X-15 Cummins thread

Discussion in 'Peterbilt Forum' started by KB3MMX, Feb 26, 2018.

  1. Masonry

    Masonry Bobtail Member

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    Oct 11, 2020
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    I Bought a New Pete 2020 , 389 with 565 Cummins.. 1850 Torque .Auto Shift. This truck is a Dog going up steep hills Loaded at 80,000 going about 40 to 45 MPH using manual to downshift occasionally... this truck has 2040 miles on it , Is this pulling power going to get better as the Engine goes through its break-in period?
     
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  3. JonJon78

    JonJon78 Road Train Member

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    My guess would be its either the torque or auto that is the problem.

    I have a manual 18speed 565/2050 and since day 1 its been a beast going up hills loaded...
     
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  4. Masonry

    Masonry Bobtail Member

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    Oct 11, 2020
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    I have the same Truck Pete 2020 565/1850 w/auto transmission 13 Speed ... 3.55 rears .. I posted earlier I have over 2000 miles on it and a little disappointed with climbing some of these steeper hills..running about 40 to 45 mph going up these hills. do you think maybe it will get stronger after it breaks in a little more
     
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  5. Masonry

    Masonry Bobtail Member

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    Oct 11, 2020
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    Thanks for replying , there’s nothing I can do with the torque or is there?? maybe With the auto transmission I can have them gear it down a little? Does the Engine get stronger after break-in period?
    Thanks
     
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  6. Masonry

    Masonry Bobtail Member

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    Oct 11, 2020
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    Sorry, I just read your message about your truck being strong on day one.... my salesman sold me on the 1850 torque , I think because of fuel savings? My truck has a day cab on it so I’m not sure how much more I would be burning in fuel..
     
  7. GoldDot40

    GoldDot40 Light Load Member

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    Athens, GA
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    I'm in a 2021 Pete 389 w/ IX15 500/1850, 18sp, and 3.73 axle. This truck falls flat on it's face at 1700 RPM. Peterbilt nor Cummins will even consider raising the governor to just 2000 RPM. Because of that, I have to downshift a lot in the GA mountains even when it's pulling like a champ...then hits the 1700 ceiling and is unresponsive until it falls back to around 1400 while losing precious momentum.

    Our 2007 Pete 379 with 18sp and 3.55 axles just got a brand new crate ISX15 and the ECU is modified to allow it to spin up to 2150 RPM and the difference is night and day. It will absolutely run circles around this new truck.
     
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  8. Jax Graddy

    Jax Graddy Bobtail Member

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    Jun 23, 2020
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    GoldDot40 - From my understanding, the X-15 engine's governed speed is 1,700 rpm. Seems that should be the issue in the 2021, unless I'm not understanding. Course you probably realize that, and is why you mention raising the governed speed.

    I'm looking into OTR powertrain options with the X-15 efficiency. I would love to hear a few opinions from current X-15E drivers as to just how low that engine will run before it peters out and needs a downshift. The torque curves show it hitting max torque down as low as ~970 rpm. But the hp is down near 300 at that point and I don't think it's going to want to even hold speed that low.

    What I would want to know is ... at how low of an RPM will it run on the flat / level and still pull effectively / comfortably?
     
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  9. AKDoug

    AKDoug Medium Load Member

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    The problem is that the X-15 and all the ISX family can not handle low RPM lugging. It shortens engine life drastically. 1500+ should be where it's run.
     
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  10. RockinChair

    RockinChair Road Train Member

    Our X-15 engines have been great! We've not had any issues at our terminal, and I haven't heard of any of any from the other terminals either.

    I like it even better than the 15 liter ISX, and a whole lot better than the MaxxForce.
     
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  11. GoldDot40

    GoldDot40 Light Load Member

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    Jul 20, 2018
    Athens, GA
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    Mine likes 1500 rpm on flat open roads. There's a lot of times, I can simply flip the splitter down to negotiate a slight incline without having to downshift. I pull 93,000 lbs just about every other load. Mine does NOT like lugging less than 1000ish rpm.

    Yes, even though this engine is capped @ 1700...it pulls pretty well all the way up to that point and I know it would pull hard past that if the ECU would allow it. Every now and then, I can finagle 1800 rpm (for whatever reason), I can just tell it wants more. I've been shifting around 1600 rpm to get as much as it will allow to get me rolling good.
     
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