Post your spark plug wire brand and resistance here...
Originally Posted by joecar
Very good point 
, and a VOM/DMM/Ohm-meter measures only resistance and not reactance ,and can't measure if the insulation is bad/broken.
(BTW: when measuring wire resistance, the wire should be flexed and rolled back and forth, since this will/may show any 'intermittent' type of breaks in the core.)
, and a VOM/DMM/Ohm-meter measures only resistance and not reactance ,and can't measure if the insulation is bad/broken.(BTW: when measuring wire resistance, the wire should be flexed and rolled back and forth, since this will/may show any 'intermittent' type of breaks in the core.)
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From: So.Cal.
Originally Posted by cantdrv65
The best way I have found to test for a faulty plug wire is put the car in high gear and lug the engine. Or just reach around in the engine bay until you get the **** knocked out of yourself(more of an accidental approach).
a meter is sufficient to simply check the resistance of a conductor. i.e. plug wire. to test the insulating properties of the protective covering a megohmmeter or megger should be used.
not trying to disagree with anyone...
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
oh, and my MSD wires were all ~43-44ohms.
not trying to disagree with anyone...
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
oh, and my MSD wires were all ~43-44ohms.
A friend and I tested a set of msd wires and checked them at about 45 ohms. Just for the heck of it, he tested a wire off of his restored H Farmall tractor, restored in the 70's, and those wires tested 9 ohms.
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Originally Posted by Okie5.3
not trying to disagree with anyone...
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
properties within the ignition wires of an automobile because it's a DC charge?
Last edited by Adrenaline_Z; May 28, 2006 at 01:52 PM.
using MSD wires for example. there is no measureable amount of capacitance in these wires. reason is the two bare copper conductors are tightly twisted together without the use of any dielectric material. twist together the same copper conductors with insulation material on each one and you may have capacitance depending on how much (length) is twisted together.
to verify any capacitance of an MSD wire, take a meter set it to read resistance and measure across the wire. if there is any capacitance the meter would go from no or low resistance and slowly climb to infinity. if it does you have capacitance, if not you don't.
as far as inductive properties of spark plugs wires, depends. using the MSD wires as an example again. the same two bare copper conductors are not twisted around a piece of ferrite, so any amount of XL would also be insignificant. this could also be verified with a meter using the resistance setting. an inductor would read infinity initially and drop to read low or no resistance.
more than likey in the case of the spark plug wires there is a X=0 state, meaning XC and XL are equal therefore leaving a purely resistive circuit.
to verify any capacitance of an MSD wire, take a meter set it to read resistance and measure across the wire. if there is any capacitance the meter would go from no or low resistance and slowly climb to infinity. if it does you have capacitance, if not you don't.
as far as inductive properties of spark plugs wires, depends. using the MSD wires as an example again. the same two bare copper conductors are not twisted around a piece of ferrite, so any amount of XL would also be insignificant. this could also be verified with a meter using the resistance setting. an inductor would read infinity initially and drop to read low or no resistance.
more than likey in the case of the spark plug wires there is a X=0 state, meaning XC and XL are equal therefore leaving a purely resistive circuit.
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From: Mefis
Have you guys heard of how Harley Davidson measures detonation in their twin cam engines?
From what I have heard, they use a secondary voltage across the spark plug and measure the resistance. That will tell them the cylinder pressure and therefore if knock is present. So then would aftermarket wires on these engines affect the detonation measuring capabilities?
From what I have heard, they use a secondary voltage across the spark plug and measure the resistance. That will tell them the cylinder pressure and therefore if knock is present. So then would aftermarket wires on these engines affect the detonation measuring capabilities?
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From: K-W, Ontario
Originally Posted by Okie5.3
using MSD wires for example. there is no measureable amount of capacitance in these wires. reason is the two bare copper conductors are tightly twisted together without the use of any dielectric material. twist together the same copper conductors with insulation material on each one and you may have capacitance depending on how much (length) is twisted together.
the plug is a break in the DC circuit; the air and fuel pressurized within the
cylinder in the insulator. You now have a potential difference between the
electrodes, and any residual charge remaining that cannot jump the gap,
stays in the wire creating stored energy as a capacitor would.
Originally Posted by Okie5.3
to verify any capacitance of an MSD wire, take a meter set it to read resistance and measure across the wire. if there is any capacitance the meter would go from no or low resistance and slowly climb to infinity. if it does you have capacitance, if not you don't.
not produce a rising and falling field like the charging and discharging energy
of the coil. The meter also does not produce a frequency of pulsing DC. As
the RPM of the motor increases, so will the frequency of the pulsations.
Originally Posted by Okie5.3
as far as inductive properties of spark plugs wires, depends. using the MSD wires as an example again. the same two bare copper conductors are not twisted around a piece of ferrite, so any amount of XL would also be insignificant. this could also be verified with a meter using the resistance setting. an inductor would read infinity initially and drop to read low or no resistance.
the energy get into the wire? Think of how a transformer operates, it's an
inductive process. Since the secondary field winding is connected to the
spark plug wire, the voltage is also induced into the wire at the time the
secondary winding is charged (coil pack); or once the rotor reaches the spark
plug post (distributor).
Originally Posted by Okie5.3
more than likey in the case of the spark plug wires there is a X=0 state, meaning XC and XL are equal therefore leaving a purely resistive circuit.
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From: So.Cal.
Originally Posted by Okie5.3
a meter is sufficient to simply check the resistance of a conductor. i.e. plug wire. to test the insulating properties of the protective covering a megohmmeter or megger should be used.
not trying to disagree with anyone...
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
oh, and my MSD wires were all ~43-44ohms.
not trying to disagree with anyone...
but unless there is some sort of insulator (dielectric) between the conductors (twisted wires), there cannot be any capacitance, which is demonstrated by measuring the resistance of the spark plug wire using a dc powered meter. capacitance reactance (Xc) resists DC current flow, therefore would indicate an open when measured with a dc powered meter.
also since the conductors generally are not twisted around an iron core of some sort, and the voltage produced by the coils resembles AC current, would rule out inductance. an inductor resists, or chokes out AC current, but allows DC current to flow. the amount of resistance an inductor has to AC current is directly proportional to the frequency of the signal.
this would then lean towards more of a purely resistive circuit.
oh, and my MSD wires were all ~43-44ohms.
A megger would output upto about 1kV-2kV, whereas the ignition coils output somewhere from 30kV-50kV; can a megger reach this voltage...?
I don't follow regarding the twisted wires...?
The plug wire contains a single conduction path, either a carbon impregnated filament, or a conductor spirally wound around a ferrite impregnated core, so I missed what you said.
The capacitance mentioned previously is due the gap at the spark plug (with air:fuel mixture as the dielectric).
Edit: An it can't be a purely resistive circuit because the coil (which is a massive inductor) is in series.
Edit: Adrenaline beat me on the response...
ok, i think understand how you guys are looking at this.
you are equating the gap in the spark plug, with the air/fuel being the insulating (dielectric) material opposing current flow, to basically what an air core capacitor would be. the spark is derived from the sudden voltage increase from the coil charging, creating a difference of potential at the electrode and ground strap, which becomes so great it charges (ionizes) the free electrons in the immediate vicinity making them conductive, creating a path to ground for current flow discharging the built up energy from the coil and making a spark. whereas the difference in a capacitor, there is current flow until the capacitor is charged, and the energy from that difference of potential is not released across the plates when discharging, but rather reverses path and flows in the opposite direction.
i was looking at it from a different perspective, but i gotcha now.
you are equating the gap in the spark plug, with the air/fuel being the insulating (dielectric) material opposing current flow, to basically what an air core capacitor would be. the spark is derived from the sudden voltage increase from the coil charging, creating a difference of potential at the electrode and ground strap, which becomes so great it charges (ionizes) the free electrons in the immediate vicinity making them conductive, creating a path to ground for current flow discharging the built up energy from the coil and making a spark. whereas the difference in a capacitor, there is current flow until the capacitor is charged, and the energy from that difference of potential is not released across the plates when discharging, but rather reverses path and flows in the opposite direction.
i was looking at it from a different perspective, but i gotcha now.
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From: So.Cal.
Originally Posted by joecar
GM stock w/35K miles on the wires, average 357Ω
Taylor Spiro Pro 8.5 mm w/30K miles on the wires, something like 60Ω (I'll go measure it again).
Taylor Spiro Pro 8.5 mm w/30K miles on the wires, something like 60Ω (I'll go measure it again).
6 x 180Ω (average)
1 x 250Ω
1 x 540Ω
I was very careful in removing all 8 wires, so those last 2... go figure...?
The part store is shut today, so I'll just reinstall them till I get new wires.
On The Tree
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From: south of H-ToWn Tx.
I have a slight mis fire and been trying to track it down... What I've found out is MY brand new GMPP red wires Ohm at 370, MY brand new gm black wires LIST $160( out of the bx.) reads 720 Ohm , and my stock ac black wires w/60,000 miles read 350 Ohm... 
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From: So.Cal.
Originally Posted by Zymosis
Stock wires: 365 ohms
MSD: 27 ohms for 7 wires, one was 240k ohms (Piece of **** MSD wires
)
MSD: 27 ohms for 7 wires, one was 240k ohms (Piece of **** MSD wires
)Aren't they guaranteed...? Will they replace your one wire with a good one...?