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Peak torque X15 2021

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by 4wayflashers, Oct 29, 2021.

  1. Oct 29, 2021 #1
    4wayflashers

    4wayflashers Road Train Member

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    My truck is a slug on the hills so I’ve been downshifting to try and keep my speed. This chart suggests I shouldn’t do that. Does this really mean I should climb hills at 1000-1300 RPMs? Oh I have the 400 HP efficiency X15. Thanks.

    Edit- If you click on the HP picture it’ll take you to the Cummins webpage where I found these charts. Scroll down and you can find same charts for pretty much every Cummins engine.
    [​IMG]
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    Last edited: Oct 29, 2021
    4wayflashers, Oct 29, 2021
    4wayflashers, Oct 29, 2021
    #1
    RockinChair Thanks this.
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  3. Oct 29, 2021 #2
    mjd4277

    mjd4277 Road Train Member

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    What kind of transmission do you have in the truck? Manual or automated manual? Also what truck model?
    Remember that X15 Efficiency engines for the most part prioritize fuel efficiency over pulling power/torque(which is why Cummins made two versions of the X15,Efficiency & Performance).
    There’s a few variables that come into play-How much weight you typically pull, gear ratio, transmission, etc. My 2021 T680 has the X15 Efficiency engine equipped with the 12 speed Eaton Endurant automated manual. Typically most of the worlds we pull our close to 40,000 pounds and up. So far, I averaged around 8.4 to 8.9 miles per gallon. Sometimes more, sometimes less.
     
    mjd4277, Oct 29, 2021
    mjd4277, Oct 29, 2021
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  4. Nov 1, 2021 #3
    RockinChair

    RockinChair Road Train Member

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    It looks like peak torque and peak horsepower can be found around 1250-1300, so that's the RPM I would use.
     
    RockinChair, Nov 1, 2021
    RockinChair, Nov 1, 2021
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    4wayflashers Thanks this.
  5. Nov 2, 2021 #4
    4wayflashers

    4wayflashers Road Train Member

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    Been rolling through the hills in WV. Though I’m lighter than usual she seems to pull pretty alright at 1100. This is my second auto truck and with my last auto it was pretty much a given I would downshift to keep the revs up. On the bigger hills I’ve been gathering momentum and she will pull at around 1200-1250 no downshift. I guess I’ll get used to it. Lower revs is good, right?
     
    4wayflashers, Nov 2, 2021
    4wayflashers, Nov 2, 2021
    #4
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