Multispark

[Edward Hernandez R]

This is a reply to Clint Corbin. I'll try to include as little as
possible form his post, so I apologize up front for the generous
snipping and clipping.

"What is the saturation time of the coil?  If you are charging at a
fast rate, I still see no advantage with one coil/cylinder over one
coil/two cylinders."

I do not know the saturation times of "the" coil. Besides, coils are
designed to suit different applications(single coils vs eight vs
waste spark). If the saturation times are low enough then, true,
that's one less reason for going coil per plug. However, the load on
a coil per plug is much less than the load on a coil per two plugs
(assuming by this you meant waste spark). In addition, half the spark
plugs on wastespark systems erode the ground electrode faster than the
center electrode, so if you want 100,000 mile tune up intervals, you
need double platinum plugs OR customers/dealers/mechanics who are
willing to take the care to install the two kinds of single platinum
plugs in the correct cylinders. Guess how often we count on them to
do it right! Thus, we have to install the fancy plugs in each cylinder
to idiot proof the tuneup.

"Even with one coil/two cylinders you stil have four times (on a 8
cylinder) the number of coils than the MSD has.  Just how high do you
need to take the motor anyway?"

How does 7 grand stike you? You have to remember that you can't apply
an analogy like that to an OEM. I've heard(i.e., this is not fact)
that MSD's do not last long. There is a saying in circle track racing
about how many MSD units you need: one in the car, one in the pits,
and one on the way back to MSD for replacement/repair. OEM stuff has
to last much longer than this(and you know it often doesn't!). Again,
with waste spark, you have to jump two gaps, meaning during your
saturation time, you need to store more energy.

"Once more, with the wasted spark system, you could do all of this
(combustion sensing) with out a problem."

I would debate that since you are trying to sense across two gaps, one
of which is exposed to expanded burnt charge and the other to expanding
and burning change. Surely ion sensing is easier and more robust across
a single gap compared to two in series.

"Any again, why does one coil/cylinder do this(independant cylinder knock
control) any better than the wasted spark system?"

You have me there. That's just a strategy change, so the software guys
would complain which is easier/more convenient but they'd live.

Ed Hernandez
Ford Motor Company
ehernan3 at ed8719.pto.ford.com