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Thread: Max fuel economy?

  1. #1
    Join Date
    Feb 2000
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    Montana
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    If you were building an engine for maximum fuel economy, which would you choose?

    1- A non-turbo 6.2L.
    2- A TD 6.2L.
    3- A non-turbo 6.5L.
    4- A TD 6.5L.

    I'll add more later, but I wanted you guys to think about fuel economy and what it takes to get it.

    MP

  2. #2
    john8662 Guest

    Post

    This is purely based on my 86 pickup. Non turbo, with C series calibrated injection pump truck geared with 3.08 and 700 trans.

    I vote for Non turbo 6.2L

    I'ts all in the gears and a light right foot

  3. #3
    Join Date
    Apr 2001
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    CA
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    My first answer would be N/A 6.2L, but....
    There are too many variables.

    What vehicle will it be in? 1/2, 3/4, 1 ton? Pickup? SUV? Other?
    What type of driving is to be expected?
    Towing?
    Drivetrain requirements?
    Power requirements?
    On/off highway?
    Driving habits?
    Speed expectations?

    The list could go on.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  4. #4
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    The vehicle will be a factor in answering the question as to which engine produces the best fuel economy. Also, part of the fuel economy equation is determining the intended use. We'll talk about all aspects....

    Was this a trick question?

    MP

  5. #5
    Join Date
    Dec 2002
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    Terre Haute IN
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    I would use a NA 6.2J stuffed in an 80 Olds Cutlass with a 700R4 and a rear gear ratio tuned for 1700 RPM at 70 MPH.
    99 K2500 GMC Ext Cab, 6.5TD, Heath ECM reflash, TDC Offset -1.80, Bumped Optic, FSD Isolator, Turbo Master, KD 3.5" Exhaust, 4.10s and 33x11.50, Intercooler is next.
    98 Burb 350 1/2T/4l60/246/10Bolts - Wifes Ride
    80 Olds Cutlass 6.2/Studded/700R4/12Bolt 3.30s/IP=4544 Juiced by JK/Best MPG=30
    79 Olds Cutlass, 410ci/700R4 - Currently Restoring
    1992 Mitsubishi Eclipse Turbo, currently 12PSI max boost
    39 Chevy Rat Rod
    2004 Sportsman 600
    2002 Scrambler 500
    2007 Sportsman 90
    2003 Kazuma 50
    2001 XR50
    1990 Murry 46"
    43 Total pistons!
    Email= Dr.Diesel@gmail.com WA9SDJ

  6. #6
    dieseldummy Guest

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    I would say it doesn't matter what engine. My answer is any engine with the IP calibrated to only deliver XXmm3 of fuel. Then it can only burn so much fuel as well as only have so much attanable HP.

  7. #7
    catmandoo Guest

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    well just from my experiences,my old 84 c10 with 6.2 and 700r4would run about 25-26mpg,and my 92 c1500 with n/a 6.5 with nv4500 ran a high of 27mpg on a half dozen occasions.i have since put my banks turbo on it and turned the pump up and man lots more power,yet i have still pulled 27 on occasion.they both use 3:08 gears.so if i had to chose i would probably go 6.2 with the 4500.but i really don't think it will be much more,i've been thinking of a way to hit 30mpg.but just haven't got there yet.

  8. #8
    Join Date
    Feb 2001
    Location
    Fort Worth, Texas, US
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    945

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    lots of compression, hardly any fuel delivery, small T3 based exhaust housing and wheel with about 6 pounds of boost from a T04 H3 inlet wheel. That's enough inlet air for around 180 hp, yet fuel delivery would probably be around a stock 135-140 hp c code engine. Wouldn't matter which engine as long as it had the correct pre-chambers. I'd also put it in one of our out of date bodied craftsman trucks......could weigh in at just over 3K pounds. And it deffinately needs a T56 from a late model camaro or firebird.

  9. #9
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    There are 3 or more scenarios that we'll discuss concerning engine/vehicle requirements and maximum fuel economy.

    1- Scenario #1 - Fuel economy supercedes all other prorities for your fullsize street legal pickup/Suburban.

    2- Scenario #2- You run at 75-mph on the Interstate most of the time in your pickup/Suburban without a load.

    3- Scenario #3- You use your pickup/Suburban for all sorts of family and work related driving, including towing the 7K family travel-trailer a few times a year.

    MP

  10. #10
    NH2112 Guest

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    Well for scenario #2 I'd use a 1/2 ton with OD tranny and gear it so that when in OD and at cruising speed I'm turning about 1800rpm. That would put you at about 55-60mph when turning 1800rpm in direct so your mileage while not on the interstate wouldn't suffer too badly.

  11. #11

    Post

    How about a budget fuel economy buidup. I vote for a 6.2 na in an 70's el camino with 2.56 gears and an overdrve trans.

  12. #12
    convert2diesel Guest

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    To answer scenerio 3, I have been driving the Buick Roadmaster wagon conversion now for a little over a month and this is my initial experience.

    The conversion is a "J" code tested used engine from Diesel Depot with a Hummer intake, 3 in single exhaust using low restriction muffler and resonator. 3.23 gears through a 700R4 (gasser torgue and tranny...soon to be upgraded to full diesel specs before I do our yearly sojorne to Florida in April with the Coleman).

    Drives in the city like it's butt is on fire (certainly gets alot of suprised looks) and still gives me 22 - 25 MPG (CAN), about 18 to 20 US. If I can ever get the return lines from leaking, maybe another 10%???

    2 100 mile trips on the highway at 70MPH gave me 30 and 34 MPG (CAN) respectively. Will have to change the timing gears and chain over the holidays and that should allow me to set the timing correctly. Once the temps get over 30 degrees F,with the proper timing and using 100% bio-diesel, I don't think 37 MPG is out of the question.

    Car was designed to tow and is spec'd for 7,500 lbs. The 6.2 may be a little light for this kind of wieght (will see. Friend has a 7,000 lb. Airstream that I'm going to try when the snow clears). From what I've seen to date, the current setup should have no trouble what so ever with my 2,500 lb Coleman.

    The thing that really impresses me is how smooth and effortlessly this car performs. With it's old gasser, anything over 60 MPH and this thing was humping. Add the trailer and you'd think I'd just stabbed it's mother. With the 6.2 I have a hard time keeping it under 70MPH on the highway and with the exception of the diesel rattle (music to my ears, bone of contention with my wife), it is not any noisier then the gasser.

    Will keep you appraised of further testing.

    Bill

    [ 12-19-2004, 06:11 PM: Message edited by: convert2diesel ]

  13. #13

    Post

    I like the idea of a 6.2 or 6.5 in a car, the mileage potential is much greater than in a pickup. Not to mention you can use a big, rear heel drive GM full size 70's or 80's car that wil provide a lot more room than any VW diesel car and be much less expensive on maintenance than a mercedes diesel. I would like to have a full size GM diesel car for work and just everday driving, and an Elcamino would be even better, I could pick up stuff from home depot or haul other light loads with ease.

  14. #14
    catmandoo Guest

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    convert what years your roadmaster?

  15. #15
    convert2diesel Guest

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    DieselHumvee and Catmandoo:

    I am trying to build up a conversion "Kit" for the 91 to 96 "B" body GMs. Peggy Sue is a 91 Roadmaster wagon with the trailer towing package, including the factory air shocks (ergo the single exhaust...why pray tell would they mount the compressor under the car where it gets all the road spray??)

    This chassis is basically the same as the "A" bodys built since 1978 and our kit should retrofit any of these cars easily. Probably there is more room in the "A"s. Hope to have a website up and running early in the new year.

    Oh and by the way, a full size wagon with the rear seat down, allows you to carry a 4x8 sheet of plywood with the gate up thereby negating the need for an Elcamino, though that would be a great conversion. The air shocks are good for 750 to 1,000 lbs.

    Bill

  16. #16
    Join Date
    Dec 2004
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    Janesville, WI.
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    35

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    All things being equal, a 6.2 NA, should give the best mileage.
    87, GMC, G25, 6.2, 700R4.

  17. #17
    john8662 Guest

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    I think in all fairness for this excersize MP is referring to using a 6.2 for best mileage in a vehicle that came factory equipped with a 6.2L. Mainly Gm Pickups, Blazer/Jimmy, Suburbans, and vans.

    I think that most follow Scenario # 2 in that we measure the fuel mileage on the interstate going between 70 and 75MPH. I know I for one, never look at mileage in town or in mostly mixed traffic because It'll be bad no matter what. When it needs fuel, I put it in.

    But when traveling on the highway, I always measure fuel economy, this helps me tell the condition of the engine and or powertrain.

    I've seen a best 24MPG on the highway with my rig, but I couldn't get that the last trip I took, it was a mere 19.

    Things I would do to improve fuel economy:
    -Cruise Control
    -Proper Sized Tires for Gearing (insure accuracy of miles driven)
    -Max Air flow (make note of Black smoke)
    -High Gear Ratio (but matched for speed and engine power output)
    -Probably best Fuel Economy at 1900 RPM
    -Total Weight Of Vehicle (good bye tool box full of junk).

  18. #18
    Join Date
    Oct 2000
    Location
    Walnut Creek, CA
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    294

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    I am missing something here? All things being equal a turbo diesel will produce better fuel economy than a N/A engine. Efficiency is improved in a turbo engine becuase the fuel is more efficiently burned in a compressed state and the ingition of the fuel air mixture is more powerful. If the injection pump delivers the exact same amount of fuel in both engines, the turbo engine will produce more power per stroke than the N/A engine, correct?
    1985 GMC Suburban 3/4T 4x4 Sierra Classic<BR> Mods: Banks Turbo, Propane Injection, Real HID Headlights, Milemarker Winch, 2.5 Pro Comp Lift, BFG 33\'s.

  19. #19
    Join Date
    Oct 2001
    Location
    NE CT
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    506

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    nope, not if you only need 30 hp to roll down the road.
    1996 K1500 6.5, 1984 K5 6.2 Banks both \"Stock\" (tilting hand side-side like Sammy Davis in Cannonball Run)<br /><br />Got Boost?

  20. #20
    20050420|7|006071|000022|69.19.2.78 Guest

    Cool

    so hello,

    When i have a lite foot, i can come to 7.5 liter diesel on 100 kms, in my nova 6.5 NA/4L80 combo with 2.73 gears, i think it can be better with a bigger exaust, timing gears and k&n airfilter.

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