4-Speed In A Blown Application ?

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by TOL, Mar 6, 2018.

  1. TOL

    TOL Active Member

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    Weird question......

    Anyone ever try a 4-Speed in a blown application? Any advantages or disadvantages over a 3-Speed that spring to mind apart from a bit more trans weight and length?

    Picture maybe a high overdrive C screw atop a smaller cube but highly strung RPM motor type deal.

    Thx.
     
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  2. Comax Racing

    Comax Racing Member

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    I'm going to say it might have something to do with your 1st gear ratio with an extra gear added in over a 3 spd.

    That's my 2 cents
    Corey
     
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  3. Mike Canter

    Mike Canter Top Dragster

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    The latest trend seems to be running four speeds in blow promods. Keeps the rpm and boost up.
     
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  4. jay70cuda

    jay70cuda Member

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    4 speed?? You may be late to the party. Liberty is making a 6 speed for racing applications with a converter or lockup . Ratio is your best friend.
     
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  5. Mike Canter

    Mike Canter Top Dragster

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    But that wasn’t TOL’s question. I know Liberty make all those combinations but TOL asked about a 4 speed
     
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  6. TOL

    TOL Active Member

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    Thanks Mike. Is there a rough ballpark for what people are gaining by going to 4 vs 3 ?
     
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  7. Mike Canter

    Mike Canter Top Dragster

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    Don’t have any data. NHRA only allows three speed in PM blower cars. A lot of blower cars in ProBoost are using more gears and seems to work. In the old days we thought the hemi worked better when always under load.
     
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  8. sean70ss

    sean70ss Member

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    You want a 25-30% drop per gear, rear ratio 4.30-4.56
     
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  9. turbo69camaro

    turbo69camaro Member

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    Back in the day most ran 4 speeds and in the quest to slow the blown cars down they made the 3 speed rule
     
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  10. Mike Canter

    Mike Canter Top Dragster

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    When was that?
     
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  11. mogenss

    mogenss Member

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    When the revs go up the torque curve usually gets more narrow and pointed . So the higher you rev and a more narrow and pointed it makes an advantage to have less RPM drop on the shifts.

    I can't help to think about what was going on in pro stock many years ago when HP/RPM/cost kept going up and up.
     
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  12. kosky racing

    kosky racing Comp Eliminator

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    Mike -TAD hasnt been allowed anything but a 3 speed for about 30-35 years,A-fuel have to be direct drive-no tranny
     
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  13. Mike Canter

    Mike Canter Top Dragster

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    Yes Mike, that’s why I asked when was that.
     
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  14. turbo69camaro

    turbo69camaro Member

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    Back in the 90's when IHRA pro mod had 50 plus cars for every race the blower cars were getting to fast...was not talking TAD or TAFC
     
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  15. Mike Canter

    Mike Canter Top Dragster

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    I have been into promods since the latter half of 1990 and have never seen anyone use anything but a three speed. I was always told that the hemi worked better if kept under load.
     
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  16. turbo69camaro

    turbo69camaro Member

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    Going off of distant memory the early IHRA days blower cars could not run billet hemi's most ran cast headed BBC style motors rules got changed to allow billet hemi's and the blower cars ran away from the nitrous cars one of the rules to slow them down was going to a three speed .A lot of guys had to run a solid shaft on the 3rd lenco unit rather than changing drive shafts,loops and shiftier mounts
     
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  17. sammy christian

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    the scotty cannon/ johnny rocca era
    4 was faster. too fast for the nitrous cars.
    also lead to the rear gear rule being 4.56 and no lower.
     
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  18. Jason Green

    Jason Green Member

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    The rule change concerning transmissions in blown pro mods came about after IHRA made billet hemis legal. And if I'm not mistaken this was when they also made a rear gear rule .it was around 98-99
     
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  19. TOL

    TOL Active Member

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    So lets say that a person had a very high strung screw motor, and planned to use that RPM range to the max. Mix of 1/4 and 1/8th mile racing. Would a 4/5/6 speed really benefit over a 3 speed? Assuming no constraints otherwise.
     
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  20. rb0804

    rb0804 Member

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    I think it depends more on if your planning on running a clutch, a converter or a lockup converter. I believe that the lockup and clutch would benefit with more gears but a converter car would be ok with three. I think the gains from the extra gears would be minimal.
     
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