Tier 4 engines

[erikem]

FlightPlan - Welcome to the forum!

[FlightPlan]

The tier 4 GE are most certainly not louder than any other locomotive. In fact it is much quieter. I work for a major class 1 railroad and my shop sees these on a daily basis. I can walk around one at idle without hearing protection. Something I wouldn't even consider with anything else.

I Would guess the noise drop has a lot to do with the new fuel pumps and injectors. Also has to do with the two turbos and intercooler and  aftercooler setup.

I have seen it mentioned before, but all GE Tier 4 units do NOT have a DPF. Emissions was met with the new fuel system, dual turbos and EGR.

[YoHo1975]

I've yet to see one under full load, and in fact, most of them I've seen with a GEVO/AC4400/SD70 in consist, so the distinct sound is a bit lost. It low throttle notch they sound MOSTLY like a GEVO. Slightly different of course due to reasons already mentioned, but basically like an EVO GE.

[ROBERT M BRAEUNER]

For those that have seen the engines running under load, do they sound anything like an emd unit or because of the four cycle engine, is it unique? Sound similar to a GE unit?

[M636C]

In Australia, our twenty year old Cv40-9i units are getting new FDL engines with more modern electronic fuel injection but using the same mufflers and they make a different and louder sound, as do the more recent C44 aci units.

The noise regulations are really severe and you can often not hear a train with three units approaching on nearly level track.

However the tests are carried out stationary, with the power fed to the dynamic brakes, so while the dynamic brake fan has to meet the sound restrictions, the traction motors are never tested. The sound of a loco in dynamic brake is thus the loudest it gets from the whine of the motors.

M636C

[CPM500]

The fact that the Tier IV GEVO has two turbochargers in series attenuates the exhaust noise without requiring a silencer.

 

CPM500

 

 

[Wizlish]

CPM500

The Tier IV units have no silencer, so they are louder.

What I suspect is that the situation is more complex in detail.  I expect there are noise-emission guidelines that apply to these engines, so 'leaving the muffler off' (or the railroad equivalent of 'straight-piping') is probably not what was done.  Instead I suspect that the particulate filter and associated plumbing 'acts' as the muffler to attenuate some of the gas noise -- so what you hear will be the 'bands' of frequency that preferentially get through because this is designed for flow, not baffling as in a muffler.  Could it be that the timbre or the low-frequency components of the exhaust noise are present more preferentially, and/or the 'official' Government noise testing is done A-weighted at a particular distance and angle and misses how some of the noise is emitted?

[NorthWest]

Interesting and a bit surprising. Thanks!

[CPM500]

The Tier IV units have no silencer, so they are louder.

[M636C]

NorthWest

I have observed some on Cajon Pass. I didn't see any soot, but these are new engines so they probably have little engine wear that would cause smoking etc.

Strangely, they seemed a lot louder than the earlier GEs.

 

I don't think Tier 4 allows for "a little engine wear that would cause smoking".

 

Smoke is particulate matter that is limited under Tier 4 (and the other Tiers).      While they might emit some particulate after a period of service, it can only be the amount allowed under the emissions regulations. Im fairly certain that the locomotive has to continue to meet the whole of the Tier 4 standards for the whole of its life. This won't make overhauls cheaper.

 

M636C

[LensCapOn]

From the videos I've seen, there is no smoke or soot in the exhaust, but a shimmering heat wave is very visible. 

[NorthWest]

I have observed some on Cajon Pass. I didn't see any soot, but these are new engines so they probably have little engine wear that would cause smoking etc.

Strangely, they seemed a lot louder than the earlier GEs.

[YoHo1975]

UP has the Tier 4 Gevos assigned to Hinkle working the I5 corridor, so they are in Roseville pretty regularly. I've seen them idling in the yard and on inbound trains. I've seen the heat distortion out the stacks, but not much else. Of course as noted, even a Tier 3 unit in good repair has little visible exhaust beyond heat

[Entropy]

Pueblo and surrounding areas are used by many companies for high altitude testing which is less oxygen dense. Alamosa is 7500' above sea level. "Hot and High" are the most demanding conditions for equipment. For example turbochargers spin faster in thin air. Its a proving ground. 

[Mark80439]

I saw EMD's SD70ACe-T4 last weekend in Alamosa, Colorado. Any idea why this unit was there?

[Wizlish]

nyc#25

Is there any noticeable exhaust out of the stack?

I don't know directly yet, either, but this raises interesting questions.

"Visible" should never involve black smoke opacity, because the filter will catch it.  On the other hand, I do expect 'heat wiggles' in the exhaust, and if the DPF regeneration is anything like the system as used in trucks, perhaps visible flame.

I don't think any unburned fuel or oil mist (white smoke) would make it through the DPF, even if no reduction catalyst (which isn't needed for a properly-managed diesel engine anyway) were present to 'combust' it.  This in turn raises the question whether a Tier 4 engine is 'permitted' (by its computer) to run with even one power assembly misfiring, for example in the time-honored GE injector fashion... if not, expect some fun coming soon to UP and other power departments that have gotten used to dispatching power with non-powering cylinders ...

[nyc#25]

   I have yet to see a tier 4 locomotive in action.

Is there any noticible exhaust out of the stack?