Pertronix Ignitor question, and any real benefit to "performance" spark plug wires?

[D.Hearne]

Ok, you lost me, was I right ?

 

[splinterddt]

So you think the current increases as the voltage increases? Power is voltage x amperage. The primary has 12 volts and the current (lets take a flame thrower as an example) is 12/1.5 or 9 amps. The coil is drawing 12 x 9 = 108 watts. The secondary has about 40,000 volts. If what your saying is true, current goes up. Lets say it stays the same. So how much power is on the secondary...40000 x 9 = a crap load...impossible!!!! The power on the secondary is actually lower than the primary since there is loss with everything...nothing except super conductors is lossless. So what is the current at the secondary...lower than 108 / 40000 or 2.7 milliamps. Current does not do it here...voltage does. Voltage is like pressure in a hose, curent is like the amount of flow in terms of gallons per minute and resistance is like pinching the hose or the friction of the walls of the hose on the water.

Voltage is amps x resistance, but your looking at it wrong. The voltage across the plug wire is small. The voltage across the spark plug gap is very large. The voltage across the plug wire is a couple of volts at most. Thats why when marketer's try to sell you plug wires with "low resistance", it makes no difference in the power transfer because the resistance of the spark plug gap is much much higher....hundreds or thousands of millions of ohms vs. a few hundred ohms. The very high voltage can turn a normally very good insulator into a conductor (air in this case).

I do this crud for a living...Masters degree Electrical Engineering.

Okay, I see the problem. After dicussing this with my co-workers (Ford dealership mechanics), we seem to think you are trying to apply AC voltage therories to a DC application. Watts is not a important factor in automotive electrical systems. Back to the example; 1.5 ohms at 12 volts is 8 amps. When you apply 40,000 volts to the same 1.5 ohms you get 26,666.66 amps. The only constant is the resistance (ohms). As voltage increases, the amps increase. If you look at high voltage power lines, you could physically touch a line carrying 100,000 volts. As long as you do not create a path to ground thus completing the circuit and causing current flow. Air has a extremely high resistance and to overcome this resistance the coil greatly increases the voltage to allow current flow (amps) across the air gap.

I also do this crud for a living...ASE and Ford Certified Auto Technician.

Oh yeah, Pakrat, electricity and water are alike in how they ACT. The comparison is made to understand the how things work and their therories. If it is easier, electicity ACTS like a fluid.

 

[stang-69]

Okay, I see the problem. After dicussing this with my co-workers (Ford dealership mechanics), we seem to think you are trying to apply AC voltage therories to a DC application. Watts is not a important factor in automotive electrical systems. Back to the example; 1.5 ohms at 12 volts is 8 amps. When you apply 40,000 volts to the same 1.5 ohms you get 26,666.66 amps. The only constant is the resistance (ohms). As voltage increases, the amps increase. If you look at high voltage power lines, you could physically touch a line carrying 100,000 volts. As long as you do not create a path to ground thus completing the circuit and causing current flow. Air has a extremely high resistance and to overcome this resistance the coil greatly increases the voltage to allow current flow (amps) across the air gap.

I also do this crud for a living...ASE and Ford Certified Auto Technician.

Oh yeah, Pakrat, electricity and water are alike in how they ACT. The comparison is made to understand the how things work and their therories. If it is easier, electicity ACTS like a fluid.

How do you tranform DC ?? As far as I know transformation is only possible with AC, or ...


By the way 26 000 + Amps, are you aware how much that is ...
And no, as voltage increases, amperage decreases and the other way around (how would it be possible to weld with 130A on 20 A breaker ??) . The power is constant P= V x A, you can not expect to have more power than you started with.

 

[Pakrat]

Oh yeah, Pakrat, electricity and water are alike in how they ACT. The comparison is made to understand the how things work and their therories. If it is easier, electicity ACTS like a fluid.

It's probably also note worthy at this juncture to point out that in either theory or reality, I really don't give a poop about the subject. However, having had the priviledge of seeing both of them act, I disagree. While waters talents are more cohesive, electricity delivers a far more shocking and memmorable performance.

 

[D.Hearne]

How do you tranform DC ?? As far as I know transformation is only possible with AC, or ...


By the way 26 000 + Amps, are you aware how much that is ...
And no, as voltage increases, amperage decreases and the other way around (how would it be possible to weld with 130A on 20 A breaker ??) . The power is constant P= V x A, you can not expect to have more power than you started with.

A/C and D/C are transformed from one to another all the time. Very common in Diesel locomotives.

 

[splinterddt]

After dicussing this topic with my co-workers, again. They believe that there is truth in both ideas. I have searched all the manuals I could find, and a little on the internet. All info about ignition coils say that the coil "transformes" battery voltage to "induced voltage" to carry enought CURRENT to arc across the spark plug gap. The wider the gap, the more current is required to jump the gap. Everyone suggests to keep plug wires separated to prevent cross-firing due to induction, which is caused by high CURRENT flow. Through all the info I came across, I could not find any current output specs. Automotive electrical systems depend on sorce voltage(battery) and amp readings. Power (watts=VxA) is unimportant. Battery voltage stays constant. Amps fluctuate in relation to the resistance the battery voltage goes through.

Elecrticity does transform. There are a variety of sensors and modules that transform DC voltage to AC, and vise-versa.