Setting start time of run on computer

Discussion in 'PSI Superchargers Tech Questions' started by Blown Altered, May 24, 2013.

  1. Blown Altered

    Blown Altered New Member

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    I have heard different ideas and thoughts on picking the starting point of a run on the computer. What is everybody doing here and why. Driveline rpm, g-force, fuel pressure etc...
     
    #1
    Blown Altered, May 24, 2013
  2. rb0804

    rb0804 Active Member

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    I use when the driveshaft rpm starts to pick up but this can become a little tricky if the air gap on the clutch is a little tight and the car is pulling through the lights. We don't run a g meter. Curious to see what others do, it doesn't really matter as long as you do it the same everytime. Now if you are having someone help you and they are stating that you need x amount of driveshaft speed y into the run, then it makes a difference, you will need to know how they set their start time.
     
    #2
    rb0804, May 25, 2013
  3. underby6

    underby6 Active Member

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    Zeroing the car off of the g-meter is how I choose to do it. I actually zoom in on it and make it precise. If you're tuning the car and are off on the start time, trying to judge leanouts/timers etc. is nearly a futile effort.

    Brandon Booher
    NHRA TAD #323
    Torque MGMT. - Owner
     
    #3
    underby6, May 25, 2013
  4. KJC

    KJC Authorized Merchant

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    I set start time off the blower
     
    #4
    KJC, May 25, 2013
  5. Andy C

    Andy C Member

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    Start

    Race pack makes a 12v switch you can wire to trans brk or Clutch, you will be accurate all the time, I was not alot of $$$.
     
    #5
    Andy C, May 25, 2013
  6. Mike Canter

    Mike Canter Top Dragster
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    As been already said. It depends on your car or what you are looking for or what you are referencing. If you are doing just driveshaft rpm then the start of the driveshaft is good BUT be careful that the data you are comparing it to is measured the same way. If I say your driveshaft rpm should be 2600 at .5 seconds then make sure that I measured it from the driveshaft start. If you are more interested in fuel timers then a clutch switch to the Racepak or off the fuel pressure rise is good. With G's there can be a slight delay between the fuel pressure rise and the change in G's. it is not much but it is there. It is up to you and want you want to measure. I bet there are four or five different start points you can use.
     
    #6
    Mike Canter, May 25, 2013
  7. Mark Leigh

    Mark Leigh Member

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    I always use the first point where the fuel pressure drops as a start point---- it seems to get everything involved that comes after that-------------this is with a glide clutch, blown nitro setup.
     
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    Last edited: May 26, 2013
    Mark Leigh, May 25, 2013
  8. Cpt Kludge

    Cpt Kludge Member

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    We use a throttle position sensor (TPS) wired into one of the analog channels on our computer. It's a GM OEM part so it's inexpensive. It's easy to mark the start time and also shows if the driver is pedaling the car down track.

    Steve
     
    #8
    Cpt Kludge, May 27, 2013
  9. jody stroud

    jody stroud ZOMBIE Top Dragster

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    I have a toggle switch in my cockpit that I hit after I prestage. Catches the boost and egts while on the two step. Shows the whole run with no problems.
     
    #9
    jody stroud, May 28, 2013
  10. JustinatAce

    JustinatAce Member

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    As long as you use the same reference point every time, be it driveshaft or where the boost goes up, Fuel Flow opens up, or G-meter, it really doesn't matter.. Just be consistent about where you set "0".
     
    #10
    JustinatAce, May 28, 2013

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