Another Grid timing question

Discussion in 'PSI Superchargers Tech Questions' started by Big Steve, Mar 11, 2019.

  1. Big Steve

    Big Steve Member

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    Blown BBC TD application. Using a small crab distributor cap how much timing do you think can be pulled before I start having cross fire or other issues due to rotor phase. Went 3.87 this weekend, base timing at 28*, pulling 6* with 4* back in by 1 sec. that 87 equates to about a 5.94 or so. Need to find a curve that works to slow to the 6.10 index for Houston in 2 weeks
     
    #1
    Big Steve, Mar 11, 2019
  2. Critical Mass

    Critical Mass Member

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    Big Steve,
    You could try taking out a 0.1 at a time from 4.0 deg. until you get to your 6.10 index.
     
    #2
    Critical Mass, Mar 11, 2019
  3. Mike Canter

    Mike Canter Top Dragster
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    Well, 360* divided by 8 is 45*. So you have 45* between posts so if you divide that by 2 then the middle crossover Point is 22.5* max theoretical degrees before you have cross fire but you never want to push it that much. If you have a fouled plug or a bad plug wire that the spark has a hard time going down then it will find another path. If all is in great shape then I would say you are safe pulling out up to 8-9* with no problem. Your plugs need to be gapped at .015-.016” to make it easy for the spark to jump when the cylinder has high pressure and lots of alcohol in it. You didn’t say if you were using a crank trigger or not.
     
    #3
    Mike Canter, Mar 11, 2019
  4. Bjs344

    Bjs344 Member

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    Typically I’m phased around 24, base timing at 28-31. I’ve gone down as low as 13 or maybe 12 degrees for a couple ticks (11-12 degrees out of phase). Had a friend that went 14 out of phase and claimed that’s when it started cross firing. These were crab cap crank trigger distributors.
     
    #4
    Bjs344, Mar 11, 2019
  5. Mike Canter

    Mike Canter Top Dragster
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    Yes with a crank trigger and moving the rotor phasing like you have done you have added safet and can safely add another 4*. Wouldn’t go any further than that.
     
    #5
    Mike Canter, Mar 11, 2019
  6. Big Steve

    Big Steve Member

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    My big concern was with the crab cap because it is so small. Yea I have a crank trigger. I know someone who knock 15* out this past weekend but only for .400 and brought it all back in by 2 secs but he has a large cap. It was a procharger car and I would of thought it would cross fire but didnt and made a good pass
     
    #6
    Big Steve, Mar 12, 2019
  7. caseyspradlin

    caseyspradlin Member

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    i have successfully pulled 12 with this distributor set up
     
    #7
    caseyspradlin, Mar 20, 2019
  8. Krister johansson

    Krister johansson New Member

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    45? It is 90 "crank" degrees between cap terminal.
    My tow cent from Sweden...
     
    #8
    Krister johansson, Mar 21, 2019
  9. Krister johansson

    Krister johansson New Member

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    My Two cent....
     
    #9
    Krister johansson, Mar 24, 2019
  10. Big Steve

    Big Steve Member

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    With base timing is 28*. I phased the rotor and 23* and pulled 15* last weekend without any problems. Map had all the timing in around 2.2 secs and it still wanted to run well under the index even with some fuel system issues and other issues. Ended up spot dropping, qualified #4 and went a few rounds so not a bad weekend
     
    #10
    Big Steve, Mar 28, 2019
    Mike Canter likes this.

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