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Tuning a 12.7L Detroit for fuel milage only?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Deezl Smoke, Sep 21, 2012.

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  1. Sep 21, 2012 #1
    Deezl Smoke

    Deezl Smoke Medium Load Member

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    If one were to retire his old truck from service, but want to use it as a camper for those seldom allowed vacations, is it possible to tune or otherwise modify a large diesel such as the Detroit 12.7L for fuel mileage only?

    Currently 430hp. Bone stock configuration. 300hp or less would do all that is needed, but am not going to change out an engine for a camper. I am just curious what might be possible to gain some fuel mileage?

    The front driver is being removed. Fifth wheel plate gone. Full fenders. The truck is a Peterbilt 377 sbfa. It has no external air cans, frame mounted horns and under frame exhaust. So it's pretty slick thru the air already. What else can I do to gain fuel mileage?

    Thanks.
     
    Deezl Smoke, Sep 21, 2012
    Deezl Smoke, Sep 21, 2012
    #1
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  3. Sep 21, 2012 #2
    Ruthless

    Ruthless Road Train Member

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    gear it w a lower rear end ratio/drive it slower. i.e. go from 3.70 to 3.08 or lower.
     
    Ruthless, Sep 21, 2012
    Ruthless, Sep 21, 2012
    #2
  4. Sep 21, 2012 #3
    little cat 500

    little cat 500 Road Train Member

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    gearing it alittle taller should be about all you realy need not going to be pullin 80'000 pounds any more
     
    little cat 500, Sep 21, 2012
    little cat 500, Sep 21, 2012
    #3
  5. Sep 21, 2012 #4
    freightlinerman

    freightlinerman Road Train Member

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    First, turning down HP may not get you better fuel mileage. It's been proven TURNING up the HP gets better fuel mileage. The key to fuel mileage is your RIGHT FOOT. You can have 600 HP, but if you shift 1,400-1,500 you will never use that. Watch your speed too. When you're in the mountains, you get better fuel mileage with MORE power. MY dad had a Series 60, after having it derated to 455 it wouldn't climb as good and would lose fuel mileage compared to the 515 setting. Besides, turning up the power you will get better torque and won't have to use as much power to get going.
     
    freightlinerman, Sep 21, 2012
    freightlinerman, Sep 21, 2012
    #4
  7. Sep 21, 2012 #5
    Deezl Smoke

    Deezl Smoke Medium Load Member

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    Feb 12, 2011
    Hillsboro Oregon
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    Thanks. I'm geared at 3.36 now with a super 10 and low pro 22.5s. I do have a set of 11r24.5s that would sure make it look good. May have to ponder that idea.

    I dont want to de-tune it per se', but I was wondering if there is a way to fiddle with the timing or turbo sizing, etc. Since it's just empty travel tractor, even the steepest hill I'd ever encounter would'nt move the egt gauge much off idle temp.
     
    Deezl Smoke, Sep 21, 2012
    Deezl Smoke, Sep 21, 2012
    #5
  8. Sep 22, 2012 #6
    freightlinerman

    freightlinerman Road Train Member

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    Believe me, get as much power as you can safely handle. Think of this way, if you have 600 HP and use half throttle, its 300 HP you're using. Ok, not very accurate. The less effort your engine makes, the better fuel mileage.
     
    freightlinerman, Sep 22, 2012
    freightlinerman, Sep 22, 2012
    #6
  9. Sep 22, 2012 #7
    allan5oh

    allan5oh Road Train Member

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    That's kind of a myth in the industry that needs to die. Two engines making 300 hp yet one is rated at 500 and the other at 600 are working the same. They're both making 300 hp. Horsepower is the rate at which work gets done. Pushing a little less on the throttle means nothing with these electronic engines. I could make one that puts out 500 hp within the first 20% of throttle position and you'd have nothing but an on/off switch. But hey, you don't have to push on the pedal hard, so it must be better right?

    To be honest I'd rather have an engine with a slightly mushy pedal, that way it's easier to drive in bad weather.
     
    allan5oh, Sep 22, 2012
    allan5oh, Sep 22, 2012
    #7
  10. Sep 22, 2012 #8
    freightlinerman

    freightlinerman Road Train Member

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    I have an 8v71, 6V92T and 11.1 Series 60. Electronic pedals are nice.
     
    freightlinerman, Sep 22, 2012
    freightlinerman, Sep 22, 2012
    #8
  11. Sep 22, 2012 #9
    rebel127

    rebel127 Light Load Member

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    Feb 28, 2011
    monroe ct
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    Tune and turbo will help a truck hauling loads but in your case i think you would be better with some ecm tuning to adjust the timming and and fueling. the stock turbo will respond great and should do the job because at the weight from the camper you will not build heat enough to drive a turbo that would work well on a loaded truck.
     
    rebel127, Sep 22, 2012
    rebel127, Sep 22, 2012
    #9
  12. Sep 22, 2012 #10
    Deezl Smoke

    Deezl Smoke Medium Load Member

    495
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    Feb 12, 2011
    Hillsboro Oregon
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    That's what I was looking for. Can most certified shops do work on an ecm that is in spec now?
    I was actually thinking that I might already be below what it takes to drive the turbine of the stock turbo with any efficiency. I dont want to get a lot wrapped up in the project, but I'll be paying full pump price for fuel and at that, a couple thousand dollars will pay back quickly at even just 1mpg.
     
    Deezl Smoke, Sep 22, 2012
    Deezl Smoke, Sep 22, 2012
    #10
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