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Connecting oscilloscope to car ignitions

Discussion in 'Electronic Basics' started by RKovach, Nov 27, 2003.

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  1. RKovach

    RKovach Guest

    I have read that you can use a lab scope to check the secondary firing
    patterns by connecting an inductive lead to the coil wire on #2 channel, and
    connecting another lead to the #1 spark plug wire on #1 channel, and use it
    to trigger the signal. This will show all the plugs, in the firing order, in
    1 trace.
    Can this somehow be used on a distributorless ignition system that does not
    use 1 coil for all the plugs? Is it possible to use 5 pickups, for a 6 cyl.
    engine, all wired together, and connect this to the #2 channel and connect
    the #1 as above to get the same results?
     
  2. Bob Grimm

    Bob Grimm Guest

    I assume you are referring to DIS (Direct Ignition) as oposed to COP
    (Coil-on-plug) (another form of DIS) Ignition.

    Unfortunately no you cannot just hook up 6 (for a six cyl) inductors
    and view a readable pattern. Most DIS ignition systems fire the
    coils in pairs with the secondary voltage travelling thru the current
    cylinder to be fired and "returning" thru it's companion cylinders
    plug/wire and back to the coil completing the circuit.

    Unless it is an Automotive Scope that can be configured to handle/
    filter that reverse polarity waste-spark you will not get an accurate
    display of the firing lines.

    This is also why a conventional rpm inductive pickup reads 2x
    the acutal rpm when clipped to a DIS wire, since it reads that extra
    waste-spark firing (during the cylinders exhaust stroke).

    -BG
     
  3. I'm trying the same thing. My problem how do we capture infrequent events if
    we're using normal scopes. If you succeed, please let me know. How does a
    capacitive pickup work or an inductive lead? Anyone know?

    Here take a look: This is a capacitive pickup which connects around the
    insulation of an ignition circuit component such as a plug wire for scopes.

    Secondary Ignition Pickup http://tinyurl.com/xoox

    Indi
     
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