12.7 Detroit need a new turbo (upgrade?), hauling light and best mpg?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Green461, Mar 24, 2020.

  1. benjamin260_6

    benjamin260_6 Medium Load Member

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    This was a sustained pull. He goes to each rpm and holds it there for a minute while he records the data. You're surprised by the drive to boost ratio only because you're not experienced with it - these are normal readings.

    If your EGTs are getting hotter the higher your RPM goes, you should really consider getting it tuned properly and/or switching to a better turbo because there's definitely something wrong
     
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  3. jamespmack

    jamespmack Road Train Member

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    Out of all the parts or tunes avalible. The best one for mpg is driver habits. Install a boost gauge and drive by it. Pretend there is a egg under pedal and push slow and smooth. What Pyro, when it drops bellow 300° shut it off and lower idle time. It will make your biggest improvement.

    Just did first quarter ifta. 5.95 pulling cover wagon, and hopper bottom. Hopper is short haul. Lots of idle and start and stop.
     
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  4. harold6091

    harold6091 Light Load Member

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    although i do not disagree with you with the driver habits, i also have to admit that with the volvo i had with a d12, keepint it at 1450 rpm 64mph, i would get 5.5 mpg. yet with the detroit s60 i am getting a 7.5 mpg average 1600 rpm 70 mph and i dont really watch my habits. i do not have egt or boost gauge yet so i cannot comment on the temp and boost but the only reason i would put a 171702 ever again was if i was doing 650+ hp. if not it is a waste of time and money. a k31 is more than enough. even if it breaks down every 3 years it still $700 bucks. not a big deal and super easy to replace. my turbo with a 515hp i could barely hear it . however it didnt even move the 171702
     
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  5. jamespmack

    jamespmack Road Train Member

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    I have run a 17702 with less than 650. No problem. My driving habits and my setup works perfectly for me. But everyone is different.

    Just saying, most guys chasing mpg. Should look at themselves before adding power for improved mileage.
     
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  6. turbobandit

    turbobandit Bobtail Member

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    With a stock 500 12.7, the 171702 sucks; IE making a whopping 16lbs at 1200rpm. A relatively local or regional truck with a lot of stop and starts will suffer bad mpg with that turbo.
     
  7. jamespmack

    jamespmack Road Train Member

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    Not true. And zero point running a Detroit at 1200rpm.
     
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  8. turbobandit

    turbobandit Bobtail Member

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    Don’t tell me it’s not true. I’ve proved it on my own truck. I had the 1.32 housing (The housing that comes with a 171702) and changed to a 1.15 and have gotten a 1/4 mpg improvement. I suspect there is more to be had fuel mileage wise with a K-31, though I haven’t done it yet.

    And the reason there is zero point to pull the 12.7 down to 1200rpm is precisely due to the 171702 making crap for boost.

    Keep in mind I do run locally and a little further, never more than 150 miles one way.
     
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  9. jamespmack

    jamespmack Road Train Member

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    While I agree that that turbo needs a tune with more fuel to be fully beneficial. I run covered wagon short haul, and heavy and short with hopper bottom. 500 12.7l 17702 turbo. 6.5mpg yearly average. Operating 1500-2000 rpm. I keep rpms up. I have a very moderate tune currently. 518hp at the tires. Its a .25 mpg average better than stock Garret and 100° cooler on egt with stock DD 500 program. Leaves you plenty of room to squirt alittle more fuel safely.

    Now I have dyno tested numerous times. That engine is flat at 1200 and ecm is limiting fuel, no matter how much you push that pedal. You can change this, but I'm not a fan of this unless its a race application. I take off and accelerate slow. Does not bother me. Others cry on CB behind me.
     
  10. turbobandit

    turbobandit Bobtail Member

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    The reason, the ecm limits fuel is so it doesn’t overfuel with not enough boost... the exact number of lbs of boost before the ecm gives 100% fuel, I’m not sure. Suffice it is sooner with a quicker spooling turbo. Note I’m not talking cat pulling at 1200, just an improvement over the BG 171702.
     
  11. Brettj3876

    Brettj3876 Road Train Member

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    With the 702 i don't lug much below 1400. 1200 would just be creating a bunch of heat and trailing a bunch of smoke. The few months i drove my uncle's 500 anything under 1400 it would fall flat. 1600-1650 it was happy
     
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