Detroit MPG

Discussion in 'Trucks [ Eighteen Wheelers ]' started by saddleup, Jul 21, 2013.

  1. saddleup

    saddleup Light Load Member

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    Sep 30, 2011
    magnolia, ky
    0
    Have an 03 Classic with 12.7 500hp, this was a 430/500 split but got a tune took that out,now straight 500, had torque set to 1850 and rpm set at 2150. New Donaldson free flows put on at same time. Ok mpg was at 5.4 now lucky to get 5.0 kinda hanging around 4.8 what can we do now? thanks
     
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  3. allan5oh

    allan5oh Road Train Member

    1,557
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    Jan 6, 2010
    Winnipeg, mb
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    What are you pulling, where, and at what weights? What brand/model of tires? Do you ever get any engine codes? What gearing and how fast do you run?

    Always start with the cheap stuff first such as:

    - Oil sample
    - Charge air cooler test
    - New air filter
    - Valve set
    - Dyno to test for HP *AND* blowby

    More expensive in order from cheapest to most expensive:

    - ECM tune from Rebel
    - Borg Warner 171702 turbo
    - Exhaust manifold
    - New injectors (ideally at the same time as the tune)
    - Re-gear
    - Fuel efficient tires
    - Rebuild
     
    mp4694330 Thanks this.
  4. BigJls1

    BigJls1 Medium Load Member

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    Dec 25, 2012
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    when they took it to straight 500, did they but a low nox tune it also?....
     
  5. saddleup

    saddleup Light Load Member

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    Sep 30, 2011
    magnolia, ky
    0
    Sorry, 3.70 rears, goodyears 862's, 13 speed, most loads under 30k run 67/68, already have the B/w turbo 80,000 on inframe. and no codes at time of tune 2 weeks ago
     
  6. 2bit

    2bit Light Load Member

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    Mar 13, 2012
    Medford,WI
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    Check for air in fuel also.
     
  7. Rawze

    Rawze Medium Load Member

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    Jun 29, 2013
    inmytruck
    0
    thats simply horrible fuel mileage, even for that truck.
     
  8. saddleup

    saddleup Light Load Member

    281
    137
    Sep 30, 2011
    magnolia, ky
    0
    oh and pulling lowpro stepdeck, don;t idiel,
     
    Last edited: Jul 21, 2013
  9. saddleup

    saddleup Light Load Member

    281
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    Sep 30, 2011
    magnolia, ky
    0
    truck runs great, all the power you could want pulls most hills without having to drop gears. Maybe we need a Cat!!!!!!!!!!!!!!!!!
     
  10. allan5oh

    allan5oh Road Train Member

    1,557
    555
    Jan 6, 2010
    Winnipeg, mb
    0
    I'm going to assume Goodyear 362's. Those tires are brutal for MPG. They must've put in a low NOX tune for it to drop like that, and the Detroit low nox tunes don't work very well with the BW turbo. I'm also wondering about tire size and engine rpm at speed? Try not to run above 1500 rpms. How much idle time are we talking about? How long does it take for the engine to burn a gallon of oil?

    edit: I see your response of no idle time pulling a low pro step deck. I'm assuming 19.5s or 17.5s. So we have a classic truck with bad MPG tires running fast pulling a trailer that won't pull easy and a low nox tune. I still think you should be able to get 6 mpg out of it, but barely.
     
  11. saddleup

    saddleup Light Load Member

    281
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    Sep 30, 2011
    magnolia, ky
    0
    at 70 rpms are 1650
     
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