ignition coil questions
I don't have the math skills to do an in-depth analysis of all that is involved with ignition, and of course there are at least 4 different major systems
Magnetos, which generate their own primary power
The old (Kettering) points systems, which work the same as the Mopar ECU/ breakerless system, IE an electronic switch
The HEI style systems which operate somewhat differently
The various capacitive or inductive discharge systems, which work more like an electronic strobe/ flash on a camera --they charge up a large capacitor and then discharge that energy into the coil
But the OTHER aspect of high performance coils that I'm aware of involves the secondary SYSTEM, IE, coil wire, cap/ rotor, plugs, wires. Coils do not produce voltage "in the way" that say, your 12V battery or 120V wall outlet does, IE a fairly stable voltage over a fairly wide range of current.
Ignition coils are "load sensitive," meaning that the LOAD which the rest of the secondary system presents to the coil affects it's power and voltage output. You can SEE this in a scope pattern. What is called the "firing line" is the point and the time in which the plug fires, and it "drags down" the secondary voltage, depending on plug gap, cylinder conditions including pressure and A/F mixture, etc. A fouled plug will pull the voltage down even more
In the pattern below, the first high spike is a very short moment in time when the points open or the ECU triggers, and the spark starts to form. If there was no plug / wire connected, this spike would be HUGE, much bigger. The little "squiggle" immediately to the right is the plug firing, the "firing line." This shows grapically how the spark voltage is "loaded down" by the plug and wire impedance. When the plug stops fireing, which is due to the coil voltage finally "running out", you see the little "ramp" sliding down as the relatively small amount of coil energy falls off, and the step at the right of that is the points closing, or in the case of a Mopar ECU, the ECU turns the coil back on to recharge. This "recharge" known as "dwell time" is the time that the points are CLOSED or that the ECU is turned on. The next spike happens all over again as the points OPEN, or the ECU triggers and turns the coil OFF
Years ago, Champion spark plugs came out with a plug (forget what the hype was) which had a GAP inside the insulator, which was supposed to allow a better spark to build. A Champion rep explained to me that "these actually worked, UNTIL....." Many of you who are old enough remember that the old GM distributors used to have a LONG and a SHORT rotor. It turns out that the short rotor NEGATED the advantages of the Champion plug. Additionally, for years you could buy "spark boosters" that went either on your plugs or one in the distributor cap coil wire. These were the very same thing --a "spark gap in a can." They were supposed to "intensify" the spark, and were advertised to help old engines which burn oil.
I realize this is not an ANSWER, but I was trying to show that even the old breaker points ignition is more complicated than it appears.
I don't have the math skills to do an in-depth analysis of all that is involved with ignition, and of course there are at least 4 different major systems
Magnetos, which generate their own primary power
The old (Kettering) points systems, which work the same as the Mopar ECU/ breakerless system, IE an electronic switch
The HEI style systems which operate somewhat differently
The various capacitive or inductive discharge systems, which work more like an electronic strobe/ flash on a camera --they charge up a large capacitor and then discharge that energy into the coil
But the OTHER aspect of high performance coils that I'm aware of involves the secondary SYSTEM, IE, coil wire, cap/ rotor, plugs, wires. Coils do not produce voltage "in the way" that say, your 12V battery or 120V wall outlet does, IE a fairly stable voltage over a fairly wide range of current.
Ignition coils are "load sensitive," meaning that the LOAD which the rest of the secondary system presents to the coil affects it's power and voltage output. You can SEE this in a scope pattern. What is called the "firing line" is the point and the time in which the plug fires, and it "drags down" the secondary voltage, depending on plug gap, cylinder conditions including pressure and A/F mixture, etc. A fouled plug will pull the voltage down even more
In the pattern below, the first high spike is a very short moment in time when the points open or the ECU triggers, and the spark starts to form. If there was no plug / wire connected, this spike would be HUGE, much bigger. The little "squiggle" immediately to the right is the plug firing, the "firing line." This shows grapically how the spark voltage is "loaded down" by the plug and wire impedance. When the plug stops fireing, which is due to the coil voltage finally "running out", you see the little "ramp" sliding down as the relatively small amount of coil energy falls off, and the step at the right of that is the points closing, or in the case of a Mopar ECU, the ECU turns the coil back on to recharge. This "recharge" known as "dwell time" is the time that the points are CLOSED or that the ECU is turned on. The next spike happens all over again as the points OPEN, or the ECU triggers and turns the coil OFF
Years ago, Champion spark plugs came out with a plug (forget what the hype was) which had a GAP inside the insulator, which was supposed to allow a better spark to build. A Champion rep explained to me that "these actually worked, UNTIL....." Many of you who are old enough remember that the old GM distributors used to have a LONG and a SHORT rotor. It turns out that the short rotor NEGATED the advantages of the Champion plug. Additionally, for years you could buy "spark boosters" that went either on your plugs or one in the distributor cap coil wire. These were the very same thing --a "spark gap in a can." They were supposed to "intensify" the spark, and were advertised to help old engines which burn oil.
I realize this is not an ANSWER, but I was trying to show that even the old breaker points ignition is more complicated than it appears.
