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F134 powerband and gearing

Discussion in 'Early CJ5 and CJ6 Tech' started by Kodiak12060, Jul 12, 2004.

  1. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    Is see disappointment in another V6 conversion being done. I changed for what I thought was a good reason.
    Has anyone encountered a hill in a F head 4 cyl jeep that bogged things down, while near 40-45 MPH w/ 5.38 gears, and then tried the same conditions w/ an overdrive engaged? I'm wondering if 40-45 MPH in a 5.38 geared jeep, w/ stock 28"or 29" actual diameter tires, is far enough past the torque curve that an overdrive would drop it back into the powerband so you could make it up the hill w/o bogging down. Anyone have a graph of the F head torque/HP curve w/ rpm?
    That would be 2903 rpm's w/ 28" tire, going 45 mph w/ 5.38's. Where's peak torque?
     
  2. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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    Animal has a hard time at tellico on the hilly road to and from camp

    35-40 MPH is about it........With 5:38 and 30" NDT's
     
  3. Jul 12, 2004
    neptco19

    neptco19 That guy....

    Athens, GA
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    only in animal can you take those turns at 35-40 :shock: :D
     
  4. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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    I love my Jeep :D :hurrican:
     
  5. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    Would an overdrive make that hill possible by lowering the rpm's back into the rpm range of where the peak torque of the F head is. If I used the same parameters as above but the overdrive engaged it would be spinning at 2177.75 VS 2903 disengaged. Need the powerband now.
     
  6. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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    No
    IMHO its all over...........I could gain more speed by dropping into second.....or sidestepping the clutch (bad)..........
     
  7. Jul 12, 2004
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Bill, I think you just don't have enough power to overcome the increasing wind resistance with increasing speed. Wind resistance goes like the square of velocity. Cyclists really notice this abrupt increase in effort for increasing speed.

    Power=torque*rpms. If you drop the rpms by 30%, then the torque must increase by 42% just to maintain the same power, and nominally the same speed. Look at the F134 torque curve and see if there are any RPM ranges where this will occur - though it seems unlikely to me.
     
  8. Jul 12, 2004
    sparky

    sparky Sandgroper Staff Member Founder

    Perth, WA
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    Read Joel Kamumen's f-head hop up on the 3B page.

    He addresses the OD and performance issues of an F-head in the Rockies.
     
  9. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    That's what I'm trying to get at.
    Besides quick acceleration to get going and slipping the clutch to raise RPM's to hit the powerband peak torque is 114 ft lbs @2000 rpm. 2000 rpms is very low for a peak torque figure. At 45 MPH you are close to 3000 rpm's and the thing just about blows up at 4,000.
    IMHO? What's that?
    So if you had an overdrive as you hit that hill at 45 and you shift into overdrive your RPM's drop to 2177 which is just past the most powerful spot in your engine band. Maybe you sail right up the hill.
    An early jeep appears to be one of the vehicles that you upshift to accelerate.
     
  10. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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    Ok I get it..............

    In Plain English "an inbetween gear"

    Right?
     
  11. Jul 12, 2004
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    IMHO = in my humble opinion.

    From 3000 to 2177 is a reduction of 27%. If the torque is 114 at 2177, then torque must be 83 or lower at 3000 for this upshift to let you go faster. Usually torque curves increase with rpms until some limit is reached, where they start to fall off gradually. What you're suggesting is that the torque curve for the F134 falls off drastically from 2000 to 3000 rpm, which I think is not correct.
     
  12. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    What made the 1970 GS Buick 375 or 390 HP 455 Stage One faster than the 450HP Chevelle SS 454 was that the GS has a wide 510 ft lb torque peak at a low 2800 rpm's vs 500 ft lbs at 3500 0r 3700 for the Chebby.
    When it comes to engine power torque is key. Diesels make gobs of torque that's why they pull so hard. They don't rev high though.
    Back to the issue. If you are in 3rd gear and want to maintain your 45 mph up a hill, in the above discussed jeep, maybe by then shifting into overdrive and lowering the RPM's to where the peak power of the engine is made maybe you won't bog or slow down. Maybe some of us could get away w/ the 4 cyl longer if we had an overdrive to lower the rpms to go up hills.
    Ever hit a hill down shift into second and all you do is slow down. You are just putting the engine furter away from the powerband.
    Anyone follow?
    I think the torque does drop off drastically after 2000. Remember these were made for Agricultural purposes. Torque should be not that much different from that of a tractor. That is why the WWll jeeps were 4.88 geared and lowered to 5.38's the the CJ's. Torque was down low. Need a graph of the power curve!
     
  13. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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  14. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    Cool thanks.
    So you have about 5 ft lbs of torque less at idle as at 2900 rpm's.
    Is 10 ft of torque on a 108 ft lb, peak, engine significant?
    Thoughts comments?
    Is my theory valid or more like the Monty Python theory on dinosaurs or how very small rocks float?
     
  15. Jul 12, 2004
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Bill. I like you, but I think your intuition about this is wrong.

    With regards to the Buick vs. Chevy, you're mixing up quick and fast.

    Torque is more closely linked to acceleration than power. Torque is force at some length of a lever arm. You have to do work to overcome resistance, whether that be hills or air resistance. Force times distance (revolutions) is work. Work per unit time (per minute) is power. Resistance is a negative acceleration.

    Think about a Jeep moving up a hill at some constant speed. The amount of power produced by the engine exactly offset the power required to move at that speed for that distance. To go faster, the Jeep has to accelerate; ie produce an excess of power. The engine can do this one of two ways - either it can spin faster with the same amount of force, or it can produce more force at the same rpms. The only engine-specific variable here is the torque curve - how much torque can the engine produce at a specific rpm.

    For the upshift scenario you describe to be true, the power, not the torque must increase with a decrease in rpms. For this to be true, the torque curve must increase proportionally more than the rpms decrease.

    Look at the torque curve http://www.film.queensu.ca/CJ3B/Tech/EngineDyno.html
    As long as the horsepower curve slopes up, the rpms are increasing faster than the torque is decreasing. Your scenario is only possible when the horsepower curve slopes down, and that only happens above 4000rpm, if at all.
     
  16. Jul 12, 2004
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    First of all I understand what you are saying but the one flaw in this is that at a certain point horsepower will do more for the engine acceleration than torque, use any motorcycle exept a v twin Harley, they produce very little torque but they produce gobs of Horsepower. What most people need to do is recam and carburate the engine to produce about another 15% more reserve horsepower and torque and to make a flatter torque curve like some of the more modern 4 cylinders. These little engines are just from a time long ago and were not made to keep up with modern traffic and what most of us on this board actually ask of them.
     
  17. Jul 12, 2004
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    when I was running my F4 with 5.38 and OD, at freeway speeds, overdrive was engaged, 55-65 no problem; when steep hill encountered, pulled out of OD to straight 3rd; if that wasn't enough, then would shift into 2nd over(2nd gear, overdrive engaged), splitting 2nd and 3rd gear. This was with 11.00 - 15 sand float tires (prob 31s)
    either way, 3000 to 4000 rpms were maintained
    unless pulling the Bantam at Colorado altitudes, very rarely had to downshift to straight second
     
  18. Jul 12, 2004
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    You are correct I should have used quick not fast in the GM anology and I was flippant in my use of terminology. In my instance I'm not looking to accelerate just maintain speed or stop the rapid deceleration.
    In this instance a drop of approx 700 rpm's increases torque 13 ft lbs, which would not be enough to stop the drop in speed. This is why I posed the question. Thanks for taking the time to respond.
    Sounds like I made the correct decision on the V6 swap in the CJ5.
    I was thinking of doing a cable operated overdrive on the firejeep so I could drive it to the parades instead of towing it. The hills just won't make that possible but I could do a 45/50 MPH w/ it in the flats or I could just be very early before most humans are awake so I won't cause traffic, Bill
     
  19. Jul 12, 2004
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
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    No..........Lost another........... :cry:
     
  20. Jul 12, 2004
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    Billy you need to start putting a Clifford performance logo on your posts so these guys will know where to get performance parts for there F-heads before Animal is the only one left! ;)
     
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