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Re: Dual-Plugging Question...

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  • lgattmaniii
    Hi all, Just my 2 cents,but I have to agree with Swiss as in using a Snap-On MT1665 Digital oscilloscope to veiw and measure secondary wave forms and KV
    Message 1 of 12 , Dec 1, 2002
      Hi all, Just my 2 cents,but I have to agree with Swiss as in using a
      Snap-On MT1665 Digital oscilloscope to veiw and measure secondary wave
      forms and KV readings shows his ststement to be true(it may
      never...).The KV reading per spark lead(sparkplug) should not exceed
      40% of the rated coil voltage at any time,to insure proper spark under
      all conditions.On Wasted spark normal systems(2 cylinders-1 dual plug
      coil),the true firing KV is usually in the 6 to 14KV range and the
      wasted firing is in the 0 to 4KV range.So,if you use a dual plug coil
      on a single cylinder,the output of the coil will be between 6 to 14KV
      on each sparkplug or a dual plug coil that needs to put out a total of
      12 to 28KV.On a coil that can put out 40,000 volts,this leaves
      anywhere from 28 to as low as 12KV in reserve.Voltage requirements
      depend on a number of conditions and are as follows:Things that
      require a High output:Eroded sparkplug electrodes;high secondary
      circuit resistance;open secondary circuit;high primary
      current;sparkplug gap wide;temperature of the electrodes being cooler
      than normal;dull shape of the electrodes;polarity of the center
      electrode being negative;retarded ignition timing;fuel mixture being
      very lean or very rich;high compression;and cooler combustion chamber
      temperature.Lower Voltage as follows:grounded secondary
      circuit;primary circuit fault(resistance);narrow sparkplug gap;hotter
      temperature of the electrodes;sharpe shape of the electrodes;polarity
      of the center electrode being positive;advanced ignition timing;rich
      fuel mixture;low compression;and hotter than normal combustion chamber
      temperature.I hope this can help. Louis....

      --- In mc-engine@y..., "Jim Schneider" <swissscf@c...> wrote:
      > Understand that the spark jumps whenever it reaches the voltage and
      current
      > level that is required for the plug gap and the combustion chamber
      > conditions. With a 30,000 or 40,000 volt coil, it may NEVER have to
      put out
      > these kinds of volts to get the spark started. IF a dual output
      coil has
      > enough voltage available to spark a pair of parallel plugs, it will
      be fine.
      > It IS better to have excess power available.
      >
      > Swiss
      >
      > ----- Original Message -----
      > From: "Mike Wright" <mwright@g...>
      > Subject: Re: Dual-Plugging Question...
      >
      >
      > > 1. Using a twin output coil, is NOT recommended... I know others
      > will nix
      > > this.. but do the electronic math.. if you run a 40,000 volt twin
      > coil, you
      > > get 1/2 voltage to each plug (under compression).
      >
      > Ron (and others)
      >
      > Forgive what may be an amateur question, but electrical stuff has
      > never made me very comfortable. What's the math for a Guzzi vtwin
      > running dual plugged heads and 2 sets of points.
      > Conventional "wisdom" in the Guzzi community says to run 2 twin
      > output 3 ohm (I think) coils. If I wanted to run 4 individual coils,
      > what's the best way to do that?
      >
      > Mike Wright
    • davisonx
      Long ago in the dark ages before I had the Speedvision channel with coverage of World Rally (my wife would argue that the dark ages began AFTER I got
      Message 2 of 12 , Dec 13, 2002
        Long ago in the dark ages before I had the Speedvision
        channel with coverage of World Rally (my wife would
        argue that the dark ages began AFTER I got
        Speedvision), a high-school friend of mine had a well
        used 4 door Subaru. Front wheel drive, naturally
        aspirated, far from "sporty". However, because it had
        a manual transmission, a somewhat interesting exhaust
        note, and an owner who couldn't care less for the
        condition of the car, it was used for all sorts of
        on-road, off-road, and airborne adventures.

        I will forever appreciate the fact that the Sube would
        seem to take on any challenge and keep on chugging.
        The job of the back seat passengers was to kick the
        floor pans back down as they got hammered inward. The
        car was finally done in by a taking a large puddle,or
        small lake depending on your perspective, at high
        speed and sucking water into the engine, knocking a
        cylinder or two out of whack. We never did tear down
        the engine to see the damage, and I regret it now. It
        was limped into our school auto shop and donated as a
        project car. I recommended sending it back to Subaru
        with a list of accomplishments. It would have made a
        great museum piece. Now, any time I watch World
        Rally, I feel like "been there done that"

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