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Low rpm diesel power and the Doubler setup question.

Discussion in 'OffRoad Design' started by FSJeeper, Apr 15, 2002.

  1. FSJeeper

    FSJeeper 1/2 ton status

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    I am hearing conflicting opinions as to if I really need a doubler setup, and that is might cause more harm than good in my application. Would like some opinions.

    I am running a heavily modified turbo diesel that makes max 300 hp and 580 ft lbs at 1800 rpm without propane. Opponents to me using a doubler setup say that the low rpm power of the diesel and the 4.56's gears in the D60/14 bolt will do everything I need it too, without the additional torque multiplication the doubler would give. In fact, some say all it will do is make me break parts quicker.

    Gas engines make max torque at a lot higher RPM than a diesel, so I do see some logic to the arguement.

    Anyone running a modified turbo diesel and a doubler? Opinions?
     
  2. pcorssmit

    pcorssmit 1/2 ton status

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    It would help to know some specs on the rest of the vehicle. My overall gearing in my DD/tow rig is around 50-55:1 (forget what the 1st is in the 4500), the motor is good for around 800 ft lbs, haven't broken anything but then again its only running 33s and I don't really wheel it.

    Pete
     
  3. FSJeeper

    FSJeeper 1/2 ton status

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    Overall gearing is 60 to 1. The truck weighs about 4000 lbs. Will be running 42" swampers.
     
  4. BlueBlazer

    BlueBlazer 1/2 ton status

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    Sorry to butt in to this post, but are you by any chance running a Cummins 4 cylinder diesel with an inline pump. If so where did you get it and for how much. If not, then disregard this. Thanks
     
  5. FSJeeper

    FSJeeper 1/2 ton status

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    It is a built up 6.5 Ltr GM Diesel. I think just about every mod that can be made to one of these has been done including professional blueprinting of everything, ported heads, polishing, shot peening and nitriding critical parts, significant removal of weight from the reciprocating assembly, gear cam drive, custom injection pump, peninsular 18 to 1 teflon/ceramic top pistons, custom banks Turbo running 16 psi, and too much other stuff to mention here. I am going to set up a web site for my truck with details and pics of the engine buildup in case anyone is interested in how well our GM diesels can be made to run and very reliably.

    New Cummins engines can be bought at adelmans.com for the best prices I have found. Lots of other good 4x4 deals there including winches so cheap you can't believe it.

    Back to the original question, is a doubler worth it for a low rpm, high torque diesel engine? Any ideas? I want to get my drivetrain finished!
     
  6. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    I think I'd like to have your motor, wow! Sounds a lot like the project on the dieselpage. And how exactly did you get that in a 4K# rig? It should pretty much leap when you stomp.

    I think you'll be able to get by without it, depending a little on the terrain of course. Regardless of how the motor is built it's nice to have low gears, it's easier on the trans, lets you slow down, etc. And with a Doubler you don't have to use it all the time.
    I've been on the trail with a couple trucks with lesser 6.2L diesels that saw nice benefits from the Doubler, one was Jim Allen's K5, another is Robert Boggio's tan sub and another customer running in Moab with us was Brett Reed. None have a motor built like yours but all are solid 6.2's or 6.5's and at crawling RPM's the turbo doesn't have a whole lot to do with it all.
    No matter what you're going to have the torque to break parts, it comes down to traction and how you drive it to keep the drivetrain in the right number of pieces.

    Hope this helps
     
  7. FSJeeper

    FSJeeper 1/2 ton status

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    The engine was based on the diesel page buildup, but a lot more work into the blueprinting, balancing, porting, etc..

    I am a bonafied CoK5 member cause I own Chevy CUCV's, but this engine is going in a FS Jeep Cherokee with the top cut off, M715 front clip and the military trim, rear wheels tubs to match the front fenders. Jeep J-10 cab top which will be removable, etc, etc. Basically a stripped down short wheel base M715 look alike.

    Thanks for your advice.
     
  8. hewl35

    hewl35 Registered Member

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    Atta way Pascal. I like hearing about your truck.
     
  9. 90blzr

    90blzr 1/2 ton status

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    HELL YEAH!! I like hearin' about that thing too! Cant wait until you get your site up!!/forums/images/icons/smile.gif
     
  10. Blazr77400

    Blazr77400 1/2 ton status

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    On my 6.2 powered Chevy(Brett Reed), the doubler helped quite a bit down in moab. Compared to the 208. If you have the chance to do it, I would.
    I explain lower gears like walking up a slope with ice on it. If you go real slow you wont slip at all. But if you move to fast you lose your traction and fall.
    Last year on the wall, I had to bump my truck over.
    This year with the doubler, I could crawl up. I think the Doubler will surprise anyone who uses it.
     
  11. FSJeeper

    FSJeeper 1/2 ton status

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    Thanks for the advice. I have decided to run the doubler. Besides the advantages of the lower gears, it will extend my drivetrain so I can use equal length front and rear driveshafts so I can carry one spare.

    Also, with the Rockwell gear splitter/OD in front of the transmission, the 32 spline SM465, and the 2 doubler boxes, I will have 32 forward gears so I do not have to worry about gearing, ever.

    Once again, thanks.
     

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