ES44AC is more fuel efficient than SD70ACe

The results of an independent head-to-head fuel test between GE’s Evolution ES44AC and EMD’s SD70ACe Tier 2 emissions-compliant locomotives found that GE’s locomotives are more than 6% more fuel-efficient compared to their EMD counterparts.

Read more at:

http://www.greencarcongress.com/2009/06 ... 90618.html

There are some questions a few acquaintances of mine have:

o Was this a lab dynamometer test, or was this an actual over-the-road test?

o Which laboratory performed the tests?

Original press release from the GE website may be found here.

Im surprised its only 6% more fuel efficent, considering that EVO is a 12 Cylinder and the SD70 is a 16 cylinder

The GEVO cylinders are larger than the 710 cylinders. The overall displacement of the GEVO-12 is 188.4 liters, compared to 185.6 liters for the 16-710... so the GEVO-12 is actually a larger engine than the 16-710, in terms of overall displacement. That makes the 6% fuel efficiency advantage even more impressive.

This past weekend, I had the opportunity to chat with an individual with substantial engineering expertise with both GE and EMD.

This individual was, I think, properly skeptical of GE's claims. He went on to recite a number of areas where "fudge factors" -- computer settings, for example -- could be applied to skew numbers in favor of one side or the other. Until GE's report is available for public vetting, I will have to regard the GE claims with the same skepticism my acquaintance displayed.

In the words of the Russian proverb quoted by President Reagan, "Trust but verify."

Good points... and while a 6% fuel savings would be significant to a large railroad, it does seem like 6% could be within the margin of various factors that could effect fuel economy either positively or negatively over the course of the locomotive's average daily routine, including the very significant variable created by different train handling techniques employed by different locomotive engineers. In other words, an ES44AC on ABC Railroad operated today by Engineer Smith might be 6% more fuel efficient than an SD70ACe, while an identical ES44AC on XYZ Railroad operated tomorrow by Engineer Jones might be 6% less fuel efficient than an SD70ACe, owing to XYZ's different terrain and Jones' more aggressive train handling.

However, it does stand to reason that the GEVO-12 is somewhat more likely to be more fuel efficient than the 16-710, due to being a newer design and due to the amazing amount of resources that GE has invested in its development. But I agree that it would be really, really nice to see this report and see what the experts (who are not on GE's payroll) have to say about it.

I'm actually surprised the difference is that large, and while I wouldn't be surprised if the GEVO has an edge, I'm skeptical.

Figures I had come across back in 2005 (in a couple of emission tests in Canada and the US) put the 4000 and 4300 hp EMD 710 marginally ahead (1-3%) of the 4400 hp GE FDL in terms of brake specific fuel consumption. I recall GE press releases claiming that the GEVO engine was about 3% more efficient than the FDL. Assuming all of this is accurate, it would put the 710 and GEVO at about the same level of efficiency, with a bit of an edge to the GEVO. Since the 710 produces less horsepower, it would consume less fuel than the GEVO on a gallon-per-hour basis.

I think the idea of EMD units being fuel hogs is a holdover from an earlier era. Likely in response to higher fuel costs and competition from GE, EMD made tremendous advances in fuel efficiency between the 645 of the SD40 and the 710 of the SD70 series. As for the Roots-blown 645 of the GP38, it's a whopping 30% (or so) less efficient than the present 710. In other words, while GE locomotives were substantially more fuel-efficient than equivalent EMD units in the 1970s, there is no longer a significant difference.

An EPA report has surfaced comparing the latest GE and EMD locomotives. The title is "Particulate matter from Tier 2 locomotives." Its dated Jan.3, 2008 not Jan 2009. The test was run by Southwest Research Institute in San Antonio, TX. SWRI has developed many of the testing methods used by engine manufacturers for emission development projects. So you can't argue with their results. This test was for testing the results on both type of locomotives using the same batch of ultra low sulfur fuel for both locomotives. On page 4 they present the results for emissions. Interestingly both locomotives pass Tier 3 requirements., Of interest here is that it gives the BSFC (Brake Specific Fuel Consumption). 0.370 lbm/hp-hr for the GE and 0.372 lbm/hp-hr for the EMD. That's point 6% more efficient, if you round up from.54% or about one half of one percent. An insignificant difference. For the EMD to be 6% less efficient the bsfc would have to be 0.392. If you take 5 EMD's and tested them you would probably get a wider variation- probably 2 to 3%. GE plays fast and loose with the data so I still think they are set up to lose more bets.

RickRackstop wrote:An EPA report has surfaced comparing the latest GE and EMD locomotives. The title is "Particulate matter from Tier 2 locomotives." Its dated Jan.3, 2008 not Jan 2009. The test was run by Southwest Research Institute in San Antonio, TX. SWRI has developed many of the testing methods used by engine manufacturers for emission development projects. So you can't argue with their results. This test was for testing the results on both type of locomotives using the same batch of ultra low sulfur fuel for both locomotives. On page 4 they present the results for emissions. Interestingly both locomotives pass Tier 3 requirements., Of interest here is that it gives the BSFC (Brake Specific Fuel Consumption). 0.370 lbm/hp-hr for the GE and 0.372 lbm/hp-hr for the EMD. That's point 6% more efficient, if you round up from.54% or about one half of one percent. An insignificant difference. For the EMD to be 6% less efficient the bsfc would have to be 0.392. If you take 5 EMD's and tested them you would probably get a wider variation- probably 2 to 3%. GE plays fast and loose with the data so I still think they are set up to lose more bets.

Sorry, but what is lbm/hp-hr in metric units? I understand hp-hr, but lbm?

I can not find those units in
http://www.infoom.se/omvandla-konverter ... a_vikt.htm

lbm is pounds mass or just use .370 pounds per horsepower hour. One thing that should be mentioned ias that both locomotives were tested on the self loading procedure so the raw reading was kilowatts from the alternator. The purpose of the test was to get emissions data on a batch of ultra low sulfur fuel.

bengtSorry wrote: but what is lbm/hp-hr in metric units? I understand hp-hr, but lbm?

I can not find those units in
http://www.infoom.se/omvandla-konverter ... a_vikt.htm

lbm means Pounds or Pounds Mass. It can also be listed as lb.

Brake Specific Fuel Consumption (BSFC)
BSFC is a measure of engine efficiency. It is the ratio of the engine fuel consumption to the engine power output as measured at the flywheel. BSFC has units of grams of fuel per kilowatt-hour (g/kWh) or pounds mass of fuel per horsepower-hour (lb/hp-hr).

The conversion between metric and U.S. units is:

BSFC_METRIC(g/kWh) = BSFC_US(Lbs/(HP*Hr)) * 608.277
BSFC_US(Lbs/(HP*Hr)) = BSFC_METRIC(g/kWh) * 0.001644

Some of the efficiencies occur between the prime mover and the rails. For instance, the new ES44C4 is even more efficient than the standard Evo locomotive yet it retains the exact same prime mover. So by comparing the prime mover BSFC, that will not really tell you the fuel efficency of the locomotive as that refers only to the fuel useage to get a specific hp value at the crankshaft, not the power to the rails.

GE basis their bragging rights purely on the BSFC figure. The only thing to look at for marine propulsion or generator set.

There are SO many variables in railroading that it's almost impossible to determine the true fuel efficiency of a locomotive. The Santa Fe did tests that showed that the SD45 is actually more fuel efficient than the SD40, yet other railroads thought otherwise. One mans ES44AC may be operating under different conditions than another mans. To accurately compare the fuel efficiency of the ES44AC and the SD70ACe, you'd have to get THOUSANDS of locomotives, account for every possible variable, and average the data. Frankly, that would be far to expensive, so companies will often limit their studies to smaller scales, which leads to less accurate data. An ES44AC on flat terrain like the Golden State Route will do far better when it comes to fuel efficiency than an SD70ACe on the Moffat Route.

The purpose of the test was to eliminate the variables, that is they read the generator output on self test with a sample of ultra low sulfur fuel with Southwest Researches' own fuel measuring equipment that carefully maintains the fuel temperature.