Tier 4 VS Tier 3 Fuel Efficiency

[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?

[caldreamer]

Thanks. that  is a great answer from an expert.

   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]

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

[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...

[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]

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.

[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