Instant center

Discussion in 'PSI Superchargers Tech Questions' started by wilman0069, Sep 9, 2009.

  1. wilman0069

    wilman0069 New Member

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    Help, can't get blown alcohol door stuck to the ground, need a good instant center to start with. 565 ci w/ 14/71. 2500# race ready w/ driver. 56% on front. 4.30 pro gears w/ BTE glide. Launching from 3-4900 rpm's same story every time, comes up on wheelie bars, blows tires off and falls flat on face.
     
    #1
    wilman0069, Sep 9, 2009
  2. JRB

    JRB Guest

    Thats a pretty significant amount of nose weight. 56%? Can you move some around or are you stuck at the current configuration?
     
    #2
    JRB, Sep 9, 2009
  3. JustinatAce

    JustinatAce Member

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    What tranny ratios are you running?
     
    #3
    JustinatAce, Sep 10, 2009
  4. B.DOUCET

    B.DOUCET New Member

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    With a convertor and 44% on the rear might be a tuff job. Not sure what gear ratio's are avalible for a glide, but 1st gear ratio and timing control would be my best guess to get it to leave. On the four link, I would start around 50" and 7".
     
    #4
    B.DOUCET, Sep 10, 2009
  5. Mike Canter

    Mike Canter Top Dragster
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    I agree with the 50" 7". That is a good starting point. The other problem might be your rear shocks. Either the valving is not heavy enough for a blown car such as stock Koni SPA1 shocks or they are not adjusted correctly especially on the rebound (extension side) which is what plants the tires. What shocks do you have and how are they adjusted? Also what is the spring rate of the rear springs?

    Do you have any type of timing control that will let you pull timing at the release of the transbrake button and rampit back in?
     
    #5
    Mike Canter, Sep 10, 2009
  6. Outlaw68

    Outlaw68 Member

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    I run my true 10.5 car at 56%, you need some timing control for sure, and you said the car gets on the bars then falls on its face, most over look so many things involved in these cars. The shock rate up front, the amount of travel, crankshaft centerline, and of course as pointed out the rear shock. I run lamb coil overs with a heavy valving for promod cars.

    One thing to consider is HOW hard its striking the wheelie bars, the length of the bar and how quick it gets on them. I run a 14/71 K8 HH on a 509 @ 3400 lbs, and its been tough and Im learning all the time. Another HUGE area is convertor. Do you have any video of the car from the rear we could watch?

    It may be a combination of things, but assuming this car went down the track good prior to your new found hp and tq, it may be as simple as a few changes.
    This is one of my favorite subjects and I feel we can all learn from it. Give us some video, and some details on what your doing I bet we can get it sorted out...
     
    #6
    Outlaw68, Sep 10, 2009
  7. Flyboy68

    Flyboy68 Member

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    Excuse my ignorance, but does that mean the instant center needs to be 50" in front of the rear axle's and 7" up from the ground? or relative to the camshaft/cg line?

    Josh
     
    #7
    Flyboy68, Sep 10, 2009
  8. Mike Canter

    Mike Canter Top Dragster
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    The point from the center of the rear axle that is 50" out and 7" up from the ground. If you extended the upper and lower 4 link bars until the crossed at that point is the IC. Imagine that IC is where you grip the handle of a breaker bar that is attached to the rear axle shaft and by changing the point at which you grip the bar changes the leverage applied in reverse from the rear axle rotation to the frame of the car. Did that confuse the issue?
     
    #8
    Mike Canter, Sep 10, 2009
  9. Flyboy68

    Flyboy68 Member

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    Yeah that makes since. I understand what the IC is, just didn't know from what point those measurments were from. So is that 7" from the ground or from the imaginary line going from the rear axle centerline and running parallel w/ the ground?

    Josh
     
    #9
    Flyboy68, Sep 10, 2009
  10. Flyboy68

    Flyboy68 Member

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    Nevermind i can't read...lol
     
    #10
    Flyboy68, Sep 10, 2009
  11. Money Shot

    Money Shot Member

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    I feel your pain Wilma. I have to footbrake my junk just to get it down the track.
     
    #11
    Money Shot, Sep 10, 2009

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