Wheel speed graph

Discussion in 'PSI Superchargers Tech Questions' started by 32 bantam, Jun 20, 2016.

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  1. 32 bantam

    32 bantam Member

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    I have a RPM data recorder. I'm trying to learn more on what I'm seeing .....to what the car is doing. 511 Arias supercharged 7.0 altered car. My question is wheel speed.......at the shift (1.61 into the run) the drive shaft RPM is 4268 @ 1.71 it is 3634. My take on this is the wheel speed is too high in 1st gear and the shift lets it "bite" . The car is still pulling thru this...I don't feel it slow down ...like the wheel speed says.
    Am I one the right track?????
     
    #1
    32 bantam, Jun 20, 2016
  2. Mike Canter

    Mike Canter Top Dragster
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    If I might suggest. If you want answers then they need to know rear gear and tire diameter. Also most everyone gives wheel speed at .2 secs, .5 secs, .75, 1.00, 1.25 and so on. So if you give all that then somebody may give you an answer.
     
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    Mike Canter, Jun 20, 2016
  3. 32 bantam

    32 bantam Member

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    Thanks Mike....here it is...
    Tire dia. 33.5...3.89 rear gear. Powerglide 1.6 1st gear
    .2 1254
    .5 1741
    .75 2025
    1.0 2483
    1.25 2925
    1.5 3890
    1.64 (shift) 4268
    1.75 3617
    2.00 3871
    2.25 4162
    2.50 4447
    2.75 4763
    3.00 4922

    There is a 651 driveshaft RPM loss at the shift. Is this because the tire is "slipping" all thru 1st gear and then hooking up after the shift?
     
    #3
    32 bantam, Jun 20, 2016
  4. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    While anything is possible, I highly, highly, highly doubt you are spinning the tire for 1.64 seconds given your gearing.

    Can you post a screen shot of the run you are describing?

    Is it shaking before the shift? There is a pretty good gain in wheelspeed from 1.25 to 1.5, so it looks like it is breaking the tire loose then maybe hooking up after the shift.
     
    #4
    Will Hanna, Jun 20, 2016
  5. 32 bantam

    32 bantam Member

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    I failed to get the file on here correctly......it put a file on here that had access to my whole computer!!!! ...so I deleted it. I will need to get help from Paul Francia.......
    thanks
     
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    32 bantam, Jun 20, 2016
  6. 32 bantam

    32 bantam Member

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    Paul Francia stopped by and looked at the graph.....he says it looks like a voltage problem...maybe a weak ground or bad on/off switch causing the spikes and the really big one at the shift because I use an electric solenoid to move the shifter. My plan is to go over all the wiring and replace the switch.
     
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    32 bantam, Jun 20, 2016
  7. Mike Canter

    Mike Canter Top Dragster
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    What is the data logger voltage reading during the run especially during the shift. Where are you seeing this spikes? Are the on the engine graph line or the DS graph line?
     
    #7
    Mike Canter, Jun 21, 2016
  8. 32 bantam

    32 bantam Member

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    16 volt battery reading 16.6...during the run 16.3 to 16.6, except at the shift spike in the DS graph. I use an electric solenoid to shift.
    @ DS spike peak voltage is 15.47....@ the bottom of the spikes it is 16.61 and 16.46. The spike lasts from 1.50 to 1.75
     
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    32 bantam, Jun 21, 2016
  9. 32 bantam

    32 bantam Member

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    The engine speed graph line RPM drop, at the shift, matches the position of the DS spike.
     
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    32 bantam, Jun 21, 2016
  10. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    bantam graph.jpg
    Here is his graph he sent me.

    I initially questioned the voltage spike theory, but the more I looked at it, there would be a corresponding spike in engine rpm with that much 'spin.' Not to mention if that was a real DS spike it would either shake his brains out or try to swap lanes spinning that hard down track.

    I tend to agree with some sort of interference causing a false DS reading. Randy at RPM may be able to clarify this.
     
    #10
    Will Hanna, Jun 21, 2016
  11. MaineAlkyFan

    MaineAlkyFan Active Member

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    The fact that the DS, RPM & G all correlate make me think any anomaly is system wide. Those are three different system inputs, one of which is on board in the recorder. Given the voltage drop is fairly minor and also correlates with the solenoid load I don't think there was a momentary open or short, especially only losing 1V over .25 sec. The only thing I can't come to terms with is not feeling the drop in the car. Do you have a comparative graph of another run?

    Chris Saulnier Team Tigges
    Mechanic Falls, Maine
     
    #11
    MaineAlkyFan, Jun 21, 2016
  12. kosky racing

    kosky racing Comp Eliminator

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    kosky racing, Jun 21, 2016
  13. kosky racing

    kosky racing Comp Eliminator

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    Its a spike in the dr is caused by the solenoid acting as a condenser the same thing happens with the grid when ussing nitrous activated by a solenoid there is a feedback using the msd battery surpressor on the power line will usually make this problem go away [the big red one].
     
    #13
    Last edited: Jun 21, 2016
    kosky racing, Jun 21, 2016
  14. 32 bantam

    32 bantam Member

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    I do have another graph and laid over this one in almost matches perfectly. I have a few graphs actually...and they all mtach pretty close.
    I like the "solenoid acting as a condeser" theory.
    It would be an easy fix to add the MSD suppressor.
     
    #14
    32 bantam, Jun 21, 2016
  15. Mike Canter

    Mike Canter Top Dragster
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    Mike Kosky is 100% correct. We saw spikes when our fuel lean outs turned on and off when looking at the recorded Grid voltage. Installed the big red MSC capacitor and it all went away.
     
    #15
    Mike Canter, Jun 21, 2016
  16. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Mike Kosky knows because he has nitrous solenoids and a grid on his riding lawn mower!!!
     
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    Will Hanna, Jun 21, 2016
    MaineAlkyFan likes this.
  17. kosky racing

    kosky racing Comp Eliminator

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    I am sorry Will I forgot to tell you about my nitrous education about the time you were born!
     
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    kosky racing, Jun 21, 2016
    Will Hanna likes this.
  18. BEDNAR1320

    BEDNAR1320 Member

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    I also have an RPM logger, I have no weird DS speeds, it rises smoothly throughout the run. I do have an electric shifter (B&M) also. I do use an MSD suppressor on the power supply for everything.
     
    #18
    BEDNAR1320, Jun 22, 2016
  19. 32 bantam

    32 bantam Member

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    Does anybody know the MSD Capacitor value?
    My data recorder is wired directly to the battery. Do I install the capacitor in the line...or the feed wire to the shifter?
     
    #19
    32 bantam, Jun 25, 2016
  20. Blownalky

    Blownalky Top Sportsman

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    #20
    Blownalky, Jun 25, 2016
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