Steady State Speed vs Fuel Economy results

Discussion in 'General' started by seftonm, Mar 22, 2014.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    This weeks ride is the 27/39 mpgUS city/highway rated 2016 Nissan Altima S.

    2016 Nissan Altima S



    Temps from 55 to 59 degrees and winds out of the east at about 5 to 10 mph on the NB/SB drive segment loops.

    Speedometer offsets were consistent from 50 to 70 mph with the speedometer showing 1 mph under actual GPS speed.

    RPMs@60 mph read 1,450 and varied from 1,437 to 1,510 depending on the slight change of grades due to overpasses and topography.

    The EPA Highway Crossover occurred at 71.2 mph which is a little on the high side of my self-imposed 68 to 72 mph range but well within spec of a 39 mpg highway rated car.

  2. phoebeisis

    phoebeisis Well-Known Member

    My brother has an older CVT Altima-2007 or so
    He likes it-comfortable reliable good FE

    The Maxima has numbers-FE accel-price "better" than the pricy German sport tourers
    and a much lower selling price
    more reliable too

    The Altima-47 mpg at 60 mph- WOW
    Gotta say "who needs a Diesel"
    Heck the spark ignition cars are soooo good
    Who needs a Prius-with $2 gas

    Of course gas won't always be $2
    and CO2 will be a bigger concern in coming years
    no matter what the Republican bible says(not that the Dems are making much of an effort-gotta vacation on Martha's Vineyard-Hawaii etc)

    Various plants-animals( some are bad insects)-are MOVING NORTH
    Not sure WHAT the climate deniers have to say about that
    Growing seasons are changing

    so "gooder" MPG is always good
    xcel likes this.
  3. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Charlie:

    Agreed on all fronts except around town. The 16 Altima is a solid 30 mpg runner but it does not have a Prius like capability. ;)

  4. ALS

    ALS Super Moderator Staff Member

    I'll take my Prius over almost any gasoline car for urban and city driving. Highway on the other hand, there are more than a few cars out there that I'd sacrifice five to eight mpgs for a more comfortable ride on a long interstate drive.
    xcel likes this.
  5. rhwinger

    rhwinger Well-Known Member

    ALS, could I recommend a 2016 HSH? ;-) It has to be the most fuel efficient in it's class, and extremely comfortable.
    xcel likes this.
  6. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    From early this morning the 2016 Nissan Titan XD Platinum Reserve trim 4X4 with the 5.0L Cummins Speed vs Fuel Economy Graph.

    Temps from 46 to 48 degrees F with winds out of the East at 5 mph for the NB and SB runs.


    The speedometer error was consistent from 50 to 70 mph at 1 mph over actual.

    RPMs at 60 mph were 1,573 RPM vs the calculated 1,541.

    With the 67.5 to 70 mph crossovers from 19.0 to 18.2 mpg respectively, if the Titan XD were to have its EPA rating published, it would more than likely be set at 19 mpg.

    Some thoughts on the somewhat low results, especially at lower speeds.

    The 3.916 rear end and 6-speed final (.634) of the Nissan Titan XD is too short to compete on an efficiency basis with the ¾-tons from RAM and Chevrolet with 3.42 (Ram ¾-Ton with the 6.7L Cummins) and 3.73 (Silverado HD ¾-Ton with the 6.6L Duramax) which are running at 1,400 and 1,297 RPM@60 mph respectively.

    The other HDs are upshifting well below their peak torque and can run the slow speed stuff at just 1,000 to 1,100 RPM. The Nissan Titan XD on the other hand is upshifting unloaded at 1,600 or so right where its peak torque begins and rarely runs below 1,200 RPM before downshifting. Both of which harm city efficiency which is not what the steady states deduce anyway. It is strictly a highway efficiency measure as shown below.


    Since Nissan built the Titan XD on a HD chassis possibly capable of towing > 15,000 pounds, there was little weight savings. 7,100 to 7,500 pounds in various configurations and trims with the Cummins – vs the domestics HDs. In addition, the Titan XDs frontal area is every bit as large as the HDs from the domestics. All of which means the smaller 5.0L Cummins and its 555 lb-ft. of torque is working harder to move the approximate same mass and frontal area that the 6.6L Duramax, 6.7L Cummins and 6.7L Power Stroke are. Nissan chose to change the original spec 3.55 rear end to the 3.91 for a reason and more than likely, it was to keep the J2807 12,300 lb. tow cap in the 2WD S trim vs. falling back below 11k for many of the other configurations.

    Just a guess on my part but there is a fuel efficiency penalty for that 12K tow cap rating so if you are not towing, you have more to consider when purchasing this truck.

    For future 2017 offerings, I hope to see that 3.55 rear end reappear with maybe an 11,000 lb tow cap and a retuned transmission to take advantage of an abundance of torque at 1,100 RPM on up, not at the maximum 1,600 RPM on up as it – the 6-speed Aisin transmission - is tuned today. It would provide better efficiency at both the lower speed city work, lower NVH, and a significant improvement in highway efficiency. I think…

  7. phoebeisis

    phoebeisis Well-Known Member

    Wayne-as you say
    Not stunning FE
    compared to
    1)24 mpg-60 mph- 6.7 Cummins(from memory-might be off)which tows a zillion lbs(ok-maybe 30,000lbs- a crazy amount in any case)
    2) 40 mpg-60mph- 3.0 Ram-which tows 8500 lbs or so
    Most owners of pickups rarely tow over 8500 lbs-
    That rear end-and the lesser displacement-and 2 more pistons(friction penalty)
    The big straight 6-lot to be said for large displacement turning slowly-and fewer pistons

    Lot to be said for small-3.0TD
    in between-isn't a sweet spot-so far-which is why these mid sized TD's were cancelled before-
    they just don't deliver much fuel savings(heck any fuel savings)-
    and they cost as much-and are much much less capable than the big motors
    and not a heck of a lot more capable than the 3.0TD RAM

    Either RAM is better in most things you can measure-
    the 6.7 beats it in EVERYTHING-bet you can find them discounted in stripper form
    The little 3.0 KILLS it in FE and price-and gives up just 8500 vs 12,500 tow-
    xcel likes this.
  8. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Charlie:

    I added a multi truck Speed vs FE graph and embedded it within above. I think you are onto something with the Cummins straight 6 in the RAMs vs. V8 in the Titan XD. More friction. I am trying to remember the exact dimension from the Cummins plant tour this past summer but IIRC, Cummins/Nissan saved 14" in block length with the V8 vs I6 and this was a key dimension to fit the 5.0L Cummins under the hood of the Titan.

    2016 Nissan Titan XD

    Equipped with the 5.0L V8Cummins at the Cummins Plant.​

    There was a DPF Regen in the Titan XD that I caught on camera which put off me starting the steady states by one loop so there was nothing getting in the way of the Titan that I can think of.

    I have a 20/29 mpg rated 16 RAM 1500 HFE (RWD) with the 3.0L EcoDiesel arriving on January 4th. It has the retuned combustion control to reduce the DPF hits which should make it even more efficient than the 20/28 2014 RAM 1500 (RWD) with the 3.0L EcoDiesel we drove two summers ago!

    2014 RAM 1500 RWD with the 3.0L EcoDiesel


  9. e90diesel

    e90diesel Well-Known Member

    Those #s for the Ram 3500 drw with the 3.73 ratio are impressive. Any guess at what the srw version with the 3.42 ratio would be good for at 60 mph? With fewer rpms, less rr and better aerodynamics =27+ mpg?

    Also, I can't wait to see the results for the 2016 3.0 EcoDiesel. I wonder if the retuned combustion control to reduce dpf regens is exclusive to the HFE model.
    xcel likes this.
  10. brulaz

    brulaz New Member

    In the text, the RAM's rear end is said to be 3.42, not the 3.73 in the figure.
    And in the original article he estimates that the SRW RAM HD would get roughly 1 mpg better than drw on the EPA, if it were done.

    I'm new to this site and to this methodology. But the first thing I noticed is that there's a 19 degree F difference in operating temperatures between the RAM 3500 and the NIssan Titan XD. With the Silverado 2500 run at temps in between. Couldn't that account for some of the differences? Dunno much about where these things are tested, but up in Canada there are huge differences in winter/summer diesel fuel mix and engine operating efficiencies with temperature.
    xcel likes this.
  11. phoebeisis

    phoebeisis Well-Known Member

    Packaging -two more HUGE cylinders-1100 cc cylinders- 14 inches longer -meaning everything is `14" longer

    But RAM DODGE somehow has made that a Packaging problem
    into a styling win-
    The coolest older cars-
    always had LONG hoods
    those Huge Hitler "waving to the crowd" Nazi-Mobiles-they were cool
    Eldorado- world class looooong hood-makes me want to pimp slap someone
    XKE- long hood-cool

    Right again-I am really curious to see if it is possible to improve on 40 mpg at 60 mph-1/2 ton
    xcel likes this.
  12. e90diesel

    e90diesel Well-Known Member

    The 3500 drw isn't available with the 3.42 ratio.
    xcel likes this.
  13. brulaz

    brulaz New Member

    Think I mis-read the report. My bad.
    3.73 it was.
    xcel likes this.
  14. e90diesel

    e90diesel Well-Known Member

    I got it backwards. The Ram CTD DRW is available with 3.42, 3.73, and 4.10 ratios. The SRW trucks are only available with the 3.42 ratio.
    xcel likes this.
  15. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Brulaz:

    Welcome to CleanMPG.

    I am mixing the RAMs up in the write-up above as we have only driven the 3/4-ton with their 3.42 rear ends a few times over less than 5-mile loops at the Chrysler Proving Grounds and a Midwest Automobile Media Association Rally. The chart includes the 2015 3500 DRW with the 3.73 we drove two summers back and shows just how darn efficient that 6.7L I6 Cummins really is. I was simply making comparison commentary about the 3/4 tons because of their direct relation to the Titan XD. And in this case, how the downsized engine does not provide better efficiency.

    Temperatures do make a difference but given their mass - the XD and 3/4 tons - and temps from 45 on up, there would not be much difference for these big boys. I used to use a 0.25 percent offset for every degree below 70 degrees F but now that I have a somewhat stable temperature area to conduct the steady states in the middle of the night - on the I5 NB and SB through Camp Pendleton - offsets are rarely if ever going to be needed like I had to with the I-94 NB/SB test loops from the Il/WI border to Milwaukee and back. Wind is a far less onerous factor too.

    2014 RAM 3500

    That was an efficient towing monster with a rating of 28,500 or thereabouts!​

    IHTHs and sorry for the confusion.

  16. phoebeisis

    phoebeisis Well-Known Member

    Slight aside
    I had a 2004 Titan-the 5.6?? with 5 speed AT rated 305 hp
    and they were FULL SIZED horses
    Anyway on one long trip-Katrina evacuation 2005--Flagstaff to NOLA
    It got 19mpg-same trip -73 mph hy back then
    Suburban 21mpg-about 66 mpg hy-interstate -but plenty of road work-actual average driving speed-55-60 mph
    Tundra 15.9mpg with a cap-but drove closer to 73 mph then
    98 tacoma 24mpg AT 75 mph-4 cylinder of course
    Pilot 15.9 mpg with rood basket 22 mpg with hitch carrier- 73 mph

    In any case-my point-my Titan with that sweet gasoline motor would get VERY Close TO 22 mpg at 60 mph
    Betting current Titan-gasoline- would easily match that 5.0TD unladen AT 60 MPH-

    Yes I am PILING ON-but the gasoline Titan had a sweet motor and transmission- 1520 rpms at 60 mph in 2004-and I didn't HIT THE GAS MUCH-but it did 7.5 0-60 according to moto mag testers- QUICK

    The Gasoline version-better choice-by a lot-
    same unladen HY FE-
    much quicker
    MUCH MUCH cheaper to buy
    and NOT FREAKIN way can that sweet motor trans not tow just fine-back then it was 305 FULL SIZED horses-perhaps 380 ft lbs(guessing)-in any case it was plenty of motor.

    Once again-trying to split the difference- 6.7 CUMMINS 24MPG 3.0TD RAM 40 mpg-
    just didn't give the results they hoped for.
    The offerings on either end-are just TOO GOOD
    Not unlike the Prius-but they-the Rams - are probably fun to drive-
    and are the sort of vehicles that produce FANATIC OWNERS-repeat buyers(assuming the 3.0 TD has no problems)

    Remember that Jeep-Liberty- that had a very expensive TD?? nowhere near as good as the 3.0??
    Well folks STILL pay a premium for it-used maybe 10 years later
    truck buyers LOVE TDs-
    but the 6.7 and 3.0 are just too good to pass up in favor of the Titan TD
    and the Titan Gasser-is too good-$10,000 cheaper too

    Yes I am sour grapes in respect to most TDs-but not the Rams-they are too good
    xcel likes this.
  17. phoebeisis

    phoebeisis Well-Known Member

    Another slight aside
    In respect to 6.5 ft beds carrying 8x4 ft building material.
    There are bed extenders-sorta cages that flop over the flat tailgate
    so you can carry the material-drywall plywood etc- FLAT
    instead of tilted up on the tailgate-getting ready to bounce out-and kill some other driver
    Usually they are just long enough for 8 ft material
    and you can also get a bed hitch extender-might be adjustable-for even longer "stuff"
    I had no complaints in respect to my Titan-just needed to money so sold it and the pilot and the Prism-get a prius and ancient suburban-improved family MPG to 30mpg+ from 18mpg or so
    The Titan was a good truck(there were some folks with rear end-Dana 44 re-do fixed by now-problems-but it was a nice truck-sweet nissan motor trans
    xcel likes this.
  18. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    How about a pickup with a real , honest-to-goodness , 8 foot bed ? Or is it more important to have two extra doors ? Jeez.
    xcel and JonNC like this.
  19. JonNC

    JonNC Driving Smarter Since 06/07/2011

    What do you think trucks are for, utility?
    That's crazy talk, those things are built to ride around in!
    xcel likes this.
  20. phoebeisis

    phoebeisis Well-Known Member

    Surely 1/2 ton standard cabs with 8' beds are still available?
    My 1980 D-100-just 3700 lbs-was a standard cab 8' bed-vinyl seats no ac-roll down windows with the little wing vent(good thing because Dodge QC wasn't so good back then-windows froze-rusted-shut in 1983 -so the vent was it for 3 more years)
    There must be standard cabs with 8 ft beds??
    xcel likes this.

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