Fuel Consumption GP38 v. 40

Found this interesting table regarding fuel consumption in gallons per hour on GP38s vs GP40s:

GP38 GP40
Idle 5.0 5.5
Notch 1 7.0 7.4
Notch 2 16.0 24.9
Notch 3 31.4 41.4
Notch 4 46.8 57.2
Notch 5 63.8 79.0
Notch 6 83.1 108.5
Notch 7 102.8 145.8
Notch 8 122.4 167.7

PVRX1 wrote:Found this interesting table regarding fuel consumption in gallons per hour on GP38s vs GP40s:

GP38 GP40
Idle 5.0 5.5
Notch 1 7.0 7.4
Notch 2 16.0 24.9
Notch 3 31.4 41.4
Notch 4 46.8 57.2
Notch 5 63.8 79.0
Notch 6 83.1 108.5
Notch 7 102.8 145.8
Notch 8 122.4 167.7

Yep.. the GP 40 is more fuel efficient.

I assume you're basing efficiency on comparable horsepower? The 40's use about 30% more fuel from Notch 3 on up.

Those are interesting but pretty much meaningless statistics as presented.

What IS useful is to compare power developed vs fuel consumed by each. In other words to estimate the relative fuel economy of each type while actually pulling a train.


For the -38 at notch 8: 2,000 HP/122.4 gal/hr = 16.3 HP-hr per gallon consumed

For the -40 at notch 8: 3,000 HP/167.7 gal/hr = 17.9 HP-hr per gallon consumed


The -40 is thus about 10% more fuel efficient than the -38, at least at notch 8. Further it's not unreasonable to assume similar fuel consumption differences at lower notch settings - except of course at idle.

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Or look at it another way: Assume equivalent 6,000 HP consists - ie. (3) GP38's and (2) GP 40's - each operating at notch 8 for 1 hour. How much fuel will each consume while doing the same amount of work:


-38: 3 units @ 122.4 gph/unit = 367.3 gallons

-40: 2 units @ 167.7 gph/unit = 335.4 gallons


Now if you were buying the fuel, which would you prefer pulling your train?!!

This may be one reason why Guilford got rid of their GP38s in favor of GP40s. If there's one thing they know how to do, it's save money.

Farmallbob,
I work for a small railroad and the accountants are comparing the fuel consumption of GP40's versus GP16's.
The GP16's pull four times the amount of cars, however the GP40's use twice the amount of fuel.
What are your thoughts?
bbzacraig

If the 16's are pulling 4 times the cars of the 40's, I might suggest actually placing the 40's "online", and seeing how they pull then. 4 times as many cars. (the 40 pulls 40 loads, the 16 pulls 160) Yeah, right. The EMD fuel consumption chart, in my hand, shows a GP-40, with the 16-6453B consuming 163.7 GPH. The GP-16 with the 16-567C uses 114.6 GPH, both measured in run 8. This is approximately 25% higher in fuel consumption, per hour, or one quarter more, which is significantly less, than double. the ratings across the rest of the look like this:
7th: 131.5 vs. 85.3
6th: 99.0 vs. 67.3
5th: 78.8 vs. 50.8
4th: 59.8 vs. 36.6
3rd: 43.6 vs. 24.3
2nd: 25.1 vs. 14.3
1st: 9.2 vs. 6.1
idle: 5.1 vs. 3.7

These ratings are at 60 degrees fahreneit with barometric pressure readings at 28.86 in. hg. Having run both models mentioned, and running them both in MU'ed applications, my experience has been the 40's will out-pull the 16's readily. Even with some seriously low gearing, the weight of the 40's equates to more tractive effort to move the train, and almost double the HP, to keep it moving, once you get it rolling. The 40 you are using must be dying, or maybe one of the trucks is cut-out. The facts don't add up.......

(for Farmall Bob) My chart shows the 40 at 163.7 GPH, with the 12-645E38. The 38 shows 124.1 GPH, with the 16-645E. Less with the 40, more with the 38, even though it's only a couple of gallons. Both series are Dash-2 types, not 'straight" numbers. Regards

(for PVRX) The GP-38-2 fuel consumption chart I have, shows the following numbers:

low idle: 3.5
idle: 4.5
1st: 7.8
2nd: 17.8
3rd: 32.8
4th: 47.6
5th: 64.2
6th: 82.5
7th: 103.3
8th: 124.1
These are slightly different, although the difference could be between Dash-2 series, or due to temp variants, and altitude differences.

FarmallBob wrote:


Or look at it another way: Assume equivalent 6,000 HP consists - ie. (3) GP38's and (2) GP 40's - each operating at notch 8 for 1 hour. How much fuel will each consume while doing the same amount of work:


-38: 3 units @ 122.4 gph/unit = 367.3 gallons

-40: 2 units @ 167.7 gph/unit = 335.4 gallons


Now if you were buying the fuel, which would you prefer pulling your train?!!

Simply out of curiosity: Wouldn't the 12 axles of the three GP38s ( due to higher tractive effort 3 GP38s weigh more than two GP40s...IIRC) be able to lug a heavier train albeit at a lesser rate of acceleration?

Golden, you would be one hell of an instructor! Any green horn who you train (no pun intended) is given some great knowledge and probably knows how to hog pretty good as well.

When one compares fuel consumption rates, it becomes necessary to bring up the specific duty cycle that the unit will take on. In other words, what will be the typical profile of use for the unit? Line haul, heavy tonnage? Higher speed line haul? Yard switching? Local switching with predominently light tonnage?

Here's how Environment Canada defines it:

"Duty Cycle: The duty cycle for a locomotive refers to the percentage of time the locomotive is operated at different power settings. Locomotives have eight power settings or "notches," plus low idle, idle, and dynamic braking settings."

Also, the maintenance costs have to be factored in. Quite frequently these days, GP40s in the secondary/tertiary market are being "de-turbo-ized" (I made up that word) so that they can be used in a local switching or light tonnage, lower speed operation without the higher cost of maintaining a turbocharged engine -- essentially making them into GP38s.

You want to move more tonnage at higher speed? Then you need more horsepower to overcome motor "counter" voltage and make those traction motors turn at a higher speed. Add a turbo to a GP38 (16-645) and you get 1000 extra horsepower going for that purpose. It may be more efficient, but it will still burn more fuel, in total, in that application (and do it much better). And cost you more to keep together!

GP38s still remain a favorite of short lines because they are so darned dependable and functional, even after all these years.

If you look at typical composite duty cycles of whole fleets of locomotives, you will rarely see one for which less than 50% of the time is in "idle." 55% to 60% is common. Notch 8 is way down on the list, usually, in percentage.

bbzacraig wrote:Farmallbob,
I work for a small railroad and the accountants are comparing the fuel consumption of GP40's versus GP16's.
The GP16's pull four times the amount of cars, however the GP40's use twice the amount of fuel.
What are your thoughts?
bbzacraig

With all due respect, the data as you present it is anecdotal at best - not much different than a toothpaste's claim it "whitens teeth better"...

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To make valid locomotive fuel consumption comparisons, ALL the following variables must be clearly stated then held equal for both engine sets:
- Trailing tonnage
- Number of trailing axles
- Route profile
- Speed profile over the route - including total number of starts/stops, acceleration/deceleration rates, use of dynamic braking, etc
- Amount of time engines spend idling, pumping air, etc
- Ambient conditions (temperature, barometer, wind, etc)
- etc.

Most accurate would be to utilize a dynamometer car while holding the above variables constant. Then use the data collected by the dyno to compare drawbar horsepower-hours delivered vs the quantity of fuel consumed for each locomotive set. Only then can one draw truly meaningful conclusions regarding relative fuel economy! ...FB

Hi All,

The data seems to agree with the old Union Pacific philosophy, High horsepower, fewer engines, better economy. And that is the basic reason for a Big Boy, both the steamer, and the Diesel, the DD-40AX. UP called them Centennials.

Simply out of curiosity: Wouldn't the 12 axles of the three GP38s ( due to higher tractive effort 3 GP38s weigh more than two GP40s...IIRC) be able to lug a heavier train albeit at a lesser rate of acceleration?

Yes, three GP38's would out-pull two GP40's at lower speeds. In fact, on drag freights at 10 mph, a GP40 would not actually be producing 3000 horsepower. Power is reduced to prevent wheelslip--you can actually hear a more muffled exhaust sound and a lower turbocharger whine even though the engine is still turning 900 rpm. In that case, a GP40 would have no advantage over a GP38, and in fact two SD40's would be a closer match for three GP38's.

However, the ultimate solution is to take two GP40's and attach slugs to them. That's what the St. Lawrence & Atlantic has done next to where I live. A few years ago, their trains were powered largely by four-unit sets of GP38-2's (reliable and adored by the crews, but expensive to lease and not fuel-efficient). Now, their main road power is rebuilt (to Dash-3 standards) GP40's and GP40X's with slugs, usually used in two pairs. Two turbocharged 645s in place of four Roots-blown 645s, moving the same tonnage at almost the same speed, makes for significant fuel and maintenance savings. Further savings result from the fact that the engines are in run-8 extensively, where they operate more efficiently than in lower throttle positions.

dieselsmoke wrote:Hi does anyone have any similar data on new GE engines (HDL) from GEVO and AC6000CW locomotives.

This is the EMD forum. Ask those toaster quesions somewhere else. Thanks.

Note to all. This topic regards GP-38's vs. GP-40's. Don't add other motors, or prime movers into this thread. THANKS