Convert single-fire ignition to double-fire

Discussion in 'The Projects Forum' started by Jack_K, May 18, 2010.

  1. Jack_K

    Thread Starter Active Member

    May 13, 2009
    115
    0
    Most V-twin motorcycles utilize a single-fire ignition in which each spark plug is fired once for each complete cycle. Other motorcycles (e.g. HD) utilize a double-fire ignition where both spark plugs are fired at the same time.

    I'd like to convert a single-fire ignition to double-fire. Why? Just to see if I can do it.

    The ignition I'll be using has an Electronic Control Unit (ECU) that provides 12 volts to both coils and also, provides a path to ground to each coil individually.

    My idea is to couple each coil's ground pulse to the other coil by using diodes. I have 3 options on how to connect the diodes because I'm not sure that any of the possible methods would be harmful to the ECU.

    So, I'm asking if anyone has any knowledge or experience with this kind of idea.

    My 3 options are illustrated in the attached drawing.

    Thanks,
    Jack
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I think that you will be much better off to just leave your ignition system the way it is now.

    I can see no tangible benefit by providing spark when there is nothing to ignite.

    However, there IS a cost benefit to the manufacturer if they can make a coil with dual secondaries, rather than two coils with single secondaries.

    If you attempt what you are considering, you risk burning out your ECU by doubling it's load current.

    I suggest that you are risking a good deal with nothing to gain.
     
  3. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    The double-spark system is purely a way of saving money for the makers.

    It only needs a single timing circuit to operate a single ignition coil that has two high-voltage outputs to the plugs.

    If you have the system with individual ignition circuits, you have the better option.

    What's to gain by converting a Rolls-Royce into a Moskovich?
     
  4. Jack_K

    Thread Starter Active Member

    May 13, 2009
    115
    0
    If you attempt what you are considering, you risk burning out your ECU by doubling its load current.

    Good point. It was just a thought.

    Jack
     
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