roots vs d rotor screw

Discussion in 'PSI Superchargers Tech Questions' started by Full Tilt, Oct 23, 2019.

  1. Full Tilt

    Full Tilt Member

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    running a older littlefield 14/71 front discharge at 40% over on 521 hemi , 42 psi, could we run the screw at lthe same overdrive and have same or more boost. screw is still in cert . tring to free up some hp
     
    #1
    Full Tilt, Oct 23, 2019
  2. kosky racing

    kosky racing Comp Eliminator

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    not at same rpm you would need about1.92 over to get about 42to44 boost
     
    #2
    kosky racing, Oct 23, 2019
  3. Mike Canter

    Mike Canter Top Dragster
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    I agree with Mik e but you need far less horsepower to turn the D rotor than the roots blower so horsepower is gained there. Also there are no strips in the D rotor screw blower to wear out so it maintains a more stable boost number so you are not having to change the fuel tuneup all the time.
     
    #3
    Mike Canter, Oct 24, 2019
  4. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    You will gain 300-400 hp at the same boost going from an older roots to the screw. 1.92 (some would say 92 over) would get you around 40 - 42 lbs depending on how good the blower is, camshaft and some other things. I would recommend getting someone to set you up a fuel system. Learning curve costs money. Runs down the track and potential problems. Getting a fuel system flowed drastically speeds up that learning curve with a proven baseline and knowing everything is set up as it should on the bench.
     
    #4
    Will Hanna, Oct 24, 2019
    Mike Canter likes this.
  5. Full Tilt

    Full Tilt Member

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    thanks mike and will, this screw has strips in the rotors , the rotor has a width around .580 plus. im assuming its a d . i agree with the bench tuneup, too much time and money to spray pistons out the exhaust lol.
     
    #5
    Full Tilt, Oct 24, 2019
  6. Full Tilt

    Full Tilt Member

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    thanks ,was not sure about the overdrive difference
     
    #6
    Full Tilt, Oct 24, 2019
  7. Mike Canter

    Mike Canter Top Dragster
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    The strips do not make contact with the case or the other screw so they don’t wear.
     
    #7
    Mike Canter, Oct 24, 2019
  8. Full Tilt

    Full Tilt Member

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    ok i did not know that, thanks mike
     
    #8
    Full Tilt, Oct 25, 2019
  9. kosky racing

    kosky racing Comp Eliminator

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    They are not supposed to touch -some people try to make them seal -they can get ugly from there
     
    #9
    kosky racing, Oct 25, 2019
  10. rb0804

    rb0804 Active Member

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    What’s the purpose of the strips if they don’t touch anything?
     
    #10
    rb0804, Oct 25, 2019
  11. Mike Canter

    Mike Canter Top Dragster
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    There is a specific clearance required on these stripes making them as close as possible without touching. When they blueprint a screw blower they coat the screws to get the right clearance. If the screws touch then the blower is ruined.
     
    #11
    Mike Canter, Oct 25, 2019
  12. kosky racing

    kosky racing Comp Eliminator

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    My rotors touch on the outlet side-told not a problem
     
    #12
    kosky racing, Oct 26, 2019
  13. TOL

    TOL Active Member

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    Have they rubbed away the surface coating and/or started to gall against each other? Do you run all your hat fuel thru the 4 holes in the PSI case, or have you split it up to run more percentage to the rear of the opening?
     
    #13
    TOL, Oct 26, 2019
  14. kosky racing

    kosky racing Comp Eliminator

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    got 5 aireated most over80s
     
    #14
    kosky racing, Oct 26, 2019
  15. Mike Canter

    Mike Canter Top Dragster
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    According to Norm Drazy it should be close but not making contact.
     
    #15
    Mike Canter, Oct 26, 2019
  16. kosky racing

    kosky racing Comp Eliminator

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    That is correct Mike tell that to the mfg.
     
    #16
    kosky racing, Oct 26, 2019
  17. SpeedDemon

    SpeedDemon New Member

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    I have a 206 b that has two worn stripes down the center of the male rotor from the strip of the female. Not having any experience with screws, I figured this was probably normal. Now having read this, should I be concerned running this blower? What does coating do or prevent?
    Thanks
     
    #17
    SpeedDemon, Oct 26, 2019
  18. SpeedDemon

    SpeedDemon New Member

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    Sorry about taking op’s thread, I realize I probably should of started another since this is a completely different topic
     
    #18
    SpeedDemon, Oct 26, 2019
  19. bwpracer

    bwpracer Member

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    Do you have an interest in selling that B blower ?
     
    #19
    bwpracer, Nov 26, 2019
  20. SpeedDemon

    SpeedDemon New Member

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    No interest in selling mine, but I saw one for sale on race junk the other day...
     
    #20
    SpeedDemon, Nov 27, 2019

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