ok this is going to be a doozie so bare with me!
timing, ignition events and all things ignition
This sounds easy on the surface but this is actually one of the most complicated subjects in the automotive world
First we need to get definitions of the different parts.
By the time you are done reading this, you will know exactly what timing is, dwell/ charge time/rise time, overcharging and problaby more than you could ever imagine and probably have a headache to boot
What is a winding/turn, primary winding and secondary winding in the ignition coil?
Winding/turn is the number of “loops” around the ferrite or air core inside the “ignition coil”. Like wrapping a string on a yo-yo, each time the string overlaps itself is considers one winding/turn. The primary winding is what influences the resistance of the coil to the igniter. The less windings/turns, the lower the resistance. This becomes crucial in trying to match a coil to particular application. Why? Get an ignition coils with a very low primary resistance and all you will have is a smoke show from most stock igniters as they try to put their output through almost a dead short (resistance wise).
But Figgie that doesn’t explain how I can get 20,000 volts out of the coils.
(Oversimplification ahead!!)
So we know that the primary coil is what is present to the igniter. That leaves the secondary winding the secondary winding is the same in essence as the primary winding except this is what connects to the spark plug. The difference though is in what happens between the two windings. For voltage to increase the secondary winding must have a higher amount of turns vs. the primary winding. This is what is known as turn ratio. So if hypothetically speaking you have one turn on the primary side and two turns on the secondary side then you have a turn ratio of two to one (2:1). So in this hypothetical coil if we were to apply 5 volts to the primary winding, we will see 10 volts at the secondary winding at a lower ampere. I will not get into the physics of it but ohms law and energy conservation theory play into it. I will let someone else explain that  So let go further
Say an MSD Blaster coil
http://www.msdignition.com/coil_blaster_1_8200_8202_8223.htm
It shows a Primary resistance of .7 ohm
.
Turn ratio is what we are interested for the sake of this discussion. 100:1. Well, well, well, now we are starting to get a clearer picture. So with a 100:1 turn ratio, if we input 5v then we will have 500 volts on the secondary side. Hmm we are missing a bit of zeros aren’t we? Well at this stage you are right
so how do we achieve 20,000+ volts?
Well now comes the fun part
The Ignition coils are nothing more than inductors (electronic world), choke coils radio transmission world), low pass filter (car audio world/speaker building world). Well inductors are like capacitors in which they can store energy. The rate at which they store this energy in the primary coil is the charge time/rise rate or as we know it in the automotive world, dwell time, which I will use here on out. Just like a capacitor it has a limit as to how much energy it can store. Go above the dwell time and it gains nothing but an over heated ignition coil. To little dwell time and you will not have enough energy (read misfire is highly likely).
What the hell does this have to do with ignition Figgie??
Well we haven’t put all the pieces together yet so patience 
Well once the ignitio coil reaches saturation the amperage soars (usually around 6.5amps to 10 amps @ 12 vdc on most typical ignition systems). Ok, so what you say? Well quit interrupting and pay attention you impatient students! Well now that we have all that energy flowing through the primary winding, let cut the power to it. Say what figgie? Yes cut the power to the primary winding. Now here is where the actually bump to 20,000+ volts begins  Since the coil has all this energy flowing through it. The stop of the energy actually causes the magnetic field that is produced by the primary winding to collapse. This collapse causes those 12v to jump to nearly 250v at that instance in time time. When those 250v go into the 100:1 turn ratio of the ignition coil. We have 25,000 volts popping out of the secondary winding, ready to jump the gap at the spark plug or kill you if you touch the secondary winding side 
This is of course an extremely simplified overview but you get the gist 
What is timing?
Timing is the term given for when the process to start the combustion happens in an internal combustion engine. Timing is based on a bunch of factors to include flame propagation, combustion chamber design etc. The ideal timing is not at 0 TDC as at that point the piston has ZERO leverage on the crank. The ideal time is somewhere around 12 degree after top dead center. So why do we start the timing event at 10 degree before top dead center? The answer is actually simple. The combustion process is not instantaneous. It actually takes time to initiate the flame front and go through the combustion chamber to ignite the entire mixture. By the time the highest cylinder pressure is achieved by the combustion process, it will be around 12 degree after top dead center  As RPM increases then we have to start the ignition process earlier in the stage. If we add more oxygen to the mix (higher boost) then we actually have to take away timing as the oxygen quickens the flame front. Advancing the timing might net you some power or it might not. If you advance the timing to much then you end up producing the peak cylinder pressure before the maximum leverage is applied to the crank. What this usually means if there is enough energy to move a 3400 lbs car. You best believe there is enough energy to chew threw rod bearings melt pistons or bend rods in a heart beat if the timing is to advance. If the timing is too retarded then you will be past the maximum leverage point for the crank (around 12 degree after top dead center) and then past the peak cylinder pressure, or in short lost power.
What I explained here is over simplified. There is a lot of science and physics involved with this that I did not mention but I tried to make it easy to understand
-Figgie
:naughty:
