710 Tier 2 Mods

[NOHAB-GM]

Does anyone know what the technical modifications to the 710 primemover or its systems constitutes, in order to make it Tier 2 compliant? Hardware or software changes, or both? EMD writes on their homepage that "...meeting Tier 2 emissions standards without adding any new technologies or complicated equipment to the 710 engine..."

Oeyvind

[tate955]

I think they acheive Tier 2 via extra cooling capacityand a few minor fueling tweaks. Some are sceptical that it is possible to lower the Nox on the 710 to Tier 2 by this method alone . Cynics!

[nickleinonen]

I think they acheive Tier 2 via extra cooling capacity and a few minor fueling tweaks.

i think the cooling system also gets split, with the right pump feeding the engine cooling system, and the left pump feeding water to the aftercoolers. i have seen the pumps on some UP units, and that new large main pump is almost as big, if not the same size as a cooling water pump on the ge fdl engines... not going to be picking that one up by hand to slip it into place...

[QuietGuy]

The separate aftercooling systems have been around for over ten years.

However, the modifications for the Tier 2 are more than "just hardware and software". There are several structural changes that preclude Tier 1 and previous engines from being modified into Tier 2. That is not to say that they could not be modified to meet Tier 2 emission standards, but they can not be modified to be identical to new Tier 2 engines. The amazing thing is that the new Tier 2 engines meet the emission standards without serious efficiency hits. The "dirty, fuel wasting" two-cycle is just as clean and within 2% of the GE Evo engine BSFC (brake specific fuel consumption). I heard rumors that GE promised money back if the GEVO's weren't X% better than the EMD's in fuel consumption, so the railroads took GE up on that and sent one of each to SWR for comparison tests. The GE's didn't do as promised - the EMD's did better than promised, so there was an exchange of funds.

I also heard that EMD has already had experimental engines meeting better than proposed Tier 3 standards without that big of a hit to efficiency, but they haven't decided whether to invest in the cost to bring it to the locomotive.

The problem with meeting the emission standards is that the NOx (nitrous oxides) must be reduced. The laws of thermodynamics state that the higher the temperature difference between the hot and cold sides of a work process, the higher the efficiency. Since the low temperature is ambient air, the higher efficiency comes from higher combustion temperatures in the chamber. But at higher temperatures, the nitrogen in the air (79% of the volume) begins to burn with the oxygen. This actually helps the process since it adds heat to the combustion. Most of the modifications to reduce the emissions of NOx shorten the burn process or lower the temperature. The 2-cycle has built in exhaust gas recirculation, an advantage over the 4-cycle. The Tier 2 EMD engine has a lot of cooling, combustion process modifications, and timing issues to reduce NOx without losing efficiency.

[trainiac]

The amazing thing is that the new Tier 2 engines meet the emission standards without serious efficiency hits. The "dirty, fuel wasting" two-cycle is just as clean and within 2% of the GE Evo engine BSFC (brake specific fuel consumption).

That coincides with a bit of research I did a while back, in which I found out that the 710 in an SD75 has a slighlty lower BSFC than the FDL in a Dash-9. Talk about contrary to popular belief (I was a little surprised, too)

[Nasadowsk]

<i>I also heard that EMD has already had experimental engines meeting better than proposed Tier 3 standards without that big of a hit to efficiency, but they haven't decided whether to invest in the cost to bring it to the locomotive.</i>

GE probbably does too.

It's not that the 2 stroke cycle is bad on fuel, it just SUCKS on hydrocarbon emissions because of the ports at the bottom of cylinder. It's unavoidable. As HC emissions tighten up, you'll see a bigger squeeze on the classic EMD design. But that doesn't mean they can't do a totally valve in head 2 stroke, though such a beast may/maynot be worthwhile.

The big gains are gonna be injector tech, injector control, and combustion chamber design, plus EGR and eventually catalysts and particulate traps. Maybe SCR - it's showing up in ships now.

Ultra low sulphur fuel will be a big help here, too. The soon it hits the US,. the better - you may finally see diesel automobiles again (since cali, etc have effectively legislated them out of existance with current fuels)

[QuietGuy]

[quote]It's not that the 2 stroke cycle is bad on fuel, it just SUCKS on hydrocarbon emissions because of the ports at the bottom of cylinder. [/quote]

That is not correct - the EMD 2-cycle does not and never did have a HC emission problem - it's only problems were meeting NOx without a big BSFC (fuel economy) hit.

[Nasadowsk]

That explains all the oil on the roof of them, then.

It's not an HC problem now. When the EPA finally gets seriously about diesel loco emissions? It will be.

[junction tower]

Why should locomotives be held to the same standards as automobiles or heavy trucks? That's like saying an electric power plant should have the same emission standards as a home furnace. Considering the tiny number of locomotives in use compared to cars and trucks, and considering their vast superiority in efficiency, (One stack train could take a couple hundred trucks off the road) I think the current standards are much ado about nothing. I don't think in the big scheme of things, loco emissions are going to have any measurable effect one way or another in air quality. I also don't think there are too many EMD operators dumping a couple of hundred gallons of oil a month in each unit. At the cost of lube oil, that would get prohibitive real quick. I think it is a real credit to the 2 stroke design that they have gotten all the way to tier ll without actually making any monumental changes in the architecture of the power plant. Who knows what might be possible in the future? If effective after treatment of the exhaust is devised, it may not matter that a little oil goes out. People have been trying to bury the pushrod automobile engine for 20 years, yet GM has shown that they can get tremendous power and efficiency in a lower cost, highly reliable powerplant. (A new Corvette pumps out 400 HP, makes 28 MPG, and is so clean, GM was able to remove some of the emissions equipment that was used on 2004 models. All with a 6 liter pushrod motor. I wouldn't write the 710's epitaph just yet. As for the 2 stroke Detroit Diesel, I don't know how much serious emission releated work was ever done to that engine. Detroit decided to go with a modern four stroke design before pollution controls even became a factor in the heavy truck market. I think the decision to dump the 2 strokes was based on the fact that customers had turned against it in the marketplace. They are finicky oil leakers, most are V engines which were never real popular in the diesel market, and the 92 series in particular had some terrible reliabilty problems. I know of a huge truck fleet in my home town that actually got one spare engine for every so many 92 series equipped trucks they bought. That doesn't do much to inspire confidence.

[QuietGuy]

I only have one other thing to say about emission standards. There is a way they are measured and calculated that has been established by the EPA. This has nothing to do with maintenance of the unit, or if it has been sitting idling for 3 days and "souping up". The EPA also establishes a way to measure mileage standards for automobiles, but this does not have anything to do with the actual mileage you may get with your car. The same holds true with the way locomotive emissions are measured and established. Have any of you ever witnessed a locomotive emission test?