Copper or Carbon Core Wire

[petertay]

Ours is NAA, 6V positive ground. It has Pertronix EI purchased here some years ago. Runs fine.

After reading grandpa Loves discussion about EI where carbon core ignition wires were mentioned, I looked at ours. It is copper wire.

The Pertronix manual doesnt say anything about it. Does copper wire or carbon core matter?

Thanks, Peter

 

[JMOR]

I like to follow this advice, or you may wind up "fixing" it until it IS broke!

 

[Tom in Mo.]

JMOR is 100% correct. I have to tell myself that often.
I believe the carbon core wires were invented to eliminate AM radio interference back in the middle of the last century.

 

[grandpa Love]

I don't know where I got my information.... But I always believed that Ei needs carbon core?? But. If you are running good, leave it alone. Maybe what I read was that a magneto or a distributor with points needs copper core, and the assumption was made about Ei??

 

[Texasmark]

I know there are a lot of engines running carbon core and resistor spark plugs. I guess it doesn't matter whether the energy stored in the coil (1/2 LI exp2) is dumped immediately due to no resistance to extend the discharge time, or over time depending on the series resistance. Last time I checked carbon core wire (decades ago) it was like 5k Ohms......that does extend the discharge time constant.

 

[Texasmark]

The other thing it does is that it allows the discharge to exponentially rise, eliminating the sharp spike, hence high frequency involved with a minimum resistance discharge, that is easily transmitted off the wire and picked up by the radio. Since Joules of energy are dissipated in the heat of the spark, and since discharge time is vs engine RPM, not RPS, it matters not....apparently so, it works!

 

[JMOR]

(quoted from post at 06:57:35 05/31/23) I don't know where I got my information.... But I always believed that Ei needs carbon core?? But. If you are running good, leave it alone. Maybe what I read was that a magneto or a distributor with points needs copper core, and the assumption was made about Ei??

have read several Pertronix installation instruction sheets (not all), but my conclusion is that they state "do not use solid core spark plug wires" with[u:94e5afe64a] Ignitor II.[/u:94e5afe64a]. This statement is NOT on the installation instruction sheets with the [u:94e5afe64a]Ignitor,[/u:94e5afe64a] which is what is used on these old tractors. Ignitor II does NOT seem to be available for these old tractors, just for higher performance vehicles. The "II" is key.

 

[jimtrs]

The Pertronix Ignitor II Kits, seem to be available, only for 12 Volt Negative ground systems


from Pertronix website:

Ford Front Mount
91247
Pertronix Ignitor II Kit For Original Ford Front Mount Distributors. 8-Cylinder, Single Point, 12-Volt Negative Ground. Typically Found In 1939-50 2N & 9N Ford Tractors.
(the reference to 8-cylinders, seems to be a typo)

Ford Side Mount
91244A
Pertronix Ignitor II Kit For Original Ford Distributors. 4-Cylinder, Single Point, 12-Volt Negative Ground. Typically Found In Ford Tractors Models 8N, 500 Through 800 Series.

 

[JMOR]

(quoted from post at 13:54:47 05/31/23) The Pertronix Ignitor II Kits, seem to be available, only for 12 Volt Negative ground systems


from Pertronix website:

Ford Front Mount
91247
Pertronix Ignitor II Kit For Original Ford Front Mount Distributors. 8-Cylinder, Single Point, 12-Volt Negative Ground. Typically Found In 1939-50 2N & 9N Ford Tractors.
(the reference to 8-cylinders, seems to be a typo)

Ford Side Mount
91244A
Pertronix Ignitor II Kit For Original Ford Distributors. 4-Cylinder, Single Point, 12-Volt Negative Ground. Typically Found In Ford Tractors Models 8N, 500 Through 800 Series.

ood info, but an aside, as the man was asking about 6 volt system that he has. Thanks anyway.

 

[MarkB_MI]

I just went to the Pertronix site and downloaded the instructions for the Pertronix 1244AP6, which is what I believe you have. You're right, it doesn't say anything about resistance plug wires. But most other Pertronix instructions are adamant that resistance wires must be used.

Here's the deal: The high-voltage, high-frequency spikes in an automotive ignition system are rough on solid-state switches. Resistance plug wires help to suppress those spikes by absorbing a little bit of energy. Failure of a solid-state switch from voltage spikes is typically not instantaneous; it can take many hours of operation before the switch eventually fails. Yes, yours has operated for a long time and will probably go a lot longer. But if it was my tractor, I'd look for resistance wires. The OEM wires from CNH should be resistance.

 

[JMOR]

"But most" Ignitor II "Pertronix instructions are adamant that resistance wires must be used". I do believe is more accurate.

 

[Texasmark]

Yes on absorption but the real reason is that when the switch closes, since the resistance prevents the current from instantly surging causing high voltage.....V = L di/dt where di is max and dt is min you get the steep rising, high voltage spike. By adding the resistance, di is spread out over the time constant at an exponential rate, preventing both the spike and the amplitude.......this is a moot point but being retired for 18 years, with the brain thing, use it or lose it....and its going fast.

 

[Texasmark]

Added comment: The good news is that the lack of resistance in the bare wire allows the fast rising spike which, like Mercury Marine's advertised unloaded microsecond rising 40kV pulse, it gets the bang to semi-fouled/fouled plugs and gets them fired before the contaminants have time to bleed off the energy contained in the pulse.......ALA like old farm tractors and worn out trucks. So that may explain why some OEMs say to use solid core wires.....besides I never could hear my radio over tractor noises anyway so its a moot point also.

 

[JMOR]

10-4 Texasmark

 

[sotxbill]

I'm confused here... An charged inductor will discharge based on the resistance of the circuit. A circuit with high resistance will see a HIGHER VOLTAGE, that a circuit with a lower resistance. Yes we have the resistance of the air gap plus the resistance of the plug wire. A copper wire has almost zero resistance. A carbon wire can have up to 40k ohms per foot. The same coil will discharge at a higher voltage with carbon wires than copper wires. Thus it can over come slightly fouled plugs and actually self clean them. Higher voltage also means the initial current will be higher vs a lower voltage, all other things being equal. Higher voltage will mean a hotter spark and jumps a bigger gap. Bigger gap means quicker combustion, more complete combustion and cyl flame pattern, more power delivered in all tests over small gaps.

An inductor will have a higher voltage on discharge with higher resistance. A capacitor will have a higher voltage on discharge with lower resistance in the circuit. I realize my 1971 college engineering electronics is a bit dated but did something change? High resistance plug wires should raise the initial voltage and therefore the initial current in t1 of the 5 time constants normally computed. And since the charge cycle is done on the primary side, its not slowed down by the secondary resistance changes.

 

[Sean in PA]

(quoted from post at 11:20:07 06/03/23) I'm confused here... An charged inductor will discharge based on the resistance of the circuit. A circuit with high resistance will see a HIGHER VOLTAGE, that a circuit with a lower resistance. Yes we have the resistance of the air gap plus the resistance of the plug wire. A copper wire has almost zero resistance. A carbon wire can have up to 40k ohms per foot. The same coil will discharge at a higher voltage with carbon wires than copper wires. Thus it can over come slightly fouled plugs and actually self clean them. Higher voltage also means the initial current will be higher vs a lower voltage, all other things being equal. Higher voltage will mean a hotter spark and jumps a bigger gap. Bigger gap means quicker combustion, more complete combustion and cyl flame pattern, more power delivered in all tests over small gaps.

An inductor will have a higher voltage on discharge with higher resistance. A capacitor will have a higher voltage on discharge with lower resistance in the circuit. I realize my 1971 college engineering electronics is a bit dated but did something change? High resistance plug wires should raise the initial voltage and therefore the initial current in t1 of the 5 time constants normally computed. And since the charge cycle is done on the primary side, its not slowed down by the secondary resistance changes.

My high school electronics courses may not have been as advanced as yours in college, but a coil is a transformer, and it was my understanding that the output voltage of a transformer is directly related to the input voltage to the primary and the ratio of windings between the primary and secondary, so if the primary winding is being given a particular input voltage spike, the voltage at the secondary will always be a multiple of the input voltage based on the ratio of the windings. What does the resistance of the circuit connected to the secondary have to do with the voltage that the secondary will provide? The resistance of the circuit should only affect the current drawn from the specific voltage, not the voltage itself.

 

[Texasmark]

Thanks J! Glad I got it right. Grin

 

[Texasmark]

Sir it's all right here: V-L di/dt per the L/R exponential time constant. The L essentially blocks initial current so the current starts at essentially zero and rises exponentially to the max value determined by the resultant voltage and circuit resistance.

The voltage across the coil doesn't fire the plugs. If you have voltage but no current you haven't dissipated any energy. The stored energy in the coil is what fires the plug and the circuit current is what gets that energy to the plug. Therefore with no resistance, considering the inductance value L, the current gets to the plug fast, builds up voltage across the gap because it's blocked (high R at the plug) the voltage continues to rise and bang, the gap breaks down into a VR plasma and you have a current impulse....... for the length of dt.
Putting resistance in the circuit slows down this delivery mechanism preventing the sharp current discharge spike. Is there voltage developed across resistance wire during this discharge, of course......you have R and current flowing through it.

 

[Texasmark]

Rewording the voltage doesn't fire the plug. obviously it causes the gap to break down and start conducting current creating the gap plasma (VxI) that dissipates the energy from the coil.

 

[Hobo,NC]

For your application a quality carbon core wire installed correctly will get'er done and be more than adequate for the job of delivering the voltage needed to jump the resistance of the spark plug gap fuel mixture in the cylinder.

Issues will arise from a poor quality parts and the job of making a custom set of spark plug wires for you ignition. Your round can coil will be happy as most any coil as long as you don't ask it to perform at a constant higher level than it was designed for.

Your pertronix will be happy as well.

In my lifetime it would be a rare event to see a new engine design that would required a copper core spark plug wire. Unless it is a specific issue required let those copper core plug wires go.