blower boost

Discussion in 'PSI Superchargers Tech Questions' started by foxauto, Oct 21, 2005.

  1. foxauto

    foxauto New Member

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    on a current alky funny car with a hi-helix blower, what kind of boost pressures are you guys seeing at launch and through the lights???
     
    #1
    foxauto, Oct 21, 2005
  2. tafc323

    tafc323 afc

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    most people are seeing 36-42 at the hit when it rolls over, in the lights 48-52. but it also depends on where u monitor boost from the back or front of intake.
     
    #2
    tafc323, Oct 21, 2005
  3. LOTSOHP

    LOTSOHP Jr. Dragster

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    What combination? bae? 5's or 6's? CID? freshly stripped etc. all will affect boost.
     
    #3
    LOTSOHP, Oct 29, 2005
  4. Nathan Sitko - 625 TAD/TAFC

    Nathan Sitko - 625 TAD/TAFC TAD / TAFC

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    Boost

    On average we see anywhere from 37-40psi at the hit, 44-48psi at the top end at approx 9000 rpm on our TAFC.

    On one run in Seattle this year our car went 6.18 at 230mph. Launch 5300 rpm, 39psi @ 0.50 seconds (7300 rpm), 46.1psi at the stripe (8800 rpm). Littlefield 14-71 hi-helix retro fresh, BAE 5's, 526 cid, we read from the front of the manifold.
     
    #4
    Last edited: Oct 30, 2005
    Nathan Sitko - 625 TAD/TAFC, Oct 30, 2005
  5. Mike Canter

    Mike Canter Top Dragster
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    Nathan, what percent overdrive is that?
     
    #5
    Mike Canter, Oct 30, 2005
  6. Nathan Sitko - 625 TAD/TAFC

    Nathan Sitko - 625 TAD/TAFC TAD / TAFC

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    Woops, I guess that'd be an important part that I missed. 58% O.D.
     
    #6
    Nathan Sitko - 625 TAD/TAFC, Oct 30, 2005
  7. Mike Canter

    Mike Canter Top Dragster
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    Thanks. Do you or anyone else know what the difference on boost between a front manifold reading and a rear manifold reading?

    Another question is that I have been told from several racers that as the OD increases and the boost increases and the air charge temp goes up so that after a while one actually starts to lose power because of this heat. ProMods will run ODs of 50+ in the 1/8th mile because they are not running as long so the air charge doesn't get as hot. In the 1/4 mile they lessen the OD to lower the temps but then I hear from you and other TAFC racers that they always are at ODs of 50+. It confuses me.

    Has anyone out there ever measured the temperatures of the air in the manifold on a run?
     
    #7
    Mike Canter, Oct 30, 2005
  8. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    boost location

    according to a noted tuner in the alcohol ranks, he took boost in front, the rear and sides and saw no difference.

    now i have limited exp with a roots, but i've also been told as od goes up, so does the hp it takes to turn it, so at a point, you may be making more boost, but you also may be robbing more power than you would at a lower od, so the hp gained by the extra od is less than the power robbed, resulting in less hp than a lower od....

    what number that is i dont know.
     
    #8
    Will Hanna, Oct 30, 2005
  9. Nathan Sitko - 625 TAD/TAFC

    Nathan Sitko - 625 TAD/TAFC TAD / TAFC

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    We've only gone as high as 58% OD, and have been told after 60% is where it starts to hurt you. Also, we have only ever taken the reading from the front, only beacuse it's easy to get at I guess. We haven't done any temperature readings.

    I think running different blower OD's depends on your setup, perhaps the promods run higher compression than the TAFC's, I don't know. I would think though that if you went to a lower OD you would probably be able to go to a higher compression??
     
    #9
    Nathan Sitko - 625 TAD/TAFC, Oct 30, 2005
  10. Mike Canter

    Mike Canter Top Dragster
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    Ours is set up for 11.5:1. Some go to 12 and if running with the limited 29% OD they will bump it up to around 12.4.

    Will, I agree with you. Dyno testing shows that a freshly striped roots high helix at 8500 rpm requires just a tad below 600 hp to turn it. Now if I remember correctly that was around a 50% OD. A PSI only requires just under 200 HP to turn it at the same 8500 rpm.

    I guess the only true way for me to find out is to go up in OD slowly and watch the finishline MPH and graph it all out.
     
    #10
    Mike Canter, Oct 30, 2005

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