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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