Re: GE Turbo vs. EMD

Dennis Lippert <denlippert@...>

On Nov 27, 2008, at 5:42 PM, wrote:

*suspect information ahead - season to taste*

It seems that the EMD turbo is spun by the crankshaft at low RPMs to
provide additional air. When the exhaust speeds are high enough the
turbo freewheels via a clutch system so the EMD turbo is always "on".

The GE turbo is not geared in any way. When it notches up, you have
the lag on the turbo, so you get smoke until the turbo catches up at
higher RPMs. Hence, no turbo spin/noise at lower RPMs. At the usual
trackside vantages you get a lot of LUGLUGLUG noise, but no whine. If
you catch them on a grade or in heavy pulling you get the lugging and
the turbo whine.

Can anyone confirm this???
Yep. That is exactly the case. The EMD's two-stroke diesel requires
forced induction to feed the air into the cylinders... hence even the
earliest examples had Roots blowers on them.

EMD's turbo-supercharger is indeed designed (somehow) to freewheel
ahead of the crankshaft-driven speed once sufficient exhaust volume
is present to do so.

Now... that explains why you hear the turbo more of the TIME on an
EMD... but it doesn't explain why GE's turbo is not a dominant sound
feature. In fact, I never really associated the turbo sound with GE's at


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