?
Jock Ellis Cumming, GA US of A Georgia Association of Railroad Passengers
Now you've got me REALLY currious...
can you please explain that last comment?
You mean, this is not how a 567 normally would sound? What do you mean by rack setting?
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Could it be notch 8 engine speed? Most 645E engines run at 900 RPM in notch 8. 567B and below run at 800 RPM and 567C at 835 RPM.
I could always tell the difference between a 12-645E powered MP15 and a 16-567C SD9 by sound, but the difference was due mostly to the whine of the TM blowers on the SD9 rather than engine sound.
First is coming from a GP7, and the other one is coming from an export G26CW, which is like an SD unit with 4 stacks. First is a 567 engine, the second is a 645
Well, yea, the difference could be in the exhaust and not so much in the engine, but I'm still currious what that difference is
Well I'm not the first person to report that a 567 has a "chug", like a helicopter.
I've heard so many folks say that, that I considered it a kind of a "trademark" of 567 engines...
Here is a 16-645E for comparison. Now I can't say anything about realism of the first recording, but this one I made myself, and can tell you for sure that this is how it sounded, if you use headphones that is.
http://free-os.t-com.hr/redmist/2062kretanje.mp3
Notice how, when this one loads-up, it has a very different exhaust texture. You mentioned the word "barking", that's a good word, but I'd use it in reverse, I'd say the 567 barks in the first recording, while you can't hear the barking in this recording of 645. It's more of a crunchy sound that the exhaust of this 645 makes.
Hmm, well, I wasn't there and I have no way of knowing if the recording is a true and accurate representation of the real sound especially as it comes out of my computer speakers. To me, it doesn't sound any different than any Roots-blown 645, and if you had told me it was a 567, I would have assumed it was that too. 645s do have a little more "bark" to them but it's not a large difference.
I used to fix these things so I'm very familiar with their sound.
Beats me why one engine design sounds different than another. I am aware of differences in bore, stroke, manifold, number of cylinders, etc., and I can even draw correlations. In the field I can from experience tell without looking whether I'm listening to a 16-567C, 16-645C, or 16-645E, but how those differences cause the sound difference I do not know, and I don't wish to guess.
S. Hadid
wildrails wrote:Hi When comparing roots blown 567 and 645 engines, I've noticed that 567 engine has a certain "chugging" sound, that 645 lacks. It seems to me like 645 engines have a much smoother sounding exhaust, while 567 have this periodical pounding, or a very distinghuished exhaust note. I'm sure anyone who has ever heard a 567 engine, knows what I'm talking about But I'm confused , because, I though there isn't that much difference between these engines, exept for larger bore diameter (even the stroke is the same) and that it is even possible to convert 567 to 645 So, does anyone have any idea what makes the difference in sound? Why does a 567 go chug-chug-chug-chug under load, while a 645 goes more like a continuous thunder Is the sicret in exhaust manifolding? Or something else?
Hi
When comparing roots blown 567 and 645 engines, I've noticed that 567 engine has a certain "chugging" sound, that 645 lacks. It seems to me like 645 engines have a much smoother sounding exhaust, while 567 have this periodical pounding, or a very distinghuished exhaust note.
I'm sure anyone who has ever heard a 567 engine, knows what I'm talking about
But I'm confused , because, I though there isn't that much difference between these engines, exept for larger bore diameter (even the stroke is the same) and that it is even possible to convert 567 to 645
So, does anyone have any idea what makes the difference in sound? Why does a 567 go chug-chug-chug-chug under load, while a 645 goes more like a continuous thunder
Is the sicret in exhaust manifolding? Or something else?
I suspect you're listening to normally aspirated (Roots-blown) 567s and turbocharged 645s. There is not a large difference in sound between Roots-blown 567s and 645s, and turbocharged 567s and 645s. There ARE differences in sound but they are more in the category of nuances.
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