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Re: [BRHSlist] Digest Number 1870

To: BRHSlist@yahoogroups.com
Subject: Re: [BRHSlist] Digest Number 1870
From: William Barber <clipperw@EarthLink.net>
Date: Sun, 9 Nov 2003 11:46:05 -0600
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Jan,

EMD diesel engines in good running order shouldn't smoke. However, if 
they have been sitting around idling for a long time, they will emit 
blue colored smoke as they initially get under way, such as departing 
from Union Station in Chicago. Blue smoke indicates that unburned fuel 
has accumulated in the exhaust system. Once underway, the exhaust 
should be clear (just heat waves) or have a VERY slight haze. Black 
smoke from a diesel engine indicates a lack of sufficient combustion 
air. With four cycle engines (Alco, GE) this usually occurs as the 
engine is throttling up when the free wheeling (non gear train driven) 
turbocharger lags in speed due to insufficient exhaust gas flow. As the 
engine speeds up, exhaust gas flow increases and accelerates the turbo 
to the point that it meets the intake air requirements of the engine 
and the stack should clear. With 2 cycle EMD engines, black smoke 
usually indicated an air filtration problem. That is, the filters need 
to be changed.

On non turbocharged EMD engines (Roots blown which includes all of the 
E units) the blower speed increases in proportion with the engine speed 
and generally provides the appropriate air flow for each throttle 
position. On turbocharged EMD engines, the turbo is gear driven by a 
gear train from the crankshaft until it reaches the upper throttle 
positions (usually run 7 & 8, but on some engines even run 6). At that 
point, the exhaust gas flow has reached a sufficient volume to cause 
the turbo to free wheel up to speeds in the range of 18,000 rpm. The 
turbo has a built in overriding clutch to allow it to disengage from 
the gear train. When the engine is throttled down, the clutch reengages 
around run 7 or 6.

As noted earlier, except for engines that have been sitting around at 
idle for long periods, the stacks on a properly running engine should 
be essentially clear (no visible smoke). Unfortunately, our favorite 
RR, had a practice of doing everything for themselves in the way of 
repair. This included rebuild of fuel injectors. They also had a 
practice of salvaging as many parts a possible. While economical in one 
sense, it did not always result in the best rebuild of some components, 
including injectors. Thus, rebuilt Q injectors did not always operate 
properly "out of the box" and caused more smoke (and wasted fuel), but 
in an era (40's, 50's and 60's) when pollution was not a major concern 
and diesel fuel cost 9 cent per gallon, who cared? So, they saved money 
in rebuild.

In the last 20 years, fuel consumption and pollution have become major 
concerns. The Federal government through the EPA mandates emissions and 
the economy mandates fuel costs. Both builders have worked very hard to 
improve the performance of their engines in the recent years to improve 
fuel consumption and to meet EPA requirements. For instance, an SD40-2 
burns about 5 gallons per hour at idle while an SD70M burns about 2.5 
gal/hr. And at full load, the same SD40-2 burns about the same amount 
of fuel to produce 3000 h.p as an SD70M does to produce 4000 h.p.

Bill Barber

On Sunday, November 9, 2003, at 07:02 AM, BRHSlist@yahoogroups.com 
wrote:

>    Date: Sat, 8 Nov 2003 13:55:14 -0500
>    From: "Jan Kohl" <jkohl@nc.rr.com>
> Subject: Re: Broadway Limited CB&Q E7A initial thoughts (& spare!!)
>
>> Now what would be even better is if the sound systems (steam too) 
>> would be
>> sold separately and could be added to existing engines for use on 
>> annalog
>> layouts. That's what I would like to see.
>
>
> Now what I want to see is more locomotives with a decent smoke system.
> Talk about cool...blasting the horn on the E7 at full throttle with 
> black smoke
> billowing out as you pull out of the station.
>
> I can't think of a better way to annoy my family...   :)
>
> Cheers!
>
> Jan


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