Hi Helix Over Drive

Discussion in 'PSI Superchargers Tech Questions' started by lugnut, Aug 22, 2019.

  1. lugnut

    lugnut Member

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    Whats your guys thoughts on over driving a 14-71 Littlefield over 58%? Its just a retro case with K11 rotors in it. We have a friend of ours that runs a mud truck that has a lot of his competitors telling him they are running theirs around 80%
    Theyre running a 200' pit and usually are just over 2seconds of wide open throttle...
     
    #1
    lugnut, Aug 22, 2019
  2. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Need to work backwards from peak rotor speed. So if you are turning 8000 in 2000', at 1.58, the rotors are already going 12640. 12-13k is a common max rotor speed recommended for modern era hi-helix retros. 12,000/1.80 = 6667 rpm. So at 7000 they are at 12,600.

    The other thing you run into with the higher OD is the blower is turning much faster obviously than what a conventional fuel system is designed for so you are going to need to really increase the hat area to keep the rotors cool. That means more percentage through the top, so your distribution is going to suffer.

    I would call out to Littlefield to discuss.
     
    #2
    Will Hanna, Aug 22, 2019
  3. lugnut

    lugnut Member

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    Thanks Will, I had never heard anyone turning one that hard before so just wanted to check... Figured Andy would see this at some point and give his opinion as well...
     
    #3
    lugnut, Aug 22, 2019
  4. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    the other thing to keep in mind is at some point the hp to turn it is more than the hp gained from any extra boost.
     
    #4
    Will Hanna, Aug 22, 2019
  5. Mike Canter

    Mike Canter Top Dragster
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    To add to Will. The extra HP and heat generated which heats up the incoming air charge which raises the DA and causes power loss. If you get a look at a Racepak run of one of these guys running super high OD then watch the boost curve and see if it rolls over at some engine rpm. If it does then that should tell you something
     
    #5
    Mike Canter, Aug 22, 2019
  6. lugnut

    lugnut Member

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    I’ve also heard over the years that some point your just spinning it harder with no additional boost, not like a screw that makes boost.
     
    #6
    lugnut, Aug 23, 2019
  7. andy wilfong

    andy wilfong Active Member

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    2 factors to consider, even if you do spin it that fast, and increase the boost , parasitic loss and manifold temp will kill the power, boost isn’t always power,
     
    #7
    andy wilfong, Aug 23, 2019
    promodracer, bandit496 and Mike Canter like this.

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