Fuel Efficiency of Freight Diesel locomotives, Tier 3 vs. Tier 4

[Anonymous]

From time to time the question arose in different threads if Tier 4 GE and EMD diesel-electric freight locomotives are more or less fuel efficient than their Tier 3 counterparts. I haven’t seen any data that proofs either answer. But I'm interested in answers.

Last time it came up in the thread:News Wire: CN orders 200 locomotives from GE

I think the fuel efficiency question might be overlooked in that thread. So I created this thread and copied all posts from the above mentioned into this post.

Xxxxxxxx  Poster and date of post

Italic: Quote from previous post

IIIIIIIII Poster of the quoted post

Posted by kgbw49 on Saturday, December 23, 2017 12:01 AM

For the engineering types out there, why do Tier 3 engines continue to be ordered? It seems like any chance they get, the railroads will order a Tier 3 unit rather than a Tier 4 unit. Are Tier 3 units less expensive up front? Or are they more fuel efficient? Or less maintenance-intensive? Please note I am not a proponent for more Tier 4 rather than Tier 3 or some such. I am just wanting to learn more. Thanks in advance for any insight you might be willing to share!

Posted by NorthWest on Saturday, December 23, 2017 12:18 AM

All three: they are cheaper to buy, cheaper to run and cheaper to maintain. They also are more fuel efficient.

Posted by VOLKER LANDWEHR on Saturday, December 23, 2017 10:03 AM

NorthWest
They also are more fuel efficient.

Do you have any fuel consumption that show this?

I tried to find informtion. In an EMD 710 brochure is a chart that the fuel consumption got better from Tier 1 to Tier 3: s7d2.scene7.com/is/content/Caterpillar/CM20170915-60253-59723

I didn't find a comparison of a EMD 710-T3 and a EMD 1010-T4.

The 1010-T4 is a newly designed four-stroke engine with a completely different auxilliary management, idle measures etc. It is not the engine alone it is the whole package that is relevant.

Canadian railroads can buy Tier 3 engines for use in Canada as they don't have the same emission regulation.
Regards, Volker

Posted by caldreamer on Saturday, December 23, 2017 2:19 PM
I do not beleive that tier 3 locomotives are more fuel efficent than tier 4's untill I see the actual fuel use per hour for each notch setting for both engines.

Posted by Overmod on Saturday, December 23, 2017 2:44 PM
caldreamer
I do not believe that tier 3 locomotives are more fuel efficient than tier 4's untill I see the actual fuel use per hour for each notch setting for both engines.

That would be wise; I'm surprised that someone like Volker hasn't taken the time yet to compile the data in one place.

The GM two-stroke engine is inherently less fuel-efficient than an engine with a four-stroke cycle, for a number of reasons we've discussed in different threads.  This was brought up in at least two of the discussions on the 265-H engine (whether or not you subscribe to the "1010 evolved out of the 265 design", the 1010 has the same relative combustion efficiency over the 710 family)

One point that needs to be carefully considered is that a Tier 4 design that uses SCR can intentionally use hotter/better combustion in its power stroke, and compensate fully for the additional NO generation by increasing the consumption of the ammonia source if necessary.  This is a reason for the push towards 'liquids consumption' rather than just specific fuel consumption in determining a fair measure of 'fuel use' economically.

Now, I believe the existing 'practical' (meaning 'those railroads will buy') Tier 4 freight locomotives are still relying on relatively carefully-managed EGR to meet standards; that argues to me that even before discussing a need for active 'particulate filter regeneration' the actual sfc will be at least slightly higher for the same engine output provided by an equivalent Tier 3 compliant unit.  But I will wait for detailed data.

Posted by VOLKER LANDWEHR on Saturday, December 23, 2017 4:13 PM

Overmod
That would be wise; I'm surprised someone like Volker hasn't taken the time yet to compile the data in one place.

I would have if had more data than linked above. That is the reason I asked. So someone else hopefully does the legwork.

I doubt myself that freight Tier 4 locomotives are less fuel efficient. That the EGR equipped Tier 4 locomotives don't need diesel particulate filters shows that they have a completer combustion needing less fuel for the same output.
Regards, Volker

Edit: Perhaps we should create a separate thread. Here it might get lost.

Posted by NorthWest on Saturday, December 23, 2017 5:30 PM

I have no information on the EMDs, and as the prime mover is different I should have restricted my comments to the GEs. EGR has traditionally reduced fuel economy somewhat (ballpark <10%) between otherwise similar model runs. I don't know if that is the case here, but I suspect the efforts to reduce NOx output without SCR have reduced fuel efficiency.

Posted by Overmod on Sunday, December 24, 2017 4:28 PM

VOLKER LANDWEHR
Edit: Perhaps we should create a separate thread. Here it might get lost.

I concur ... do it!

We can then recapitulate the physics and engineering briefly there so the discussion stays on proper tech focus.

Posted by kgbw49 on Sunday, December 24, 2017 4:51 PM

I am glad I asked the question! And thank you all for the excellent information - I have learned a lot already! Much appreciated!

Posted by samfp1943 on Monday, December 25, 2017 3:12 AM

VOLKER LANDWEHR
I  would have if had more data than linked above. That is the reason I asked. So someone else hopefully does the legwork.

I doubt myself that freight Tier 4 locomotives are less fuel efficient. That the EGR equipped Tier 4 locomotives don't need diesel particulate filters shows that they have a completer combustion needing less fuel for the same output.
Regards, Volker

Edit: Perhaps we should create a separate thread. Here it might get lost.

Overmod
That would be wise; I'm surprised someone like Volker hasn't taken the time yet to compile the data in one place. 

 A short SEARCH of "Fuel Consumption on General Electric Tier 4 Locomotives?"  Turned up the following linked site:

@  https://www.csx.com/index.cfm/about-us/the-csx-advantage/fuel-efficiency/?mobileFormat=true

This is information from a CSX Document titled: "Fuel Efficiency"  .

A further Search on "EMD Tier 4 Locomotive performance" turned up a number of sites, but this linked "Railway Age " seemed to offer some information(?)

Linked @  http://www.railwayage.com/index.php/mechanical/locomotives/engines-of-change.html

FTA:"...• EMD’s Tier 4 freight locomotive, the SD70ACe-T4, is powered by an all-new, 4,400-traction-hp, 12-cylinder, four-stroke EMD-developed 1010 diesel engine. EMD attained Tier 4 without the use of urea as an after-treatment. The 1010 is a radical departure from EMD’s traditional two-stroke engine. It is not based on a Caterpillar engine, though, according to Progress Rail President and CEO Billy Ainsworth, it “combines the engineering expertise of Progress Rail, Electro-Motive and Caterpillar.” EMD’s other Tier 4 offering, the F125 Spirit high-speed passenger locomotive, utilizes a 4,700-hp Caterpillar C175-20 engine..."

Hope this will shed some light on this topic!

Sam

I hope I got it right and didn't forget something important.
I look for input from people who might have overlooked the other thread.

Regards, Volker

[Overmod]

Highly amusing in that Railway Age story to watch Ainsworth and his minions try as hard as they can to avoid having to say anything containing the number "265" or the letter "H" by itself.

Someone might want to link some of the previous discussion about why a 4-stroke compression-ignition engine was inherently more fuel-efficient than a GM 2-stroke, and list the reasons why the difference can be less pronounced (but probably still present in typical locomotive uses).  I would prefer that someone else lead off because I will forget or miss something important.  Proportional pilot injection using EFI is an important consideration.

[nfotis]

Hello there,

 

one way to get the fuel consumption is to look for BSFC (brake-specific fuel consumption, I think). This number is variable with engine speed (RPM), and it is often expressed as grams per kW-hr

I have seen a diagram about the C175-16 where BSFC plays between 225 and 205 grams, at full throttle is consuming 210 grams for a total output of 2.8 MW.

The 20V R4000 43L from MTU has the same BSFC as the C175-16, giving 3 MW power output, while the 12V model consumes 207 grams for 2.4 MW.

The EMD 710G-16 has been referenced at 203 grams for 3.2 MW (yes, this is lower fuel consumption than the 4-stroke engines above)

 

N.F.

 

 

[erikem]

FWIW, 225g/kwhr is equivalent to 0.370lb/hp-hr, 203g/kwhr is equivalent to 0.334 lb/hp-hr.

I vaguely recall the C175-16 as running at a significantly higher speed than the 710G-16, which may account for the higher BSFC.

[SD70Dude]

erikem

I vaguely recall the C175-16 as running at a significantly higher speed than the 710G-16, which may account for the higher BSFC.

You are correct, the EMD 2 strokes max out at 850-950 RPM, depending on the engine.  Full throttle on the C175 is 1800 RPM.

[nfotis]

SD70Dude

You are correct, the EMD 2 strokes max out at 850-950 RPM, depending on the engine.  Full throttle on the C175 is 1800 RPM.

 

 

Same with the MTU R4000, they run at 1800 RPM at full throttle.

I remember reading a paper about Indian Railways ALCo 251F conversion, where they claimed 180 grams/kW-hr (I don't remember if it reached production status, though).

 

N.F.

 

[Anonymous]

Does someone have a link to papers with the fuel consumtion of C175-16 and C175-20 in locomotive service? All I found are C175s in stationary generator set.

The fuel consumption differs from standby to prime to continuous service and for 50 Hz and 60 Hz. None of them were Tier 4.

Here is a link to a data sheet of the MTU 4000 R03 series: 

https://mtu.cwshops.com/print/3232331_MTU_Rail_spec_4000_03.pdf

It contains fuel consumption at rated power and best point.

Theoretically a four-stroke diesel engine should have better fuel efficiency than its two-stroke counterpart. To really prove it the engines should be otherwise designed to the same specifics: Bore, stroke capacity, power, rpm etc.

In 1998 and 1999 the CARB initiated emission tests to find the influence of different diesel fuels: 
https://www.arb.ca.gov/fuels/diesel/102000swri_dslemssn.pdf

Tested were three UP 9-44CW and three BNSF SD70MAC. Starting on page 75 the results including fuel consumption are gathered. I have only looked into the "CARB Fuel" section and here the SD70MAC uses marginally less fuel. But it looks like the difference in this case is within the measuring accuracy.
Regards, Volker

[erikem]

SD70Dude

You are correct, the EMD 2 strokes max out at 850-950 RPM, depending on the engine.  Full throttle on the C175 is 1800 RPM.

I knew that the EMD's max out about 950RPM, but wasn't sure about the C175's. Thanks for the info.

1800rpm would imply smaller cylinder bores and shorter strokes than the 710's, which would increase the surface area to volume ratio, which in turn implies greater heat loss through the cylinder walls. The smaller cylinders and higher speed would likely increase the frictional losses for a given power output. both effects would lead to higher BSFC.

My recollection is that some ship diesels have BSFC below 0.30 lb/hp-hr.

[timz]

Think the 710 engine is 900 RPM maximum. Just the 645F3 was 950 RPM.

The C175 may be 175 mm bore?

[Anonymous]

timz

The C175 may be 175 mm bore?

You are right, the C175 has 175 mm bore and 220 mm stroke.
Regards, Volker

[Entropy]

16-710-G3C, 16-710-G3C-T2, 16-710-G3C-T3 are all 950rpm

Now one would assume a two stroke engine has a certain fuel efficiency, however you will find the two stroke engine is more thermally efficient than a four stroke engine of equal size and material construction.