Mileage from a 14l

Discussion in 'Ask An Owner Operator' started by Short Pull, Jan 25, 2022.

  1. Short Pull

    Short Pull Light Load Member

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    Wondering what the rest of you Detroit guys are seeing for mileage out of your engines? I have a DDEC V that Leon has had his way with. 13 spd running through 3.42 rears on tall 22” rubber. I pull a stepdeck hauling transformers across all 48 states. I typically only run 58-60 mph. I’ve tried running in 12 @1400 rpm, and 11 @1550 rpm. Regardless, seems like I’m usually around 5.5 mpg. Any thoughts from you guys that have some experience? My C-16 Cat did quite a bit better than this engine has been doing. Kind of disappointed. Any thoughts would be great! Thanks, and stay safe drivers!
     
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  3. pavrom

    pavrom Road Train Member

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    I believe detroit should be run with higher rpm ... I always ran mine at 1500 on flats
     
  4. Big Road Skateboard

    Big Road Skateboard Road Train Member

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  5. Short Pull

    Short Pull Light Load Member

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    Only idle long enough to warm up the engine in the morning and to cool things down at night. Occasionally idles at night if the temps are below zero, but that’s only happened one or two nights since I’ve owned this truck.
     
    Trucker61016 Thanks this.
  6. Short Pull

    Short Pull Light Load Member

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    I just tried running a few more rpm since it wasn’t doing very well at 1400 rpm.
     
  7. NYStarcar

    NYStarcar Light Load Member

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    That seems very low for a Detroit, I'm averaging 6.5 to 6.8 running 1550 rpms at 72 mph. Did you get around to swapping in new injectors?
     
  8. blairandgretchen

    blairandgretchen Road Train Member

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    Seems real low for a 14L. My 12.7 gets 6.25 lifetime with a hood and oversize.

    I was initially scared of higher RPM, but they seem to like 1500 minimum .

    I'm running 3:55 - 60mph in 12th at 1500, or 70mph in 13th at 1500.

    Check CAC pressure test?
     
    DUNE-T Thanks this.
  9. RedForeman

    RedForeman Momentum Conservationist

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    I've had two 14L Detroit-equipped Centuries. Both were usually in the high-5's, maybe low-6's if you tried real hard. The fuel mileage was ok, I wasn't sad when I sold them for many other reasons. The sweet spot was about 1450 rpm.

    Also had a 12.7 in a third one. Totally different animal. Would get close to 7 mpg anywhere. It was happier wound up about 100 rpm more than the 14L's. The problem was, being a Century, the rest of the truck was crumbling around a great engine.
     
    blairandgretchen Thanks this.
  10. Short Pull

    Short Pull Light Load Member

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    I haven’t had a chance to put them in yet. I ordered a set though. Factory Detroit units though. Think they’re the ones they use in the 630 hp generator. I haven’t had a chance to look into specs for them though. Not sure what the nozzle differences are? My engine guy said he typically sees about 100 more ponies at the wheels over the stock units. Anyways, I’m putting them in and switching out the turbo in February after I get back from vacation
     
    blairandgretchen Thanks this.
  11. Short Pull

    Short Pull Light Load Member

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    Checked the CAC, ran the overhead, new air filters.....pretty much went through the whole list before putting it on the road. I bought the truck off of an online auction and decided to park my Peterbilt. Ran one load to the west coast with it completely stock and that was all I could handle! When I got home various extra parts fell off of the engine, and Leon sent me his turbo and he tuned the ECM. I’m pretty happy with how it pulls now, but the mileage still sucks. I figured driving as slow as I do it would be mid 6’s to low 7’s, even being a big hooded Western Star. Nowhere near that yet
     
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