BBC/glide/ screw blower vs roots set up?

Discussion in 'PSI Superchargers Tech Questions' started by DISCODEAN, Dec 31, 2007.

  1. bob szabo

    bob szabo FC / altered

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    care with converter size

    I watched a screw blower bracket car with a clutch this last year. Memory recalls it was a D rotor at about 85%.
    PROBLEM ONE: He started out with his launch at low RPM, below 5000. The car ran OK but not great. Then he raised the launch RPM and the car picked up a bunch, (many tenths). If a screw blower is mated to a tight converter that keeps the R's down in the launch (especially with the 2 speed glide), and a lower overdrive, the launch power may be down.
    PROBLEM TWO: Then there is the added weight which is not helpful on a marginal track.
    PROBLEM THREE: The reference car was also very ET sensitive to launch RPM. ETs varied quite a bit throughout a day's performance by several tenths. Launch RPM appeared to be pedal controlled which is a variable. But I have not experienced that kind of variation with our Roots / clutch setup, and I have not seen other cars with Roots setups or screw setups with high RPM launch vary that much.
    Although only a sample size of one in the pie, it is another spice in the recipe.
    bob szabo, author of racing manuals: Fuel Injection Racing Secrets & 5000 Horsepower on Methanol
    bob@racecarbook.com
     
    #21
  2. DISCODEAN

    DISCODEAN Member

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    thanx 4 the input bob

    Bob I met you at Rockingham,2 yrs ago,I was driving a blown HEMI,purple spitzer with the barn door injection, and a/fuel hat..remember? you took some pix yada..yada... what kind of numbers were they putting down? thanx disco dean
     
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  3. BUTCH

    BUTCH Member

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    BBC,Glide , and a 206D

    DiscoDean
    I have a 500 inch BBC, I put a PSI set up on a few years ago in a R.E.D, I have been running a shorty glide from Mikes Trans, we run it mostly at 60% over, and have all the power we can us, our set up has been saving me a lot in parts, the combo runs very easy, and our 60 foot times are killer best .932, we us a 2 step to control the launch rpm and a air control cylinder off the trans brake to control the butterflys at the launch rpm, we never hit it harder then 3600 rpm's, If you need some info give me a call on the cell 707 974 3185 , e mail at SPMI@SOIC.NET, or P.M. GOOD LUCK
     
    #23
  4. TOL

    TOL Active Member

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    It would just clutter your shelf space, and we wouldn't want that to happen would we ?..... :).......
     
    #24
  5. DISCODEAN

    DISCODEAN Member

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    good clutter is better than no clutter at all !!! espically if its a screw!! hopefully the rules will change soon anyway . but to me it is legal!
     
    #25
  6. bob szabo

    bob szabo FC / altered

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    performance answer

    mid to hi 6's before raising the launch RPM then mid to low 6's immediately after. the owner / driver was surprised but happy.
    Bob Szabo, author
    www.racecarbook.com
     
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  7. DISCODEAN

    DISCODEAN Member

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    thanx bob

    Thanx bob 4 the reply!! DiscoDean
     
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