Tier 4 VS Tier 3 Fuel Efficiency

[caldreamer]

I do not understand why there have been reports that the tier 4 locomotives are less fuel effiecent than the tier 3 models.  They both use the same orime mover, alternator and rectifiers.  The only real difference is the cooling of the exhaust gases.

    Caldreamer

[Overmod]

They also involve lower peak combustion temperature, part of controlling NO emission in the absence of SCR/DEF, which lowers engine thermal efficiency (hence increases fuel per hp/hr).  If there is a DPF requiring regen, expect about 6% fuel penalty for operating rich to provide enough afterheat to burn off the trapped particulates during regeneration.

[oltmannd]

What he said...

Avoiding the hassle of DEF was a big mistake which the RRs are already starting to walk back to some degree.

[Overmod]

oltmannd

Avoiding the hassle of DEF was a big mistake which the RRs are already starting to walk back to some degree.

The interesting promise of 'modern' SCR with DEF is that it can easily be used to reduce any quantity of NO in the exhaust.  Therefore once it is present the Diesel engine can easily be adjusted for much higher CR (or peak CR in a VCR engine) and any vestige of EGR removed or plated off.  In all probability the higher achievable firing temperature will reduce particulates, particularly the medically-significant nanoparticulates currently overlooked by nanny-state weasels (like those who attempted to 'game' tier 4 final to eliminate the GM two-stroke... but I digress) if a little air injection pre-or post-turbo is used, so the idiotic and largely pointless DPF that is largely for feel-good soot opacity reduction should also be removable, along with its regen penalties (or the need to be swapped out periodically for cleaning and reconditioning if not actively regenerated).

Research into very high CR via staged turbos and ceramic coatings and components allowing much higher EGT was actively pursued at Ford in the '70s.  This produced at one point (IIRC 1977) a Ranger-size pickup that easily got over 80mpg loaded at 55mph cruise.  (This goes well with the Chrysler experiment a few years later that, very reasonably to me, used the lightweight construction techniques of the early Prius and Insight on a full-size 6-passenger car, and could get in the 70mpg range even without twins.)  Ah, the roads not taken on the way to today's crop of 22mpg pregnant running shoes -- why can't we have more like the Ford Flex with light CIDI and twins instead of just GDI at lower variable boost...

Anyway, it's interesting to contemplate the lower emissions and probable fuel saving from the optimizations practical with modern SCR that controls ammonia slip correctly in all operating regimens.  I expect railroads to be cagy if not outright mendacious and impose surcharges for the "increased fuel cost" net of DEF provision and servicing - perhaps getting the political capital of a good unfounded-mandate whining campaign along the way - but it would be leaving a considerable amount of real cash on the table not to make the engine improvements as soon as practicable after 'admitting defeat' and adopting the technology...

[caldreamer]

To digress for a moment.  How diffenent would a SD70ACe-T4 ro an ES44AC-T4  with SCR and DEF added or would there be no external differences?

    Caldreamer

[bogie_engineer]

caldreamer

To digress for a moment.  How diffenent would a SD70ACe-T4 ro an ES44AC-T4  with SCR and DEF added or would there be no external differences?

    Caldreamer

 

I was hired back as a contractor at EMD in August 2010 on the day that Progress Rail took over to design the Tier 4 SD70ACe incorporating the 710 engine with a full package of DOC, DPF, and SCR which was thought at the time to all be required to meet the reg with the 710. In order to fit the emissions equipment over the engine, I had to drop the engine about 8" to meet Plate C which was the goal. To lower the engine that much required a fishbelly underframe and an integral fuel tank for strength and weight reduction. The length over endplates increased 30". The 600 gal capacity DEF tank was to be above deck inside the carbody to prevent freezing in cold weather and to preserve fuel capacity. The engine was to be isolation-mounted using rubber mounts on an extended oil pan that included support for the alternator which required spreading the centersills further apart and the integral fuel tank for support and to counter the increased weight of the isolation arrangement. To keep the weight at 420K lbs., the weight budget required a lighter truck and to make room for fuel, a 4" shorter truck wheelbase.

So needless to say, the changes to the SD70ACe for Tier 4 with 710 were extensive. While we were at it, we designed the cab to slope the windows and improve the visibility while rigidly mounting it again since we had engine isolation. The cab made it to the final T4, not much else did. 

 

Together with an expert CAD designer, we had a workable arrangement using what was known at the time. The emissions equipment hadn't been tested at that point and would have undoubtedly gotten more compact but it was roughly 30" tall, 6 feet wide, and the length of the engine and would have sat directly over it. Of course, the RR's insistence on a no DEF solution killed that arrangement and engine testing had shown the massive EGR needed on the 710 would have made the fuel consumption non-competitive so about 1.5 years into it, the decision was made to go with the 1010J. While the new engine arrangement was being designed (the only part used from the H engine was the cylinder head) I moved on to truck design again and did the GBB four-axle articulated truck used in Brazil and the Tier 4 fabricated HTCR-6 truck before I finally retired in 2015.

Dave

[caldreamer]

Thanks. that  is a great answer from an expert.

   Caldreamer

[Overmod]

bogie_engineer

While we were at it, we designed the cab to slope the windows and improve the visibility while rigidly mounting it again since we had engine isolation. The cab made it to the final T4, not much else did.

The immediate question is whether the prime-mover isolation was kept in the 1010-engined version, or what other measures were incorporated to keep out of a "Thundercab" situation.  What was actually done?  Is there lower inherent NVH with the four-stroke engine?

... engine testing had shown the massive EGR needed on the 710 would have made the fuel consumption non-competitive so about 1.5 years into it, the decision was made to go with the 1010J.

It was my observation that the test results with the 'last' test version of the 710 were within something like 0.2 percent of the mandated (and apparently arbitrarily set) NOx mandate, and that 'miss' only occurring on a relatively small part of the overall test cycle.  Was this the engine with unworkable EGR implementation (which might explain why GM did not petition to have the standard reviewed and revised) and was there any attempt to have EPA revisit the assumptions for the Tier 4 final NOx to keep a cost-effective non-SCR version of the 710 'legal' for some applications (even just for repowers of Tier 0 or 0+ locomotives)?

While the new engine arrangement was being designed (the only part used from the H engine was the cylinder head)...

Here is the promise of a definitive answer: My understanding of the 'problem' with the 265H engine was that it largely involved ultrasonic-vibration 'cavitation' (likely sonobubble collapse effect) issues in parts of the relatively thin-wall block.  Was that a factor in redesign, and what were the actual design changes made to produce a workable J-block?

[SD70Dude]

Overmod

bogie_engineer

While we were at it, we designed the cab to slope the windows and improve the visibility while rigidly mounting it again since we had engine isolation. The cab made it to the final T4, not much else did.

The immediate question is whether the prime-mover isolation was kept in the 1010-engined version, or what other measures were incorporated to keep out of a "Thundercab" situation.  What was actually done?  Is there lower inherent NVH with the four-stroke engine?

Progress lists the isolated powertrain as one of the improvements in the SD70ACe-T4 promotional material.  At any rate, whatever they did it sure seems to have worked.  While I have not yet gotten to operate any of the demonstrators CN has tested, everyone who has raves about how quiet they are. 

Here is the SD70ACe-T4 brochure:

http://s7d2.scene7.com/is/content/Caterpillar/CM20170915-63120-29009

 

Overmod

While the new engine arrangement was being designed (the only part used from the H engine was the cylinder head)...

Here is the promise of a definitive answer: My understanding of the 'problem' with the 265H engine was that it largely involved ultrasonic-vibration 'cavitation' (likely sonobubble collapse effect) issues in parts of the relatively thin-wall block.  Was that a factor in redesign, and what were the actual design changes made to produce a workable J-block?

So it IS based on the H-engine, just like how the GEVO rose from the HDL's ashes.

What "design expertise" did CAT contribute to the J-engine's design?  Their EGR systems seem to have been nothing but trouble in both on and off-road engines. 

[bogie_engineer]

EMD reluctantly accepted that engine isolation was needed for the next generation of locos. The isolated cab caused many troubles although they were quiet. There is actually an SD60 running around Pueblo that has a 12-710 with an elongated oil pan supporting and maintaining alignment with the alternator that is sitting on isolation mounts. That was to be the arrangement with the 710 going forward. Actually, our first application of engine isolation was the DE/DM30AC that I led the mechanical design on. The first iteration of a skid there had fatigue problems brought on by the new firing order 12 but a skid redesign fixed it. 

For the 1010J, the design requirement was to mount the alternator to the cast block like GE has done since day one and put isolation mounts under both the alternator feet and engine feet and this is what was done to make them so quiet. I firmly believe getting the engine vibration off the loco frame will improve the reliability of the electronics and most other systems as a side benefit. 

I can't really speak to the specific troubles on the H engine but they are working on 300 locos in China since about 2007.

So the 1010J really is a new engine with the basic cylinder geometry carried over but completely new turbos (3 of them) and extensive intercooling, aftercooling and EGR cooling plus common rail injection. When I left in 2015 engines were running in test cells but hadn't made it into a locomotive yet. CAT engine experts did look over the EMD engineer's shoulders and were part of all major milestone reviews but the design was done at EMD.

Dave

[freightcarguy]

For those of us who aren't "insiders", what is SCR and DEF?

[bogie_engineer]

SCR is selective catalytic reduction, this website describes it much better than I can:

https://www.dieselforum.org/about-clean-diesel/what-is-scr

DEF is Diesel Exhaust Fluid, the blue liquid most diesel trucks require now that is injected ahead of the SCR to reduce the NOx in the exhaust. It is basicly urea.

Dave

[Shadow the Cats owner]

It's because of DEF and SCR in the OTR side of Diesel engines my boss has seen our fleet average go from just over 5 MPG just 5 years ago to this year we are slamming over 8 MPG with bigger engines and running a faster truck speed also.  Why the 2020 engines basically only have EGR on them when they are idling.  When going down the road the computers let more DEF be used to convert the NOX into CO2 and Nitrogen.

[SD70Dude]

It seems to be well established that EGR was, and is a failure in the on-highway and smaller diesel engine markets. 

GE seems to have gotten reasonable reliability out of the Tier-IV GEVO engine, but it does use more fuel than its Tier-III counterpart.  It remains to be seen how well they will do in the long term. 

The Class I's still want nothing to do with SCR and DEF.

[bogie_engineer]

Amtrak and their state partners are going to SCR/DEF on the Charger locos with Cummins engines and Progress Rail did the F125's for Metrolink with CAT engines with SCR. GO Transit in Toronto has the MP54's with dual Cummins QSK60's with SCR so there will be plenty of experience gained on RR's in North America, just not on Class I's. Before I went back to EMD in 2010 I was working as a consultant for MPI and did the first layouts of the MP54AC retrofit to the MP40 and was able to make it all fit as the Cummins SCR package was much smaller than what EMD was proposing. My guess is that the Class 1's will eventually accept SCR for fuel savings and reliability but it won't be soon.

Dave

[SD70Dude]

How well did the 710 run with a SCR/DEF setup added on?  Was there any increase in fuel consumption?

[bogie_engineer]

I wasn't close enough to the engine guys to know for sure, but EMD 2-strokes are always negatively impacted by exhaust backpressure and surely the extra piping would add significant backpressure. Prior to Tier 4, the limit on backpressure for turbo engines was 5 inches of water for industrial/marine applications, the straight thru silencer on locomotives added very little. IIRC, at 5" H20, there was a couple of percent increase in fuel consumption. 

For the Tier 4 710, they were looking at two smaller turbos or at turbo compounding, which they are doing on the 1010J.

Dave

[Shadow the Cats owner]

Bogie that mirrors what we have found in the 4 stroke side in the OTR industry.  Heck at the start of the EGR without SCR and DPF era at one point these engines were using 30% Exhaust gas in the next charge at times to make the emisson standards.  Then we added DPF and needed to add regenerations to the mix which took on average 6 gallons of fuel to complete.  We had EGR coolers that would make engines into boat anchors when they failed mixing oil into the coolant and hydrolocking the block normally doing about 1500 RPM tends to make a heck of a mess of the rotating assembly.  Then throw in the Sulphric acid that is created from the buring of diesel and the ablation of the valves from the carbon leftover.

[rvos1979]

One would only hope that Cat learned from their mistakes with the 2007 emissions fiasco........

Lots of drivers still remember that, and the International MaxxForce boat anchor that followed a few years after.........

Getting back to trains, I wonder if the backpressure could be reduced by using turbochargers feeding a Roots blown style 710, like the old Detroit two stroke engines, but I suspect that packaging the whole works would be an issue..........

[Notch 8]

bogie_engineer

 ...we designed the cab to slope the windows and improve the visibility while rigidly mounting it again since we had engine isolation. The cab made it to the final T4, not much else did.  

 

Dave,
I would like to thank you and your fellow engineers for your design work on the SD70ACe-T4.  The sloped windows and very quiet cab are huge improvements over the SD70ACe. 

The vertically mounted windows on the SD70ACe (just like the SD60M triclops) force you to look through the reflection of the rear window on the other side of the cab.  This can be very distracting, especially at night, when you see lights streaking across your field of vision.  Many times over the years I momentarily thought someone was racing across the tracks just ahead of me.

The original, non-isolated cab SD70ACe design is horribly loud in high throttle settings – perhaps even worse than many of its predecessors.  The engine isolation on the SD70ACe-T4 has made for a wonderfully quiet cab.  Now you can actually have a cross cab conversation, while in Notch 8, without yelling at each other. 

When I started railroading in '94, I was a dyed-in-the-wool EMD fan, especially of the SD40-2s, even though they were getting long in the tooth.  Eventually though, I came to prefer GEs, any GE, from the Dash 8s on.  The SD70ACe-T4 has changed my opinion about EMD for the better.  Thank you!

Allan
Locomotive Engineer
UP Seattle Sub

[bogie_engineer]

Thanks for your kind words Allan. Like I said, I laid the groundwork but others did the detail design of the final product. I was a longtime member at trainorders.com (no longer) and the comments there about the reflections in the windows on the SD70ACe's stuck with me so I did champion that for the T4 as well as the engine isolation. The first 9 years of my career there were spent as the noise engineer doing cab, wayside, and industrial applications. Getting to an isolated cab was talked about for the -2's as we knew that isolation of the engine or cab was the only way we would do any better than the slight improvements on the -2's compared to their predessors. It was only with Conrail insisting on a quieter cab that the first isolated cabs for NA got built - there was no way the organization was ready to isolate the engine due to the alignment of the engine to generator using the rigid mounting to the underframe. I actually proposed an isolated powertrain for the SD80MAC when I started that project but management quickly shot that down in favor of the isolated cab. But as the experience with isolated cabs long term reliability issues surfaced, the management was finally ready to accept the isolated powertrain. Working as the lead mechanical engineer on the LIRR DE/DM30AC's with a small dedicated team we were able to incorporate an isolated powertrain using a skid to maintain alignment, including the equipment rack. That had it's own set of problems but did result in very quiet cabs. But when it was time to do the 1010J for Tier 4, the engine designers finally accepted mounting the alternator off the end of the engine which was always the best solution.

Dave

[Overmod]

rvos1979

Getting back to trains, I wonder if the backpressure could be reduced by using turbochargers feeding a Roots blown style 710, like the old Detroit two stroke engines, but I suspect that packaging the whole works would be an issue..........

That wouldn't get you anywhere.  The Roots is a positive-displacement blower and its load (assuming it is driven the usual EMD way via gearing from a camshaft) would be correspondingly increased by any turbocharging, whether or not the charge air delivered to it were intercooled or not.  Meanwhile of course the turbochargers when producing meaningful charge-air compression at appropriate mass flow are themselves sources of considerable exhaust backpressure (and correspondingly higher EGT and two-stroke scavenge-flow restriction)

What Mr. Goding is describing is the back pressure imposed by all the flow restrictions in the aftertreatment equipment, downstream of the turbochargers.  This could only be 'reduced' with additional driven pumping (probably not positive displacement) which could theoretically, but not particularly economically, be derived from heat extracted from the exhaust.

[Shadow the Cats owner]

Part of the problem with any 2 stroke design is the simple fact you need some sort of positve air pressure to force the next charge into the cylinders while the current one is still in them and push all the air out.  On a 2 stroke gas engine they use the piston itself to create that pressure and a set of reed valves on most small engine equipment.  On larger diesel engines they use a blower driven off the crankshaft to create that pressure.  That's why most 2 stroke engines will load faster than any 4 stroke is they are producing more power per RPM as they are always on the power stroke on the downward strokes.  On the four stroke engine you have a seperate stoke to both get the fresh air into the cylinders and get rid of the exhaust so they also tend to burn cleaner Alco's not withstanding and their turbo lag problems from governors that were not set right.  We have a farmer around here that has a older IH that was rebuilt into a monster engine in HP.  The engine is rated at over 900 HP after its latest overhaul and even when the driver stands on it no smoke from the stacks but the freaking thing screams about as loud to me as some of the videos I have seen of the old Turbine locomotives the UP had in the 60's.  

[M636C]

bogie_engineer

 Getting to an isolated cab was talked about for the -2's as we knew that isolation of the engine or cab was the only way we would do any better than the slight improvements on the -2's compared to their predessors. It was only with Conrail insisting on a quieter cab that the first isolated cabs for NA got built - there was no way the organization was ready to isolate the engine due to the alignment of the engine to generator using the rigid mounting to the underframe. I actually proposed an isolated powertrain for the SD80MAC when I started that project but management quickly shot that down in favor of the isolated cab. But as the experience with isolated cabs long term reliability issues surfaced, the management was finally ready to accept the isolated powertrain. 

Dave 

What were the reliabilty problems with isolated cabs?

I haven't heard of problems with Australian isolated cabs. These are an interesting design and are supported at waist level, just below the cab windows. This reduces the interior cab dimensions and makes it harder to lean out the windows but reduces the forces on the flexible supports. It also allows a fixed shock absorbing area in front of the cab.

One type, the JT42C, had isolated cabs at each end. These had the original 12-710 which suffered from greater vibration than the later engines with the revised firing order. One group of units, the AT42C with rigid cabs and the original 12-710, is rarely used except as trailing units now.

Could supporting the cabs at waist level reduce the problems seen in the USA?

Peter

[bogie_engineer]

The NA isolated cabs starting with the SD60I were mounted on four bushing-type isolators acting with rubber in shear to get greater deflection and lower natural bounce frequency. Eventually the isolators settled and grounded out the isolation. They also had some bad modes of vibration; if the trucks hunted, the cab would diagonally pitch and it was hard to stay in the seats, that was a particular problem on the SD90MAC/43's on a specific stretch of UP track where they set the gauge intentionally tight causing the trucks to hunt at around 65 mph. The isolated cab for the SD70ACe had redesigned isolator mounting and orientation raising the isolation frequency but still low enough to be effective.

Dave

[NorthWest]

My understanding is that sourcing the rubber bushings has become an increasingly expensive problem as the units with first generation isolated cabs have aged, and that this is part of the reason that SD70ACU rebuilds have had their cabs replaced.

[BDA]

I agree , the "cab" rides better in a 70ACe than a 90MAC .

When the 90s go into earthquake mode at lowish speeds things can get a bit violent in the cab .

[Psychot]

Was the railroads' resistance to DEF driven entirely by the cost of infrastructure to handle it, or were there other concerns?

[Overmod]

Psychot

Was the railroads' resistance to DEF driven entirely by the cost of infrastructure to handle it, or were there other concerns?

At least some of it is in the straight cost; it is seen as essentially an unfunded mandate, and with some justification it puts an outsize welfare-economic penalty in railroads for the relatively small absolute NO/NOx reduction (leveraged as it is by other pollution reductions) it actually produces in current practice.  The argument that it increases effective fuel cost is a bit specious in that most of the direct cost can be surcharged to customers just as fuel-price spikes have been.

It's also a technology with some dramatic bad press, in part due to the Government shooting itself in the foot by mandating the same sort of 'forced derating' if the DEF system fails or runs short that it imposed on motor-vehicle owners.  Railroad owners are not such fools as to accept this in freight service where even relatively small failures of locomotives can have critical results.

I do not know whether unions have weighed in on safety or other 'employee' issues, and would appreciate hearing about any opinions or actions.

[Shadow the Cats owner]

This should give you an idea of the costs of Diesel Particulate Filters as yesterday we had to replace 2 for trucks out of warrenty.  The filter alone for one of our trucks is 9 grand for a 500 HP engine.  The average repair cost for a diesel emissions control engine on a OTR truck is 25 grand when they fail with 20 grand of that being parts alone.  So based on that your looking at about figuring on displacement as each filter can only service a certain size of engine so with our engines being 15 liters.  So most locomotives the Diesel Filter would be about 108 Grand to replace when required.  The way it looks like is about a 10X increase in what it costs to repair an OTR truck compared to a Locomotive.