Start Retard with Grid and 20 Amp Mag

Discussion in 'PSI Superchargers Tech Questions' started by Insane_Crew, Jun 19, 2017.

  1. Insane_Crew

    Insane_Crew New Member

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    Done some searcing/ lurking and can't find an answer so I'll ask. We very recently switched our top sportsman program to blown alcohol and would like to be able to run some start retard to help out our block mounted starter. Details of the combination are as follows: BBC 555 with Brodix BB3 heads 13.5 compression, TBS 14.71 HH center discharge 8% over making 13 pounds boost. BAU injector. We are running a grid/ MSD 3/8" crank trigger/ 20 amp mag and promag box. Total timing 34 degrees. When I enter a start retard into the engine RPM screen of MSD view we get a no spark, no start condition. Take away the retard and it fires right up. Is it possible I need to back the Mag phasing up? We also run 7* launch retard and it works just fine.

    Thanks
    Brad
     
    #1
    Insane_Crew, Jun 19, 2017
  2. Mike Canter

    Mike Canter Top Dragster
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    Most likely that is the problem. The spark is weak at starter rpm. Try changing your rotor phasing so it matches your start retard timing and see if it starts
     
    #2
    Mike Canter, Jun 19, 2017
  3. Insane_Crew

    Insane_Crew New Member

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    Thanks Mike, will spin the mag back and try it. I suppose if it starts then we could try splitting the difference to hedge against spark scatter at higher RPM.
     
    #3
    Insane_Crew, Jun 19, 2017
  4. Insane_Crew

    Insane_Crew New Member

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    Checked with MSD and we were told that you can't use start retard with the mag.
     
    #4
    Insane_Crew, Jun 26, 2017
  5. Mike Canter

    Mike Canter Top Dragster
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    Have in the past. It works if the rotor phasing is off to compensate for it
     
    #5
    Mike Canter, Jun 27, 2017
  6. Insane_Crew

    Insane_Crew New Member

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    Thanks again Mike, how much were you pulling if you don't mind?
     
    #6
    Insane_Crew, Jun 28, 2017
  7. Mike Canter

    Mike Canter Top Dragster
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    You should need more than 5 degrees. On our current motor we don't pull out any. Just spin it over for a two count and hit the ignition. Never kicks back and always starts
     
    #7
    Mike Canter, Jun 28, 2017
  8. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Another option may be to either run a changeover switch or the Leahy start/relay switch.

    The changeover switch is just a manual switch to change from mag to grid/trigger. Many teams with flywheel starters will do this to start on the mag, then switch it over to trigger to run. This way you can run your mag at optimal phasing for the run, not just starting.

    Leahy also sells a start relay which switches it to mag while the starter button is depressed, then automatically resets to trigger it after starter released.

    I think the switch is like $55, the relay is $205. Depends on if you want to have someone switch it over or have it automatically done.
     
    #8
    Will Hanna, Jun 28, 2017
  9. Insane_Crew

    Insane_Crew New Member

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    Thanks for the great information fellows. We are quite new to the blown combination and learning every day.
     
    #9
    Insane_Crew, Jun 28, 2017

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