Coil issue? Runs for 90 minutes and quits

[ndutton]

Here we go again

Hanley and I have very different views on the subject and frankly I'm weary of the exercise. Regarding coils and electronic ignition, the following are FACTS and not subject to interpretation:

1. Once a coil has suffered an overheat episode to the point of shutdown it is permanently damaged internally. After cool down it may return to function but will be less tolerant of even normal heat in the future risking (almost certainly) repeated failures. The problem with a coil overheat is damage to the insulation on the internal windings. Once done, it's done even if it gives the illusion of operation temporarily.
2. Pertronix, the manufacturer of our electronic ignition systems, specifies right in their literature a 4 amp maximum system amperage.
3. Alternators produce more than 12 volts for battery charging and therefore to our entire electrical system when under power. It's inescapable. 13.8 ~ 14.2 volts is the normal range.

Here's where Hanley and I part ways. He is focused on coil input voltage without regard to ignition system amperage. Consider 9 volts coil input (well within Hanley's voltage) and a readily available Flamethrower 1.5 ohm coil. Any thought on how that combination will work? Your voltage as recommended is good without consideration of the amperage and you're screwed.

Same example, different numbers. Coil input 14.2 volts and a Moyer 4.3 ohm coil. Whaddya think now? Huge input voltage per Hanley's rule yet the system amperage is 3.3 amps WITHOUT any supplemental resistance. Notice too that without supplemental resistance you'll have two less wire connections aka potential failure points in the primary ignition wiring.

My point is - now and for the past several years - amperage - amperage - AMPERAGE!

Within reason, the coil input voltage does not matter as long as the system has sufficient resistance via coil, supplemental resistor or a combination of both to render the system amperage below 4 amps (per Pertronix). Good engineering practice is to build in a margin of safety below the maximum.

[hanleyclifford]

Hanley and I have very different views on the subject and frankly I'm weary of the exercise. Regarding coils and electronic ignition, the following are FACTS and not subject to interpretation:

1. Once a coil has suffered an overheat episode to the point of shutdown it is permanently damaged internally. After cool down it may return to function but will be less tolerant of even normal heat in the future risking (almost certainly) repeated failures. The problem with a coil overheat is damage to the insulation on the internal windings. Once done, it's done even if it gives the illusion of operation temporarily.
2. Pertronix, the manufacturer of our electronic ignition systems, specifies right in their literature a 4 amp maximum system amperage.
3. Alternators produce more than 12 volts for battery charging and therefore to our entire electrical system when under power. It's inescapable. 13.8 ~ 14.2 volts is the normal range.

Here's where Hanley and I part ways. He is focused on coil input voltage without regard to ignition system amperage. Consider 9 volts coil input (well within Hanley's voltage) and a readily available Flamethrower 1.5 ohm coil. Any thought on how that combination will work? Your voltage as recommended is good without consideration of the amperage and you're screwed.

Same example, different numbers. Coil input 14.2 volts and a Moyer 4.3 ohm coil. Whaddya think now? Huge input voltage per Hanley's rule yet the system amperage is 3.3 amps WITHOUT any supplemental resistance. Notice too that without supplemental resistance you'll have two less wire connections aka potential failure points in the primary ignition wiring.

My point is - now and for the past several years - amperage - amperage - AMPERAGE!

Within reason, the coil input voltage does not matter as long as the system has sufficient resistance via coil, supplemental resistor or a combination of both to render the system amperage below 4 amps (per Pertronix). Good engineering practice is to build in a margin of safety below the maximum.

You're not allowed to get weary, Neil. Actually I have never doubted that your formula has a sound engineering basis. It's just that my approach, while less scientific, also achieves the desired result.

[ndutton]

It's just that my approach, while less scientific, also achieves the desired result.

Not necessarily and that's what I tried, apparently unsuccessfully, to illustrate with my example. I'll repeat the example: 9 volts coil input, 1.5Ω coil. I didn't pull the coil resistance out the air. It's the other one Flamethrower offers and has been tried by at least one forum member attempting to work through coil related shutdowns in the past. It did not go well.

Is there any question the example system is doomed to failure? Even at 9 volts? How about 8 volts? Following your voltage rule, no fair calculating amperage, it's volts only.

We have members coming here for help with what was once a vexing problem (successfully resolved a few years ago) and sending them down a 'voltage only' path that might work depending on whatever coil they might have picked up at the local auto parts boutique (there are 3/4Ω coils too) just adds confusion. There's more to it than just voltage.

Don't get me wrong, voltage is a factor but not the only factor. We have to give these members the whole picture if they are to become self sufficient and expert troubleshooters. Isn't that really the goal?

Kelly's 'Coil Input Information" thread should be required reading as a condition of forum membership. I can't believe after solving the problem nearly 3 years ago we are still going through this.

edit:
Phil, I apologize to you for the haranguing on your thread. There is a great deal of information in the forum archives on this problem. Your boat, your choice, the solution is ultimately up to you. Best of luck.

[hanleyclifford]

Does anyone know what is the minimum amperage that will fire the coil and run an A4?

[romantic comedy]

this is all covered by a simple linear relationship:

E=IR, which says that voltage equals amps times resistance.

Amps=volts divided by resistance.

It seems simple to me:
You get a coil that has resistance, what ever that is.
You have an alternator that has a voltage, whatever that is.

Plug these into the equation, and you find the amperage.
If it is over 4 amps, you add resistance by adding a resistor.

[ndutton]

Does anyone know what is the minimum amperage that will fire the coil and run an A4?

Why would you ask such a loaded question when you know amperage is not a stand-alone factor? C'mon, this forum is better than that.

RC, yes it's as simple as that, has been all along. Don't forget to build in a safety cushion. It's risky designing to the ragged edge.

[hanleyclifford]

this is all covered by a simple linear relationship:

E=IR, which says that voltage equals amps times resistance.

Amps=volts divided by resistance.

It seems simple to me:
You get a coil that has resistance, what ever that is.
You have an alternator that has a voltage, whatever that is.

Plug these into the equation, and you find the amperage.
If it is over 4 amps, you add resistance by adding a resistor.

But where does the 4 amps number come from? I suggest that the A4 will run on less.

[hanleyclifford]

Why would you ask such a loaded question when you know amperage is not a stand-alone factor? C'mon, this forum is better than that.

You are sounding rather authoritative (authoritarian?) tonight, Neil. The question is a reasonable one. I know from many years of hot rodding and working on engines that no increase in performance comes from increasing an already adequate spark. At 6 to 1 compression do we really need 4 amps?

[romantic comedy]

Good question Hanley. I thought that the 4 amps was an "accepted limit".
Maybe not?

Also, I am making it a bit simpler then it actually is. I just dont want to get into more advanced concepts when this way would work just fine in calculating the current.

It is about making spark, and could be considered independent of the engine. The accepted 4 amps, I understand, is the upper limit of current for the battery-coil system. As long as the spark is made and the engine runs at a lower current, it would work fine.

Is longevity an issue? Would a coil have a shorter, and less reliable life at 4 amps versus less? I dont know, do we have data on this issue?

[hanleyclifford]

Good question Hanley. I thought that the 4 amps was an "accepted limit".
Maybe not?

Also, I am making it a bit simpler then it actually is. I just dont want to get into more advanced concepts when this way would work just fine in calculating the current.

It is about making spark, and could be considered independent of the engine. The accepted 4 amps, I understand, is the upper limit of current for the battery-coil system. As long as the spark is made and the engine runs at a lower current, it would work fine.

Is longevity an issue? Would a coil have a shorter, and less reliable life at 4 amps versus less? I dont know, do we have data on this issue?

I do. I have run the same coil for 20 years including 7 round trips to Florida. I run 10 to 12 hours a day and I like a cool coil that I can put my hand on. I have been repaid.

[romantic comedy]

It is all about what works and reliability. You have got that down.
My engine has the original coil, as far as I can tell. It gets pretty hot. I have often wondered how hot, and what the current is. I just never got around to measuring it. It keeps going. I have 3 spare coils aboard, just in case.

I have thought of going with the electronic ignition, but dont see the need. My access is great. The engine is in the middle of the cabin. I ran the ICW from Annapolis to Florida. Great trip.

I keep threatening to do it again. Maybe come see you Hanley.

[hanleyclifford]

It is all about what works and reliability. You have got that down.
My engine has the original coil, as far as I can tell. It gets pretty hot. I have often wondered how hot, and what the current is. I just never got around to measuring it. It keeps going. I have 3 spare coils aboard, just in case.

I have thought of going with the electronic ignition, but dont see the need. My access is great. The engine is in the middle of the cabin. I ran the ICW from Annapolis to Florida. Great trip.

I keep threatening to do it again. Maybe come see you Hanley.

I am going to add an ammeter for coil+ ---just to put this argument to rest.

[hanleyclifford]

It is all about what works and reliability. You have got that down.
My engine has the original coil, as far as I can tell. It gets pretty hot. I have often wondered how hot, and what the current is. I just never got around to measuring it. It keeps going. I have 3 spare coils aboard, just in case.

I have thought of going with the electronic ignition, but dont see the need. My access is great. The engine is in the middle of the cabin. I ran the ICW from Annapolis to Florida. Great trip.

I keep threatening to do it again. Maybe come see you Hanley.

See your PM box.

[ndutton]

Okay, another round.

• The 4 amp number comes from the manufacturer of our typical electronic ignition, Pertronix and is a maximum. Nobody suggested we need 4 amps to function but rather that the manufacturer specifies their product should not be subjected to greater than 4 amps. This has been clearly stated time and time again, as recently as post #16 in this thread only a few hours ago. Why is it still in question?
• About your question of how many amps to get a coil to produce spark, we can get a coil to produce spark with a fraction of an amp but it will take longer for the coil to reach saturation, a minimum amount of voltage being present. The amperage factor affects the time it takes for the coil to reach saturation, not if it will. The question was a misdirection because it has nothing to do with Phil's shutdown problem, the subject of this thread.
• Why the continued avoidance, resistance if you will (pun intended), of the extensive studies performed here with a proven track record? It matters not who did it but that it was done, resolved, solution reached and applied successfully. I cannot understand the motivation.
• Still avoiding my 9 volt example?
• Again, sorry Phil and others but it's painfully obvious I've had it up to here with this constant obfuscation of a resolved issue. Time for a sabbatical.

[BadaBing]

t I 1.5Ω e (there are 3/4Ωest of luck.

I for one greatly enjoyed reading that very long thread on coils. From it I learned several things.
If you use EI amperage is a coil eater, normally because our alternately are so much better than they used to be.
To solve the "problem" the simplest way is to buy the correct coil.for the EI system you using. If you have an EI from MM it will work nicely and reliable with the coil sold by MM for the EI.
If you choose not to run the prescribed coil then it is wise to stay With points. Which is what I have thus far done because other necessary parts depleted the banal a tad for now.
I also learned, from reading that thread that their is room for those who want to tinker to make a square peg fit into.a.round hole. Some do it so well and with such grace that it makes less qualified wannabes, like me, "think" it's worth trying. Sometimes it's is. Sometimes that trying to save $50 ends up costing much much more in time and $ and then I end up going back,sometimes, and following the recommended advice that I should have from.the start.

Just one question.
How do you make you make the ohms sign? Do you use a Greek letter ?

Btw
Thanks to You Guys who have been sorting all of this.out and sharing it with us who are trying to.