The Old Standard Ignition System. Battery. Coil. Points. And Condenser....

[SeaMonkey]

There seems to be some confusion regarding the function and
purpose of the Capacitor which parallels the breaker points in
the Kettering Ignition System (aka Delco Ignition System.)

The capacitor was typically 0.22 MicroFarads up to 1.0 Micro-
Farad.

Here are some links which offer some clarity, but not a full
understanding.  I do believe Miles Higher has the
understanding of fullness.

Wikipedia on Ignition Systems

Kettering Ignition System

Delco Ignition System

Battery Coil Ignition

The Auto Ignition System

Whenever a Coil and a Capacitor are series connected
a resonant circuit is formed.  This is the case in the
Kettering System when the breaker points "open" to
produce the spark at the spark plugs.  But, the question
is, is the "resonance" of the primary circuit responsible
for the "hot spark" or is it just the capacitor itself which
makes the difference?

Calculate the resonant frequency of the primary circuit
to acquire additional comprehension.  The inductance
of the primary winding of the typical ignition coil is said
to be about 8 MilliHenries.

Is the "resonant frequency" of the LC combination high
enough to affect sparking action?

Automotive Ignition Coils

Ignition Coil Circuit Simulation by Bowling and Grippo

Automobile Ignition Question discussion

What is the function of the capacitor?

[MileHigh]

Here is a nice Aussie YouTube mechanic that has some nice clips but there are a few imperfections here and there.

In the first clip below he gives a nice overview (I found the mother load through him) and he made a mistake that I corrected for him with a comment on the clip.  I hope he takes the comment nicely.

The clip:  https://www.youtube.com/watch?v=xNllhOWGHhg

My comment on the clip:

<<< Hi, you have very nice informative clips.  I am not a car guy but I have a background in electrical engineering and I just want to clarify a point for you.  At 9:35 in discussing the oscillations between the condenser and the primary you say "to get the most amount of energy (into the spark) we have to increase the speed of the flux lines crossing over."  This is not what is happening.  What you are saying is a popular misconception.  Here is the proper explanation:  When the HV secondary ignites the plasma there is a continuous plasma burn with the secondary at a constant voltage at say 800 volts.  During this time the secondary is on a continuous burn pumping the stored magnetic energy into the plasma spark.  This is an "automatic" process that has to do with the way inductors work.  It's sort of like a charging bull with a momentum of its own.  You mentioned that coils have electrical inertia to energize them.  This is the inertia working in the opposite direction while the coil de-energizes.  So the secondary discharging does not "need" the primary to oscillate with the capacitor to "get the most amount of energy (into the spark)."  In technical terms the discharging secondary inductor is a "current source" (as opposed to a voltage source.)  The primary oscillating with the capacitor is a secondary process that will make the main discharge of the secondary into the plasma "wiggle" a bit because of the mutual inductance a.k.a. transformer coupling.   >>>

Here are a few other clips from the mechanic that may be of interest, but there may be some imperfections in them:

https://www.youtube.com/watch?v=fja2XH8AyyE

https://www.youtube.com/watch?v=V8M-07nluAE
 

[MileHigh]

The Aussie mechanic on YouTube liked my comment.

I have one more comment to add that in a way is going full-circle.  When the current in the resonant LC is going counter-clockwise during the resonant ring-down, then the battery becomes a power source that adds a (presumably) small amount of energy to the plasma burn.  This is the infamous step-up transformer action and would only apply while the plasma is lit.

[citfta]

I have only a couple of things to add.  First off leave ME out of your pms!  I have been gone for a week and when I got back my email box was filled with emails telling me I had a PM.  Then I log in and had to delete tons of PMs that I did not take time to read.

I have skimmed this thread enough to understand the MH has finally admitted that he was mostly wrong about how the system works.  He still insists, if I understand his posts that there is no resonance in the ignition circuit.  Then WHAT IN THE WORLD ESTABLISHES THE RING DOWN FREQUENCY?  Come on MH.  We are not all morons here that you can baffle with that kind of BS.  I have already explained how the system works.  I will not waste any more time on this.  I just don't care that much anymore that there are people who don't want to learn the truth.

Carroll

[profitis]

" I have been gone for a week
and when I got back my email box was filled with
emails telling me I had a PM.  Then I log in and had
to delete tons of PMs that I did not"

That's terrorville.I'm so happy I don't have such things
to worry avout anymo