GP38-2s vs turbocharged GPs

[Lyon_Wonder]

GP38-2s are very popular with the railroads, so much so that higher hp GP40s and 50s are being rebuilt into GP38-2s. NS recently rebuilt GP50s into GP38-2s, and in 2006 BNSF contracted a similar rebuild for other second-hand engines. Is their a cost advantage to operate a GP38-class loco over a turbo charged GP40 or 50? Does a non-turbocharged 645 burn less fuel per mile than it’s turbocharged counterpart? Back in the 1970s and 80s EMD also marketed the GP39-2, which has a 12-cylinder turnbocharged 2300 hp 645E instead of a GP38-2's aspirated 16-cylinder 2000 hp 645E. For some reason this loco wasn’t as popular, only a few hundred GP39-2s built compared to over a couple thousand GP38-2s.

[Boomer Red]

         Turbo charging usually means that a locomotive is more fuel efficient and that is why EMD created the GP39-2. This unit went into production at around the same time as the oil crisis in the US and seemed quite logical. The problem is that turbo chargers are just another part that can fail so if you don't really need them there is no point in having them. Also the reason that higher horse power units are being made into 38s is that the 38's have proven themselves as very useful in jobs like switching service where high HP is not really an issue. And as more units like C44s and SD70s come around these high horsepower 4axle units are being bumped into less demanding roles. If all your doing is shunting cars in the yard than you don't really need 3000 or 3500 HP, 2000 HP is more than enough and won't wear out your engine as quickly.

[J. Edgar]

 not just for yard work....since its a "road" locomotive the 38's and 38-2's make good local/branch engines......kinda like a consolidation in the 40's and 50's....maid of all work....reliable...easy to work with...

[oltmannd]

I'll add that turbos are not just one more part to fail, but an EXPENSIVE part.  Tens of thousands to rebuild one plus 70 man-hours to R&R (if you have the shop equipment to do it)

 If you're only burning $50,000 a year in local service, and the turbo will save you 10%......  versus $400,000 per year in road service.....

[BentnoseWillie]

My understanding is as follows. Feel free to correct

Meeting the current EPA emissions requirements for locomotives (commonly referred to as "Tier II") involves using an enhanced cooling system; extra radiator size is part of the reason for the "flares" on an SD70M-2. The carbody of a four-axle locomotive isn't physically large enough to easily fit such a radiator, and newer power has been bumping such engines to yard and branchline service, where their extra horsepower can't be put to use.

The solution? Well, the new requirements only apply only to locomotives above 2000 HP, so if these engines get rebuilt without their turbos and derated to 2000HP, the owners get a "new" low-horsepower engine for local or yard service, they don't have to go through the pain of trying to make a GP Tier II compliant, and they eliminate the maintenance of a turbocharger in an installation where it's of limited operational benefit anyway.

[trainfan1221]

Also keep in mind that horsepower for a locomotive can mean different things.  I have read that theoretically a GP38 and GP40 had the same power and could pull equivalent amounts.  But the GP40 would have been able to do it faster.  Switchers have comparatively  little HP, but can pull quite a bit, but slowly.  As has already been said, a turbocharger is just one more thing to repair if not needed.  The advantage the GP39s had was that they could operate at higher altitudes than GP38s.

[Boomer Red]

             I wonder why it seems that CN and CP are the only railroads that aren't embracing this trend of making GP40s etc into GP38s. CP does have some Hybrids in yard service but CN seems to be retiring all of its high HP BBs. What will happen in the future when all of those     GP38-2 and GP9RM units in yard service reach the end of their life? CNs fleet of actual switchers (ie.SW1200RS) is so small now that it would hardly be able to service the needs of one of the larger yards like MacMillan. Oh well I suppose soon I'll be watching a C44 switch the Moncton yard, they all ready use SD40 units sometimes.  

[J. Edgar]

Also keep in mind that horsepower for a locomotive can mean different things.  I have read that theoretically a GP38 and GP40 had the same power and could pull equivalent amounts.  But the GP40 would have been able to do it faster.  Switchers have comparatively  little HP, but can pull quite a bit, but slowly.  As has already been said, a turbocharger is just one more thing to repair if not needed.  The advantage the GP39s had was that they could operate at higher altitudes than GP38s.

 

 same therory with cars....its Torqe that gets you moving but its Horsepower that keeps you moving....the more horses the "easier" maintain high speed

granted the transmisson of power is a lot different but the curve is simular i would assume

[silicon212]

Also keep in mind that horsepower for a locomotive can mean different things.  I have read that theoretically a GP38 and GP40 had the same power and could pull equivalent amounts.  But the GP40 would have been able to do it faster.  Switchers have comparatively  little HP, but can pull quite a bit, but slowly.  As has already been said, a turbocharger is just one more thing to repair if not needed.  The advantage the GP39s had was that they could operate at higher altitudes than GP38s.

 

 same therory with cars....its Torqe that gets you moving but its Horsepower that keeps you moving....the more horses the "easier" maintain high speed

granted the transmisson of power is a lot different but the curve is simular i would assume

 

"Horsepower" really is a misleading term to describe the power capability of a rotating energy source, such as an engine.  In this case, horsepower is a measurement of torque over time - i.e. torque multiplied by RPM, divided by 5,250 (the work pulling a weight of 5,250 pounds one foot in one second equals one horsepower).  When you look at power curves on an engine, you will note that torque and horsepower are ALWAYS equal at 5,250 RPM on a hypothetical rotational energy source.

Let's compare two different things here really quick - for example, we have a hypothetical nitromethane powered drag car that produces 6,000 HP and can turn at 9,000 RPM.  Secondly, we have a GP60 locomotive that can produce 3,800 HP and the engine turns at 900 RPM.

The layperson would think that by 6,000 HP, the drag car is more powerful than the locomotive, but when you do the math, you arrive at what's truly the difference - and that is torque.

At 9,000 RPM, the drag engine is producing 3,500 ft-lb torque to achieve its 6,000HP.  Not a small number - but let's look at the EMD.  It's producing its 3,800 HP at 900 RPM - 1/10th that of the dragster - and the usable torque production is close to 22,200 ft. lb.  There's the difference.

Now, if that EMD 16-710G3 could rotate at 9,000 RPM that would be a 38,000 HP engine!

- Gary, railfan and engine builder. :)

[Cederstrand]

So, what would a person need to do to create an N scale locomotive capable of putting out 1/2HP to set a new world record for pulling the longest N scale model train in history?

Kidding aside, that was an easy to understand comparison, Edgar. Interesting thread.

Rob 

[Randy Stahl]

I'll add that turbos are not just one more part to fail, but an EXPENSIVE part.  Tens of thousands to rebuild one plus 70 man-hours to R&R (if you have the shop equipment to do it)

 If you're only burning $50,000 a year in local service, and the turbo will save you 10%......  versus $400,000 per year in road service.....

And remember that an EMD turbo will only rob power from you unless the turbo is running off the clutch, notch 7 and up .

[oltmannd]

I'll add that turbos are not just one more part to fail, but an EXPENSIVE part.  Tens of thousands to rebuild one plus 70 man-hours to R&R (if you have the shop equipment to do it)

 If you're only burning $50,000 a year in local service, and the turbo will save you 10%......  versus $400,000 per year in road service.....

And remember that an EMD turbo will only rob power from you unless the turbo is running off the clutch, notch 7 and up .

Randy-

 You still get some contribution from the turbine even when the clutch isn't freewheeling.  In notches 7 and 8 the turbine is doing all the work.  In notch 1, the turbine is doing almost nothing.

Here's some numbers

loco	notch	THP	gal/hr	gal/HP-hr
GP38	6	1438	82.5	0.057371
GP38	8	2004	123	0.061377
GP40	6	1939	106	0.054667
GP40	8	3074	168.7	0.05488
eff advantage for GP40 in 6 vs GP38 in 8 =				11%

[Randy Stahl]

I'll add that turbos are not just one more part to fail, but an EXPENSIVE part.  Tens of thousands to rebuild one plus 70 man-hours to R&R (if you have the shop equipment to do it)

 If you're only burning $50,000 a year in local service, and the turbo will save you 10%......  versus $400,000 per year in road service.....

And remember that an EMD turbo will only rob power from you unless the turbo is running off the clutch, notch 7 and up .

Randy-

 You still get some contribution from the turbine even when the clutch isn't freewheeling.  In notches 7 and 8 the turbine is doing all the work.  In notch 1, the turbine is doing almost nothing.

Here's some numbers

loco	notch	THP	gal/hr	gal/HP-hr
GP38	6	1438	82.5	0.057371
GP38	8	2004	123	0.061377
GP40	6	1939	106	0.054667
GP40	8	3074	168.7	0.05488
eff advantage for GP40 in 6 vs GP38 in 8 =				11%

Yes , you are right on the money with the numbers but I think for the most part railroads are getting rid of the turbo's because the types of service do not use the turbo's to thier greatest advantage, the best burn for the buck is notch 8, not slapping the throttle around kicking cars.  They belong on the mainline!!

 

Some railroads have in fact "pinned" the turbo's making it impossible for the turbo to come off the clutch , of course this is done to eliminate wear on the clutch , the #1 cause of EMD turbo failures .

CSX has some MP15t locomotives that have clutchless turbo's.

[Cris_261]

One thing I've noticed on the GP40s that UP has had rebuilt into "GP38s" is that the rebuilt locomotives still have the three radiator fans on top of the long hood. Are all three fans still used, or is one of the fans, but not the shroud, removed?

[Boomer Red]

I'm not sure about these particular units but I imagine all three were left in place. Nothing would really be gained by removing one of them and extra cooling capacity is always a good thing for any internal combustion engine. Considering how much time locomotives sit idling and how full throttle doesn't always mean moving very fast it doesn't take long for things to heat up!

[MopacBarrettTunnel]

One thing I've noticed on the GP40s that UP has had rebuilt into "GP38s" is that the rebuilt locomotives still have the three radiator fans on top of the long hood. Are all three fans still used, or is one of the fans, but not the shroud, removed?

I know that the "GP-38's" rebuilt by MK/MPI in Boisie retained all 3 fans and the larger 40-series radiators for the extra cooling capacity, as has been speculated.  During the rebuild, new cores were installed, and the fans were wired to operate individually in rotation when needed, rather than "all on, all off" as in the original design.  I'm told this new feature was added to "equalize the fan-motor wear rates."

[timz]

the fans were wired to operate individually in rotation when needed, rather than "all on, all off" as in the original design. 

I'll check the manual, but for now I'm guessing GP40/GP40-2 radiator fans weren't "all on, all off".

[Randy Stahl]

Engine fans on older locomotives would turn on and off depending on engine temp. # 1 fan would turn on at approx 175 deg, no 2 fan at 195 deg and #3fan around 215 deg. As you can see # 1 fan gets the most cycling and as such will be the first to fail. Whereas # 3 fan gets the least amount of cycling therefore will last much longer. There are electronic fan controllers that cycle all the cooling fans equally making the wear on the fans even thereby saving failures on fans.  

[WSOR 3801]

Most of the ex-UP SD40-2s that WSOR has seem to have these fan controllers.  The ex-MP SD40-2s also have the MP "fuel-saver" switch.  Anybody else know what that does?

[mudchicken]

If you set all your fuel racks up to burn fuel at 1000 foot elevation or lower , those GP39-2's in Colorado running around between 3800 and  8000 feet suddenly are very attractive compared to the GP38...