8N51 Spark plug voltage

Btzj02 · May 21, 2020

Trying to wrap my head around the advantages of a 12 volt system. Has anyone actually measured the voltage at the spark plug wires comparing a 6 volt to a 12 volt system? All the literature indicates, to my in experienced brain, that whether you have a 12 volt or 6 volt system the voltage at the spark plug is basically the same due to resistors on primary side of ignition wiring or a 12 volt coil that is wound to limit the current through the points. Is there any 12 volt system that actually raises the Spark plug voltage significantly above the voltage on the original 6 volt system?

Bruce(OR) · May 22, 2020

MSD for a start on that question.
It is my weak minded understanding that the spark fires from the center to the electrode on 12V neg ground. 6V pos round is the opposite direction. If you up the coil and widen the plug gap you should see an increase in voltage. More oomph needed to jump a wider gap.
More voltage, more power, lower emissions, better mileage. I know you are concerned about mileage and emissions.
Electricity is like most people. Going to do the least amount of energy to get the job done.
All it has to do is jump a .025 gap. Crank the gap up to .045 and the voltage should be going up. 6 or 12V on a .025 gap should not be noticeable. 6V on a .045 gap might not fire the plugs. 12V on a .045 gap will fire. 12V should not have a problem until up around .080 gap.
6V on a .080 gap will not fire.

JMOR · May 22, 2020

(quoted from post at 01:31:07 05/22/20) MSD for a start on that question.
It is my weak minded understanding that the spark fires from the center to the electrode on 12V neg ground. 6V pos round is the opposite direction. If you up the coil and widen the plug gap you should see an increase in voltage. More oomph needed to jump a wider gap.
More voltage, more power, lower emissions, better mileage. I know you are concerned about mileage and emissions.
Electricity is like most people. Going to do the least amount of energy to get the job done.
All it has to do is jump a .025 gap. Crank the gap up to .045 and the voltage should be going up. 6 or 12V on a .025 gap should not be noticeable. 6V on a .045 gap might not fire the plugs. 12V on a .045 gap will fire. 12V should not have a problem until up around .080 gap.
6V on a .080 gap will not fire.

oarity of the spark has NOTHING to do with the 6v or 12v......it is all about how the coil is wired into the system. Next, HV also has little or nothing to do with 6v/12v....the voltage of either will rise to whatever is necessary to arc over the spark gap.

Ultradog MN · May 22, 2020

I've never considered the spark itself as an advantage to 12V.
Both voltages will produce plenty of fire to cause combustion.
It's other things that give 12V a leg up.
Standarization, faster cranking speed and a simpler, more reliable charging system to name a few.

TheOldHokie · May 22, 2020

(quoted from post at 22:18:26 05/21/20) Trying to wrap my head around the advantages of a 12 volt system. Has anyone actually measured the voltage at the spark plug wires comparing a 6 volt to a 12 volt system? All the literature indicates, to my in experienced brain, that whether you have a 12 volt or 6 volt system the voltage at the spark plug is basically the same due to resistors on primary side of ignition wiring or a 12 volt coil that is wound to limit the current through the points. Is there any 12 volt system that actually raises the Spark plug voltage significantly above the voltage on the original 6 volt system?

If it were just that simple. A brief and not overly technical discussion of gasoline engine spark ignition [b:8ad43799a0][u:8ad43799a0]energy[/u:8ad43799a0][/b:8ad43799a0]:

https://www.researchgate.net/publication/322538158_Review_on_performance_of_High_energy_ignition_techniques/link/5a5edd360f7e9b4f783bb8ba/download

You might find the results of approach number 6 mildly interesting.

TOH

Bruce(OR) · May 22, 2020

"Poarity of the spark has NOTHING to do with the 6v or 12v "
Unless you consider the theory of electricity, I believe in my increasing oncoming doddering older age, that says neg flows to positive.
Hence a positive ground system should be different than a Neg ground system.
Untitled URL Link

TheOldHokie · May 22, 2020

(quoted from post at 16:04:39 05/22/20) "Poarity of the spark has NOTHING to do with the 6v or 12v "
Unless you consider the theory of electricity, I believe in my increasing oncoming doddering older age, that says neg flows to positive.
Hence a positive ground system should be different than a Neg ground system.
Untitled URL Link

Read JMOR'S response again - specifically the part you omitted in the quote.

TOH

JMOR · May 22, 2020

(quoted from post at 16:25:07 05/22/20)

(quoted from post at 16:04:39 05/22/20) "Poarity of the spark has NOTHING to do with the 6v or 12v "
Unless you consider the theory of electricity, I believe in my increasing oncoming doddering older age, that says neg flows to positive.
Hence a positive ground system should be different than a Neg ground system.
Untitled URL Link

Click to expand...

Read JMOR'S response again - specifically the part you omitted in the quote
TOH

.editing, omissions, out of context.....just like the 6 o'clock news!

TheOldHokie · May 22, 2020

(quoted from post at 16:53:49 05/22/20)

(quoted from post at 16:25:07 05/22/20)

(quoted from post at 16:04:39 05/22/20) "Poarity of the spark has NOTHING to do with the 6v or 12v "
Unless you consider the theory of electricity, I believe in my increasing oncoming doddering older age, that says neg flows to positive.

Untitled URL Link

Click to expand...

Read JMOR'S response again - specifically the part you omitted in the quote
TOH

Click to expand...

.editing, omissions, out of context.....just like the 6 o'clock news!

And seemingly add to that some confusion about what's happening inside the coil....

"Hence a positive ground system should be different than a Neg ground system."

TOH

Btzj02 · May 22, 2020

Thanks guys I think you all may have indirectly confirmed what I was thinking. I like the 6 volt system but I was trying to learn if a 12 volt system would increase engine performance. After reading what I could find it seemed as though a 12 volt conversion does not impact the energy available at the spark plug. Thus not increasing engine performance. Some information I ran into talked about electronic ignitions that had "Dwell", (black box voodoo magic to me), and other guys that did not install the resistor and then promptly blew the top off there coil. Since I don't plan on installing an 8 Track on the old girl I will stick with the 6 volt system.

8N51 Spark plug voltage

Btzj02

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JMOR

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Ultradog MN

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Bruce(OR)

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