>I'm still not convinced about these, but I'm willing to listen to
>arguments to the contrary.  Basic physics says that the spark will only
>jump to one ground electrode on any particular firing of the plug, so
>what's the benefit?
>

True, for any given pulse, there will only be a single spark from the spark
plug. However, with 4 electrodes, the optimum gap will be achieved over a
much longer period of time, thus giving the plug a much longer life and
better performance and emissions over that life.

Each time there is a spark, the outer electrode erodes a bit. As the one
erodes another will provide a better path for the spark. As it erodes,
another electrode will then have the best path. And on and on.

The problem with more and more electrodes is that the spark becomes more and
more shrouded. That is, the spark is kept concealed from the rest of the
combustion chamber. Drag racers, among others, are known to "index" their
spark plugs so that when installed, the gap in the plug is always located
for best flame propagation within the combustion chamber. If you keep
putting more and more electrodes on that spark plug, it will become
increasingly difficult for the spark to do its job.

I think that there is a benefit to a well-engineered multi-electrode plug.
However, I also believe there there is a definite limit (and personally I
believe that the limit is less than 4) as to how many electrodes is best.

Just my thoughts.

Bruce

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