Slow mph and rpm curve is near flat after hi gear shift Blown Hemi Pro Mod

Discussion in 'PSI Superchargers Tech Questions' started by kbhemi, Aug 30, 2016.

  1. kbhemi

    kbhemi Member

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    OK this thing is killing me - 5.14 gear - 1/8th mile - veney alcohol headed hemi - 3 speed lenco - WITH A CLUTCH - 2470 lbs - 526 ci - Kobelco superman - ran 4.17 at 173mph - but when I shift into high gear at 9000 - it just lays down - launch at 5400 seems a little slow to 8700 but okay - rpm drops to 8000 and is quick to rev to 9000 rpm high gear shift - it then drops to 8000 and sinks to 7850 - its a pig it barely gets to 8150 through the lights. Is it lean - rich - to much timing to little?? Last year ran 179.6 mph at 8600 - only change was to a JBR 2016 carbon hat - but I dont think thats a problem. Am running 40 over pulleys - help!! I thought I saw Bruce Mullins looking to help - cant find the number! kbhemi@cox.net
     
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  2. jay70cuda

    jay70cuda Well-Known Member

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    Wow. Need some info to help out. Fuel flow at launch ,8000, driveshaft speeds at .250,500,1.00 ? Could be a lot of smal things. Like who set the fuel system up?
    Clutch slipping too much or welded up tight?
    Motor is pig rich ?
    Boost and fuel flow at 6000,7000,8000,9000
     
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  3. gordon tarbell

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    With fresh set of plugs what do they look like?
     
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  4. Mike Canter

    Mike Canter Top Dragster
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    you may want to consider that the 40% overdrive is too much for a superman blower. Superman blowers are designed to be more efficient at lower over drives. On your Racepac watch the boost in each gear and see if it gets to a rpm where the boost starts dropping. Is this an unmodified superman? You might try dropping it back to a 35% OD and see what happens
     
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  5. drew556

    drew556 Member

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    Mike the superman has been modified by dmpe for high overdrive although 40 may still be a little much looking at the racepak never drops boost even on the shift gets to 36-37 lbs pretty quick then will slowly creep up to 38-39 lbs by the end of the run going by your numbers in another post .33-.34 Gpm per pound of boost at 38 lbs of boost flow is about 15.5 so if I did the math right should be about 12.25 which tells me it's way fat I know the pump we have is a waterman that cam of a screw blow top alcohol dragster and believe the flow is 19.25 so it's way to big for us I'll try to get some other info by the way I'm kbhemis son been doing this with dad for 20 years so if he can't figure out the computer and how to get you some info I'll post it up
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    I would say it was real fat from your figures. What do a new set of plugs look like after one run? Being that fat would explain all your symptoms. If your pump is way to big and you have an electric timed fuel bypass you are not using then you can put a jet in that and open it on the hit to get rid of the extra fuel or put a bigger pump loop jet in.
     
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  7. kbhemi

    kbhemi Member

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    Here is some more info
    Fuel flow at launch & 8000 (9.00 &13.09)
    Driveshaft speeds at .250,500,1.00 (1301, 2157, 2811, 3181)
    Who set the fuel system up - that would be me.
    Clutch slipping too much or welded up tight - clutch seems good maybe a little tight at shift rpm - drops 800 on 1-2 and 1000 on 2-3 - but I believe thats due to lack of hp.
    Motor is pig rich - according to some calculations I have seen boost vs fuel - yes - looking at my plugs white clean and the electrode only discolored - it is on the safe side - pig rich I dont know.
    Boost and fuel flow at 6000,7000,8000,9000 (31-9.84, 35.7-11.54, 36.9-13.27, 37.6-14.65)
     
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  8. DQUES

    DQUES Member

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    14.65 gpm at 9k is way rich on that combo and boost level .
     
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  9. Mike Canter

    Mike Canter Top Dragster
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    how are your fuel bypasses set up right now. Are this fuel and boost figures all in first gear or what? If you are going to lean it out then you will probably need more finger weight because of the increase in power
     
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    Last edited: Aug 31, 2016
  10. promodracer

    promodracer Member

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    Sounds fat
     
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  11. kbhemi

    kbhemi Member

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    how are your fuel bypasses set up right now.
    (pump sizer .070 and 25 psi - 2 step .075 with clutch in and 3000 to 5800 rpm - electrimotion .060 at .01 to 3.80 and .033 at 1.50 to 4.20 main .085)
    Are this fuel and boost figures all in first gear or what?
    fuel and boost in low gear except the 9000 thats in 2nd - 3rd never gets above 8150)
    If you are going to lean it out then you will probably need more finger weight because of the increase in power.
    (I sure hope so)
     
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  12. Mike Canter

    Mike Canter Top Dragster
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    Roughly computing in my head the fuel looks pretty good below 8000 rpm so just as a guess I would change that second leanout from a 33 to a 65 and see how it runs and how the plugs look.
     
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