How does the CDI know when to fire spark?

Discussion in 'Lighting and Electrical' started by arguevera, Aug 16, 2017.

Tags:
  1. arguevera

    arguevera New Member

    Joined:
    Jul 16, 2017
    Messages:
    11
    Likes Received:
    2
    This is more of an engineering question, but I am curious, given that the CDI only takes in two wires (for what I assume is positive and neutral), how does it know when the piston is located to fire a spark?
     
  2. wheelbender6

    wheelbender6 Active Member

    Joined:
    Sep 4, 2008
    Messages:
    3,805
    Likes Received:
    6
    There is a sensor on the crankshaft, if it works like a motorcycle CDI.
     
  3. 2door

    2door Moderator
    Staff Member

    Joined:
    Sep 15, 2008
    Messages:
    16,301
    Likes Received:
    24
    Wheelbender is correct. There is a magnetic signal provided to the CDI generated from a rotor, or rotating magnet on the crankshaft. The magnet, or rotor is indexed to the crankshaft which determines piston position.

    Tom
     
  4. Russell

    Russell Active Member

    Joined:
    Apr 19, 2009
    Messages:
    1,173
    Likes Received:
    4
    I would like a more detailed answer! A waveform would B good.
     
  5. xseler

    xseler Well-Known Member

    Joined:
    Apr 14, 2013
    Messages:
    2,700
    Likes Received:
    39
    Magic!!
     
  6. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,369
    Likes Received:
    35
    you might want to read the 'roll your own CDI' threads
     

Share This Page