While the SAG thing might get you heart rate up there with a cross country
runner, it is not fatal. It is a warning that plug fouling is ocurring, and
action of some sort is required. Usually lead salts from aviation low lead
fuel building up on the porcelain. This is the same as a low value resistor
shunting the plug gap. So energy in the gap is reduced in increasing amounts
until there is not adequate energy left to jump the gap. Starting with a
small gap takes away the warning that SAG really is. The plug might be
dreadfully fouled by the time it starts to miss fire, and then there is no
quick fix to get home on. (if you forgot the box of new plugs and a plug
wrench).  With a CD or MSD system the plug will fire with a giant blob of
crap building up on it. On the one hand you could say this is a great thing.
But eventually you need to check the plugs as part of some maintanance
program. Should the plug load up completely, the CD or MSD is not going to
help you, and that plug is finished. So now the fact that it ran great and
sounded good right up to the instant it quit running is not a help.

I would run an MSD on the leading plugs in any case. Let the trailing
plugs show you the SAG when it develops. If you are not screaming the
engine, there is no need for the super small plug gaps. Then with the gaps
reccomended by Mazda, SAG give you an easy fix for more hours of power if
you just tighten the gaps to go home. Or better yet put in the new plugs.

Tracy's system might need a load of some sort or a signal transformer to
prevent damage while triggering another system instead of charging a coil
primary.



Lynn E. Hanover