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Single coil dwell settings on MegaSquirt 2 extra.

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  • Single coil dwell settings on MegaSquirt 2 extra.

    I got the Thunderbird fired up with MegaSquirt and it starts and runs decently well until around 3,500-4,000rpm then it starts breaking up. I'm looking for some guidance for troubleshooting. I haven't had much luck interpreting answers on the MSEFI forum.

    The set up is a 3.57 board with MS2/extra 3.30b. Tach input signal is off the pertronix unit, and Pin#36 output goes right to the negative side of the coil (my CDI box was a bust). I have timing set fixed to zero because the vacuum and mechanical advance systems are in full operation.

    Cranking Dwell (ms): 6.5
    Dwell Type: Standard Dwell
    Maximum Dwell Duration (ms): 2.5 -I've had this up to 3.5
    Acceleration Compensation(ms): 1
    Maximum Spark Duration (ms): 0.1 - I've had this up to 5
    Over and under dwell protection are both turned on.

    The Tach signal is rock solid until it starts breaking up above 3,500 rpm, and I can't tell if it's the VR pots or if it's dwell/coil setting limited. Or if it's my timing settings interfering with the mechanical/vacuum advance systems. What should I be checking?
    Escaped on a technicality.

  • #2

    Re: Single coil dwell settings on MegaSquirt 2 extra.

    I'm wondering about the Pertronix since your breakup rpm is where they claim the greatest gains. Is it getting noisy there?
    .

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    • #3

      Re: Single coil dwell settings on MegaSquirt 2 extra.

      I'm suspecting the coil itself......they fail in strange ways at times.....
      http://i6.photobucket.com/albums/y21...ilverlake4.jpg

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      • #4

        Re: Single coil dwell settings on MegaSquirt 2 extra.

        I'm wondering about the Pertronix since your breakup rpm is where they claim the greatest gains. Is it getting noisy there?
        My concern about the Pertronix is that it's signal might not be as straight forward to the MegaSquirt as a normal hall sensor would be because it calculates it's own dwell, and might be feeding the MS a signal with an 'adjusted' timing. But I set the input at 'Rising Edge' figuring that would work fine, but that really is no guarentee that the pertronix isn't delaying the signal, aka start of charging time, to control dwell. And if that is happening then the pertronix delays the charge time a bit, then the MegaSquirt does it again, and suddenly there isn't enough dwell time for higher rpm. I have a set of points I could try out as the trigger mechanism too.

        If I had a couple weeks to play with it I'd simply test out a few theories, but I'm hoping to drive this thing out of state Wednesday night and don't have the time available after work. So I'm looking to fast track it

        I'm not suspecting the coil until I'm very confident my set up is correct and it still has problems. When I was letting the pertronix do it's thing and the megasquirt simply got the signal from the negative terminal of the coil (last week) it rev'd just fine to 5,000 grand. The signal was just a bit more noisy than I liked because the tach signal source.
        Escaped on a technicality.

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        • #5

          Re: Single coil dwell settings on MegaSquirt 2 extra.

          Randal, post a pic of a datalog at the point of breakup. What does your tach signal do? I'm betting you have electrical noise getting into your tach input and it's causing the MS to lose sync with the engine.
          Proudly using www.DIYAutotune.com custom EFI components!

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          • #6

            Re: Single coil dwell settings on MegaSquirt 2 extra.

            If you suspect the pertronix is making it's own adjustments - can you dial back all the MS adjustments to zero?
            There's always something new to learn.

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            • #7

              Re: Single coil dwell settings on MegaSquirt 2 extra.

              Randal, post a pic of a datalog at the point of breakup. What does your tach signal do? I'm betting you have electrical noise getting into your tach input and it's causing the MS to lose sync with the engine.
              I did datalog it and I'll send it to you at some point in the next week. I got the T-bird running good now with no MS coil control (back to coil negative trigger), and I'm heading out of town as soon as I get home from work. It behaved a lot like an MSD box ignition cut. Hit 3500rpm and would break up, if I kept pouring on the throttle it'd occassionally get to 4,000rpm, but it didn't seem to be spiking to anything radical or dropping way out. The datalog would show for sure though.

              If you suspect the pertronix is making it's own adjustments - can you dial back all the MS adjustments to zero?
              Because I don't have the mechanical advance locked out I had the MegaSquirt set to a fixed timing. I tried 0* advanced and 1* advanced incase it needed a number greater than zero.
              Escaped on a technicality.

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