Spark Plugs....

[nacelp]

I buried myself again, and rather then respond to all the off list comments,
I'll just try to write it down here.

When the signal for coil fire is executed, the primary side of the coil is
cut off, the secondary collapses inducing a new higher voltage in the
primary, and this continues several times till you get enough secondary
volatge to complete a path to ground.  OK, Now in trying to find ground, the
open ends of the secondary wiring ionize little feelers like lightning does.
They "eventually" once the sec/pri inducded voltages "ring" a few times, to
cross the air gap in the cap/rotor (if applicable), and then the plug gap.
The CD systems since they run on about 400v rather then 12 have a head start
on the ringing process, and hence a faster rise time.
  Now, in any given amount of time a coil can produce only so much energy.
Voltage and Amperage are the variables.  As the voltage goes up, the
amperage goes down.  There is alot of theory that holds some other issues,
but as far as in real world applications, I haven't seen any really
meaningful results, not to ralle the EEs here but, I'm talking put a stop
watch on it and see exactly what the truth is.  Yes, I understand some of
the theories about things work, change, but again I'm talking stopwatch time
here, and that's what blows the wind out of alot of theory, or makes the
various "issues" mute.
  Anyway, getting back to the Multi spark concept.  Since they have this
problem with amperage, what they do to continue the spark as a long as a
conventional system, is light it several times.  The multi spark is only an
attempt to cover up for a short coming of the basic design.  No more no
less, from what I've seen.  I have a Tiger CD that is so old I forgot when I
got it, that still operates just fine, with a single spark.

   By the way, I also, installed this single spark CD, and MSD unit on the
same car, that I had tuned using a convential system on, and found no
differences in HP, MPH, or emissions (3 gas analyser).  The CDs yes on cold
mornings gave a quicker start.
  In a fouling type situation, ie cranking, full choke, low cranking speed
the fast rise time is a great assist, and what most people feel is a good
thing, and gives them the impression that the CD is soooo good.
  Also, alot of folks don't have a clue about jetting, and run rich
smoothest idle.  So having a mulitspark is darn near necessary to light the
fuel that's oozing outta the exhuast.
  The multispark stops at 3K and that's when it needed most.  But, they sell
more of them worring about trying to keep customers happy that are clueless
about mixtures, initial timing.

   There is some theory about flame propagation, and what is meaningful is
subject to opinion.  Several folks make a big issue about the time it takes
from initial ignition to "kernel" to full chamber combustion (or reaction).
Often plug gaps are in the order of .035", those that subscribe to the
kernel theory say that isn't till this "fire" reaches a diameter of .1" the
burn rate is very slow, and it's only after reaching this diameter do things
really matter.  Well, I did some back yard testing in opening gaps up using
low gap cap rotors, and various mixtures trying to find a combination that
would allow me to retard the timing a few degrees and make the same HP.  I
couldn't do it.  I couldn't find 2 degrees anywhere.  So while the MEs might
be sold on this concept in real word applications, it's mute in my book.  I
haven't seen anything that changes timing enough to matter gimmick wise.

  Again I'll go back to what I've said before,     If you find HP by
changing plug styles then it's because of an ignition design fault.  By
styles I'm not talking basic designs.  ie projected nose plugs can make for
a cleaner idle in some applications with no lose of HP.  Side Gap plugs can
reduce detonation in some applications.  There are lots of variables, in the
chambers, but one good spark properly timed should do just fine.   Silver
center electrodes say they ionize easiest, so flame starts easiest, OK, then
why is there so much hoppla about how long platmums last?.  They must erode
the least, and then run the "worst", hmmm, more marketing, I guess.  At $15
dollars a plug (what some 100K plugs go for) sure they can guarantee they go
100K, even if they replace them 4x that still alot more then the (4@ 99
cent) jobs would cost.  While they might have better quality control, I
don't see 15x the better product.

   If changing plugs is such a critical matter that it's worth not doing at
any cost, then, well, a new hobby might be a better answer for you.  Cause
your not going to want to make the effort to get all you can, cause that
means reading plugs anyway.

   Oww, wow, maybe a capacitor in the plug wire, naa, don't wanna go there
either.

Grumpy

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