Replacing points with an electronic module (Pertronix, Breakerless SE, etc.) does nothing to increase the output of the secondary side of the ignition system; all it does is replace an electro-mechanical switch (the points) with an electronic switch. The coil (and its rise-time characteristics) determines secondary output, not the switch. If you keep the stock coil, all the electronic conversion does is eliminate the need to set dwell once a year.
That's why modern engines (like the Chevy LS series, etc.) have individual coils for each cylinder - each coil primary winding has eight times longer to saturate before discharging than a single coil does for the same application.
Well John, with all due respect to you and others on this board, you are wrong about this one and how a step up transformer works. Let me explain: Step up transformers, aka ignition coils, have several factors that determine their output. The number one factor in this equation is in fact switching time. This one factor is fundamental to the understanding of Inductors. Coils are nothing more than two inductors that are electrically adjacent to one another. The other factors that are involved are the turns ratio, saturation time and of course the primary and secondary resistance of the coil windings.
A coil works on two principals: Self inductance and Mutual inductance. Self inductance is present anytime a wire (conductor) is coiled and a current is passed through it and then abruptly changed. That means that the current flowing through a coil of wire at a steady state will not create a spike in voltage on that same coil of wire. Any time a current is passed through a conductor a magnetic field will be induced. If the current remains steady so does the magnetic field. Interrupt this current flow and the magnetic field collapses around this coil of wire thus inducing a high voltage "spike" in this same coil of wire. The key here is a "Change in" or "Delta" current. If the current flow is increased or decreased that equals a change and therefore you will get a voltage increase relative to that change in current. The NUMBER ONE FACTOR in creating a higher voltage spike in a coiled wire is simply how fast you can create a change in this current. Points do not do well here. They do NOT interrupt coil primary current very fast. In fact if you observe this on an oscilloscope you will NOT see a square wave representing current but you will see a sloping (time vs current) of decreasing current. The enemy of self induction. When the points are closed the current is flowing at a steady state in the primary side of the coil. As they begin to open using a mechanical cam they do NOT open instantly. They open (relatively) slow and this allows current to keep flowing across this small gap until they are finally open far enough to stop the current flow. That is also why points become pitted. This is a result of material being transferred from one contact point to the other when current flows across the points. The number one improvement that was made to ignition systems was to replace the points with a transistor. A transistor works at the speed of light (186,000 miles per second) So, instead of being forced to open/close by the limits of the distributor cam profile, or engine rpm, the transistor can stay closed far longer than points can and increase saturation time AND switch this coil primary current far faster and exceedingly more abruptly. Electronic ignition modules have an increasing dwell period with rpm. Points do not. On an oscilloscope the primary current with transistors looks like a square wave rather than a ski slope. Why do you think transistorized ignition was offered on cars in the 1960s? It was a HIGH PERFORMANCE option because in fact, it was better than a points ignition could ever be. The primary coil current was controlled by a transistor, not a set of points.
Mutual inductance is a property that allows the transfer of energy from one coil to another coil nearby. So if you take this primary coil and you put it around the secondary coil (the one your coil wire is attached to) and then collapse this magnetic field that surrounds the primary coil, all of this energy is absorbed by the secondary coil. Because the secondary coil has far more coils in it than the primary coil does, the voltage is increased relative to the number of coils that it is increased over the primary coil. It's that simple.
Turns ratio: This is another factor in determining coil output. Turns ratio is simply a mathematical number for the number of coils (turns) in the primary side vs the number of turns in the secondary side of the coil. A turns ratio of 100-1 means that if there were a 100 primary coils windings on the primary side then the secondary side has 10,000 coils windings. This is very important because it has a lot to do with the peak voltage that can be obtained on the secondary side. Increase the turns ratio and you will increase the secondary output voltage but this comes at the expense of the current on the secondary side. If you increase the voltage in the secondary side you will decrease the current by a relative amount.
The output of any ignition system is determined in the engineering of the system and with points ignitions the engineers were hog tied. The power (watts) of the system is determined by the voltage and current on the primary side. The current is determined by the resistance of the circuit and the voltage on an automobile is a nominal 14 volts when running. That's also why the resistance of the coil is so important with points ignitions. You can not lower it too much or you will increase the coil primary current to a point where the points will fail or constantly just arc and not create any high voltage. Typically in a points ignition system primary current is 4 amps and about 14 volts. That equates to 56 watts (V x A = watts). At the spark plug when you are seeing 20,000 volts remember you still have a 56 watt system. You can't make energy for free. So if you have 20,000 volts with a 56 watt system you now have .0028 amps at the spark plug. Increase the spark plug gap and you will increase the voltage but you will decrease the current and decrease the duration of the spark. It's really an energy equation (joules). Spark plug gap is important. Ever notice how small it is with points ignitions? It's doubled or more with electronic ignitions. And yes, there is a reason for that. Leaner A/F ratios in the 1970s required it. Electronic ignitions have 10 amps of primary current and 14 volts. That's 140 watts of ignition power. 2.5 more than the points ignitions without doing anything more than replacing the points with a transistor. The points can not handle the 10 amps. They are only good for about a maximum of 4 amps. A transistor can easily handle 10 Amps. What this means is that the output voltage at the spark plug is 2.5 times higher. That's something to brag about.
Saturation time is nothing more than the amount of time the current is flowing through the primary side of the ignition coil. Now here is where most people just don't understand electricity and more to the point ignition coils. Even with points the coil saturation time is rarely a factor. Electricity (electrons) move very quickly and thinking that time (in human terms) inhibits this is crazy. As I said earlier, coils are inductors. Inductors are really just coils of wire usually with a metal bar through or around them to add permeability. When current flows through conductors (coiled wire) a magnetic field exists. A magnetic field is nothing more than air, or conductors, saturated with electrons. As the current begins flowing in a circuit, the magnetic field builds. As this field (electrons) increases so does it's resistance to allow any more current to flow. Why? Because similars repel. Electrons stored in the area around the coiled wire are the same polarity as the electrons trying to flow in to this same wire. They naturally repel one another and THAT is what ultimately determines the saturation time in any particular circuit. Saturation time is non linear and therefore the points only inhibit this property at very high rpm where coil "on time" is physically less than the minimum time for the inductor to saturate to at least 75%. Again, it's primary current switching time (quickness) that determines the output. Inductors resist a change in current and Capacitors resist a change in voltage. That's why you have capacitors on your car for radio suppression and not inductors.
What does all this have to do with points? Points do just the opposite of what you need when you need it most. Let's examine an engine at idle. Obviously the demand is low so there is rarely a problem then. At idle the points have a relatively decent amount of TIME, NOT DWELL, to get the job done (let the coil become saturated with electrons). Dwell on points ignitions is FIXED and does NOT change with rpm. What is the difference between dwell and time? Time is, well, time. It is constant and marches on at a steady rate. You can get work done in a fixed period of time. Dwell means "time spent" or "duty cycle" relative to another dependent variable. Ignition dwell is expressed in the amount of degrees the crankshaft rotates. So, if the dwell of your points is 30 degrees that means the time the points are closed "duty cycle" is for 30 degrees of crankshaft rotation. Not very long. How long does it take for the crankshaft to rotate 30 degrees? Well, at idle, 600 rpm, the crankshaft turns 3600 degrees every second. 30 degrees of crankshaft revolution takes exactly .0083 seconds. That's how long the points have to saturate the coil. That's not a lot of time to get the job done and we are stuck with this due to the cam profile of the distributor and the fact that the points have to physically open to a .019 gap then return to the closed position. As you increase rpm you increase demand on the ignition. What happens to the points with this increase in rpm and demand? Let's go to 3,600 rpm a six fold increase in rpm. The dwell has not changed, it can't, the points are mechanically connected to the engine. So at 600 rpm the points have .0083 seconds to saturate the coil now at 3,600 rpm the points still have 30 degrees of dwell but now 30 degrees of dwell only lasts .0013 seconds. So you see as the engine rpm increases along with the demand on the ignition the opposite happens. The TIME that the points have to stay closed is decreased but the dwell stays the same. You need more TIME to saturate the coil and the faster you rev the engine the less time the points have. Simple. Oh yeah, that's why there were dual point ignitions back in the day. They split the chores and basically doubled the time they had to work. Even they were limited by rpm however.
Electronic ignitions use a transistor, NPN type, to switch the coil primary current. This has several advantages number one of which is of course how FAST it can switch from full current flow to zero current flow. And that is what really made the biggest improvement in secondary output. Switching time. Electronic modules also have the benefit of being able to INCREASE the dwell with increasing rpm. They can do this because the module can "read' the rpm from the pole piece and realize the rpm increase thus increasing the "on time" or "dwell" of the switching transistor. Unlike points ignitions, electronic ignitions will not sign off at a particular rpm due to lack of TIME. Transistors switch from on to off at the speed of light. Of course there are no moving parts so there is no maintenance and they last the life of the vehicle so long as an amateur does not get their hands on them.
Distributorless ignitions have been around since day one. The LS series cars are old hat. Coil over spark plugs systems were on motorcycles decades ago. Unfortunately, the Japanese understood this and were willing to use this technology to make better vehicles. They did and here we are today. The reason for coil per cylinder is not why you think it is. It is there so that the ECM can control primary current on a "per cylinder basis" Not because they want to increase saturation time. That problem was solved long ago with electronic ignitions. All modern OBDII cars use a variation of cylinder spark control for emissions, self diagnostics and fuel mileage. Most importantly the ECM can inhibit spark on a number of cylinders or cylinder on extreme decel conditions as well as fuel pulse to completely shut off a cylinder and eliminate that emissions from that cylinder. They also have these because the government mandates the manufacturers meet a federal emissions warranty that in many cases is 100,000 miles. The engine can not exceed emissions more than 1.5 the FTP. The only way to achieve this is eliminate possible failure areas in the secondary ignition system. The area most likely to cause a cylinder misfire. Misfire is bad news with OBDII systems and that's why you do not see coils with spark plug wires. You will also notice they use platinum tipped spark plugs too. All these things you see on a modern car are there for these reasons. It's more complicated than this but I've gone on way to long already.
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