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Thread: Max fuel economy?

  1. #81
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    Apr 2004
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    spontaneous wallet consumption? Sounds worse than a 50% off sale that my wife attends.

    Yea, tried and true, perkins 354T, 12valve 6BT, my 6AT, and a few old hercules that are around, and now my newest toy, my NA6.2 sub. I looked hard for a herc 3.7dt for my jeep, before I found my 6AT. Love my 6AT, wish cummins hadn't killed it, after they bought onan. (It's my mpg king)
    My tacoma is over 310,000 and probably will be in need of a diesel repower in the next 100,000. (Always In pursuit of mpg, and the wonderful smell of a diesel....) Any tried and true for it? (other than the toy 3L?) Don't think a 6.2 would fit....

  2. #82
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    Mar 2002
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    Chehalis, Wa
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    My $0.02 on fuel quality vs. economy...On my last job, I drove many miles in a '94 Dodge flatbed dually loaded with tools. I could get fuel here in western WA at the Pacific Pride stations and would get ~16mpg. But fuel at Pac. Pride in OR and I would get ~20mpg! only thing different was the fuel. I repeated this performance at least three times. Driving style was the same as I have a hereditary abnormality...my right leg and foot bones consist entirely of LEAD. Oh, yeah and OR driving invariably involved climbing one pass or another. Logging roads always a part of the mix.

    Gregg
    Did they make a lot of these in '84??

    '84 K30 CC DRW 6.2 4911 pump,6.5 injectors, SM 465, NP205, 4.10's. seats from a Y2K CC. ongoing removal of ugly parts. '93 6.5TD turbo system.

    '84 K2500 6.2 to 454 back to 6.2, np a 833 O/D, 3.73 255/85R16
    As of 5-31-06 the 454 left my posession in exchange for a 6.2!! Install complete. 7/18/07 motor blown...where's that BB??

    '84 c10 Sub

  3. #83
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    Spotted a old Buick GN yesterday , thought that would be a sweet ride with a 6.x..and 3" duals..
    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?

  4. #84
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    Dec 2001
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    Charleston, IL
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    If i remeber right i did get an adapter from TCI Racing trans co. They have lots of adaptors. http://www.powerandperformancenews.c...&Store_Code=TC
    Good idea to use the 400 shifting parts with 350C. I believe I have seen dual pattern 350C's.
    Dan

  5. #85
    convert2diesel Guest

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    Jbell:

    Didn't get a chance to do your chart today but will work on it. As per the Tacoma, if that guy up north could shoe horn a 6.2 into a Vette, anything is possible.

    84 Convert:

    Fuel quality may not be the problem. Could it be that the station in Wasington was still pumping winter fuel? I find a 10% to 15% decrease in mileage using the 20% kerosine mix we use up here as winter diesel (#1). Also could it be a difference in altitude? Just guessing here.

    G. Gearloose:

    Having just survived fabricating a 3 inch single on the Roadmonster I can't even envision doing it twice on the same car . That also begs the question...To what benifit would dual 3 in be. I would think 2 1/2 would be more then enough. No to mention that most of the system you could buy off the shelf.

    Dan:

    Now that I am using the 6.2, my tranny options are more universal and I don't have to work around the problems normally associated with the 200R4.

    MP:

    Getting back to the topic at hand, I know I have just spent the last week advocating lowering the HP requirements as opposed to tweeking the engine but I will now digress.

    Almost without exception, anyone I know that have either installed a puffer or purchased their truck with one on has said the same thing. Namely the mileage at normal speeds has been 2 to 5 MPG less then the equivalent free breather. After reading the other posts this seems to be a universal complaint.

    Could it be that the combination of exhaust restriction and intake air restriction at low boost pressures are effecting the performance? Perhaps the following would work:

    1. Install a seperate "Swanger Air" intake and filter directly into the manifold, bypassing the turbo, with a wieghted air door designed to close at anything over atmospheric pressure allowing the turbo to pressurise the sytem when needed.

    2. Install a larger exhaust by-pass to reduce back pressure when turbo not required.

    3. Manually switched vacuum source to the wastegate, allowing the driver to activate (or de-activate) the turbo.

    Especially on the older 6.2s or the converted NA 6.5s this arrangement should return these engines to thier original selfs but would retain the turbo when it is really needed.

    Just some thoughts

    Bill

  6. #86
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    3" was just to peg the coolometer, plus Dr. Lee is a fan of the 3" with crossover,and appears to attribute a portion of his good performance to it.

    I concur a tru dual 2.5" with crossover could be adequate strictly reguarding milage.
    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?

  7. #87
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    Feb 2000
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    Montana
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    Arrow

    Personally, I think the light-load fuel economy for a TD is very close to that of N/A. If you need the extra power provided by a turbo, it would be worth the trade-off, in my opinion. However.....

    The biggest problem with a turbocharger for a strictly fuel economy rig is the nut behind the wheel. Unless there's an individual out there with a lot more willpower than myself, a typical TD owner will accelerate harder, drive faster and use the power more often than when driving N/A. This hurts fuel economy.

    Other drawbacks for a TD include cost and complication for an otherwise simple to maintain engine. But, after towing a 14' camp trailer with an N/A 6.2L for several years, I know how important a TD is when towing. Headwinds and hills are not a lot of fun for an N/A.

    MP

  8. #88
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    Jan 2004
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    Central Kentucky
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    Again I am building/reconstucting a 84' Blazer and am interested in your thoughts on goal for engine RPMs at 65 MPH? Blazer will not be used for towing much, however, hills are part of the roads here. Review of comments has me thinking about the range of 1800 to 2200. Origionally thinking about 2200 before this thread started, is 1800 hard on the engine because of loads caused by going up hills, etc? How much fuel is saved by 1800 vs 2200?
    I must also admit, enjoy putting the right foot down once in a while for that diesel fuel tank high.
    thanks,
    Les
    03\' 3500 GMC Crew Cab Duramax<br />86\' one ton SRW 6.2<br />85\' Blazer 6.2 under development

  9. #89
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    Mar 2002
    Location
    Chehalis, Wa
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    In this case I seriously doubt winter fuel. The stations I was using are mostly used by semi-trucks, so fuel turnover is rapid. Also, this was happening in the middle of summer.

    Gregg
    Did they make a lot of these in '84??

    '84 K30 CC DRW 6.2 4911 pump,6.5 injectors, SM 465, NP205, 4.10's. seats from a Y2K CC. ongoing removal of ugly parts. '93 6.5TD turbo system.

    '84 K2500 6.2 to 454 back to 6.2, np a 833 O/D, 3.73 255/85R16
    As of 5-31-06 the 454 left my posession in exchange for a 6.2!! Install complete. 7/18/07 motor blown...where's that BB??

    '84 c10 Sub

  10. #90
    Join Date
    Apr 2004
    Location
    California
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    45

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    I have not seen any reference to the benefit of reduced pumping losses when using a turbo. The back pressure in front of the turbo is free. The back pressure after the turbo may be more of a
    parasitic factor.

    Is there any scientific proof that a properly
    sized turbo will not increase your mileage by
    reducing pumping losses and providing an oxygen
    rich condition allowing complete burning of all the fuel in the chamber.

  11. #91
    Join Date
    Apr 2004
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    California
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    MP,
    The power plant I would pick for max fuel mileage
    regardless of the vehicle would be:

    6.2 - stock compression- GM wastegated turbo-
    DB 2829 Injection Pump calibrated for 1983 C
    engine. (can be turned down in a "CAR" vs "truck")

    6.2= smallest displacement.
    GM turbo= low end boost (reduces pumping losses)
    DB 2928 IP= Less hp to run.

    My $.02
    Salemone

  12. #92
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    Salemone, Good choice! I would also add a gear drive timing set, balanced rotating assembly, and matched ports.

    MP

  13. #93
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    Apr 2004
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    Thanks Convert2Diesel


  14. #94
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    Jun 2003
    Location
    Pretoria South Africa
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    MP

    Very interesting topic, what is your final conclusion?

    Most off the replies suggested tall gears (3.08).

    I get
    Danie

    1982 Blazer ("Ratau" ROAR OFF THE BIG LION in African Tswana language.) 6.2L N/A, 700R4, 3.08 gears, 33" BF's. DSG timing gears, 12" Donaldson air filter, J intake and dual 2.5" exhaust. The rest stock.

  15. #95
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    There is a point of diminishing returns. Too low and your on the pedal too much under real world conditions.

    with a 700r4, and if you hate dropping out of OD for modest grades..
    3.08 is ok if your tires are 30-31".
    33's perform better at 3.56-3.73
    35's like 4.10's

    I changed my K5 from 10b 30"/3.08 to 10.5" 35"/4.10s and got the similar corrected mileage, within a mpg; and I think it got better.
    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?

  16. #96
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    Jun 2003
    Location
    Pretoria South Africa
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    G. Gearloose

    I got most off the spares to install a turbo. At an altitude off 5500vt diesel engines need some kind of altitude compensation.

    I plan to change to gears to 3.73 or 4.1.
    I got 31
    Danie

    1982 Blazer ("Ratau" ROAR OFF THE BIG LION in African Tswana language.) 6.2L N/A, 700R4, 3.08 gears, 33" BF's. DSG timing gears, 12" Donaldson air filter, J intake and dual 2.5" exhaust. The rest stock.

  17. #97
    convert2diesel Guest

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    Well I now have some initial mileage figures for the diesel Buick.

    Just returned from a 2,500 mile trip from Ottawa to Georgia and back. Calculated in Canadian gallons they ranged from 27 MPG (#1 winter diesel through the hills of Pennsilvania) to 37 MPG on the flats through North and South Carolina (80% Bio-diesel, 20% #2 summer blend), with an overall trip average of 34MPG.

    Using the cruise control we maintained a steady 70 MPH, holding the engine at a constant 1,950 RPMs. The weather was coolish (45 to 50) except in the Northern States when it dropped to 15 in New York.

    I will now start to tweak the pump and timing, and maybe go for a higher flow injector to improve spray pattern. It is my hope that at 60 degrees and at highway speeds I can consistantly get 35 to 38 MPG. That should equate into about 21 to 25 MPG with the trailer out back.

    Bill

  18. #98
    dieseldummy Guest

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    How does that relate into us gallons?

  19. #99
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    Originally posted by convert2diesel:
    and maybe go for a higher flow injector to improve spray pattern.
    This first sounds counter-intuitive to me...could you elaborate?
    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. #100
    moondoggie Guest

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    Good Day!

    Dieseldummy asked,

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