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Re: (erielack) ALCOS
Alcos have exhaust-driven turbochargers, so the turbo during rapid accelerations lags behind the respiratory demands of the prime mover, thus the inefficient combustion (smoke) when they first start moving.
EMD turbos are mechanically driven off of the prime mover ....Mike
- -----Original Message-----
From: paultup <paultup_@_comcast.net>
To: EL Mail List <erielack_@_lists.railfan.net>
Sent: Thu, Oct 11, 2012 12:50 pm
Subject: Re: (erielack) ALCOS
Ed Montgomery asked:
>Alco engines always seemed to accelerate with a blast of dark exhaust>coming out the stack. I remember hearing this was caused by the>turbocharger lagging. Could this have been corrected or was it part of the>engine design?
I've always wondered that myself. Alcos and GEs tend to have the black exhaustspurts common to turbo lag - and coincidentally, both use 4-cycle prime movers.
Notably, earlier Alcos (539 series prime movers) don't really show large blackclouds like this (think RS1 and S2/S4), which also puzzles me.
> Was it common to all ALCO engines?
It seems to happen most on 244 and 251 engines, notably the latter. I'm assumingEMD's turbo design had better free-flow in the turbo, which results in lessexhaust. This really would be a turbocharger issue rather than a prime moverproblem, IMHO. If Alco used a larger turbo with heavier blades, the inertia atthe start would be greater, allowing the initial exhaust burst to fly past theturbine blade before they were up to speed.
> I heard stories of fires breaking out around the exhaust stack of the PA's.Was this common> to the RS and S units as well?
I've never heard of those, but it could be because of the PA's carbody designand oil accumulation at the stack.
- - Paul
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