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Spark plug wire resistance theory fact or fiction?

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Spark plug wire resistance theory fact or fiction?

ledopmi ledopmi
New User | Posts: 13 | Joined: 10/06
Posted: 10/23/06
06:19 AM

I have been looking for low resistance wires for my car, since I have seen two dyno tests where the Granatelli wires, at less than one ohm per foot, showed a horsepower gain on the dyno. In the process of researching wires, I came across this:


By far the most popular conductor used in ignition wires destined for race and performance street engines are spiral conductors (a.k.a. mag, pro, super, spiral, monel, heli, energy, ferro, twin core etc.). Spiral conductors are constructed by winding fine wire around a core. Almost all manufacturers use constructions which reduce production costs in an endeavor to offer ignition component marketers and mass-merchandisers cheaper prices than those of their competitors.

In the USA in particular, most marketers of performance parts selling their products through mass-merchandisers and speed shops include a variety of very effective high-output ignition systems together with a branded not-so-effective ignition wire line using a spiral conductor. Most perpetually try to out-do their competitors by offering spiral conductor ignition wires with the lowest electrical resistance. Some publish results which show their wires are superior to a competitor's wires which use identical cable (on which another brand name is printed). The published "low" resistance (per foot) is measured with a test ohmmeter's 1 volt direct current (DC) passing through the entire length of the fine wire used for the spiral conductor.

"Low-resistance" conductors are an easy sell, as most people associate all ignition wire conductors with original equipment and replacement ignition wire carbon conductors (which progressively fail as a result of microscopic carbon granules burning away and thus reducing the spark energy to the spark plugs) and with solid wire zero-resistance conductors that were used by racers with no need for suppression. Consumers are easily led into believing that if a spiral conductor's resistance is almost zero, its performance must be similar to that of a solid metal conductor all race cars once used. HOWEVER, NOTHING IS FURTHER FROM THE TRUTH!

What is not generally understood (or is ignored) is that as a result of the laws of electricity, the potential 45,000 plus volts (with alternating current characteristics) from the ignition coil (a pulse type transformer) does not flow through the entire the length of fine wire used for a spiral conductor like the 1 volt DC voltage from a test ohmmeter, but flows in a magnetic field surrounding the outermost surface of the spiral windings (skin effect). The same skin effect applies equally to the same pulsating flow of current passing through carbon and solid metal conductors.

A spiral conductor with a low electrical resistance measured by an ohmmeter indicates, in reality, nothing other than less of the expensive fine wire is used for the conductor windings — a construction which cannot achieve a clean and efficient current flow through the magnetic field surrounding the windings, resulting in poor suppression for RFI and EMI.

Of course, ignition wire manufacturers save a considerable amount in manufacturing costs by using less fine wire, less exotic winding machinery and less expertise to make low-resistance spiral conductors. As an incentive, they find a lucrative market amongst performance parts marketers who advertise their branded ignition wires as having "low-resistance" conductors, despite the fact that such "low-resistance" contributes nothing to make spiral ignition wires perform better, and RFI and EMI suppression is compromised.

In recent years, most ignition wire manufacturers, to temporarily improve their spiral conductor's suppression, have resorted to coating excessively spaced spiral windings, most of which are crudely wound around strands of fiberglass or Kevlar, with a heavy layer of high-resistance carbon impregnated conductive latex or silicone compound. This type of construction hides the conductive coating's high resistance when the overall conductor is measured with a test ohmmeter, which only measures the lower resistance of the sparse spirally wound wire (the path of least resistance) under the conductive coating and ignores the high resistance of the outermost conductive coating in which the spark energy actually travels. The conductive coating is rarely shown or mentioned in advertisement illustrations.

The suppression achieved by this practice of coating the windings is only temporary, as the spark current is forced to travel through the outermost high-resistance conductive coating in the same manner the spark current travels through the outermost high-resistance conductive coating of a carbon conductor used in most original equipment and stock replacement wires.

In effect, (when new) a coated "low-resistance" spiral conductor's true performance is identical to that of a high-resistance carbon conductor.

Unfortunately, and particularly with the use of high-output ignitions, the outermost high-resistance conductive coating over spiral windings acting as the conductor will fail from burn out in the same manner as carbon conductors, and although in most cases, the spiral conductor will not cease to conduct like a high-resistance carbon conductor, any RFI or EMI suppression will be lost as a consequence of the coating burning out. The worst interference will come from the so-called "super conductors" that are wound with copper (alloy) wire.

However, despite the shortcomings of "low-resistance" spiral conductor ignition wires, these wires work satisfactorily on older production vehicles and race vehicles that do not rely on electronic engine management systems, or use on-board electronics effected by EMI — although with the lowest-resistance conductor wires, don't expect much RFI suppression on the AM band in poor reception areas.

Some European and Japanese original equipment and replacement ignition wires including Bougicord and NGK do have spiral conductors that provide good suppression — usually none of these wires are promoted as having low- resistance conductors — however, none are ideal for competition use, as their conductors and pin-type terminations are fragile and are known to rarely last as long as good carbon conductor ignition wires.

To be effective in carrying the full output from the ignition system and suppressing RFI and EMI in particular, spiral conductors need windings that are microscopically close to one another and precisely spaced and free from conductive coatings. To be more effective, the windings need to be wound over a core of magnetic material — a method too costly for wires sold through mass-merchandisers and most speed shops who purchase only the cheapest (to them) and most heavily promoted products.

Claims of Horsepower Gain

Every brand of spiral conductor ignition wires will perform the function of conducting coil output to the spark plugs, but NONE, despite the claims made in advertisements and other promotional literature, will increase horsepower. Independent tests, including a test performed by Circle Track Magazine (see May, 1996 issue) in the USA, show that NO "low-resistance" ignition wires for which a horsepower increase is claimed do in fact increase horsepower - the test also included comparisons with solid metal and carbon conductor ignition wires.

Are these guys correct?  If so, then how do we explain a Corvette and a Chevy truck gaining over 10 hp with nothing more than a plug wire change?
I was looking at buying a set of MSD wires that are only 50 ohms per foot.  I am sending back a set of Crane Fire Wire because they claimed to be 25 ohms per foot and I measured 550-850 ohms.   This is double what my factory wires measure! These are short LS1 wires so they should have been about 12 ohms, not 550-850.
After reading what Magnacor says, I am not sure what to do.  

Duvorack Duvorack
New User | Posts: 2 | Joined: 04/08
Posted: 04/24/08
04:26 AM

I did a write up about plug wires at a honda forum.  Magnacore wires are BS and they only post up what is good for themselves, much like any otehr company.  I doubt that they amke anything more special than a "pretty" stock wire for any car.

I would love to get a set of every "name brand" wire out there and dyno them all 3x and average every brands result, but I can't.

I would build my own from solid copper core wire but I don't have the time or equipment right now.  

lothar lothar
New User | Posts: 2 | Joined: 06/08
Posted: 06/23/08
04:28 AM

Well it's a good thing that you don't have the time to build your copper wires because it would just be a waste of materials.

It's pretty apparent from your post that you have little understanding with respect to the transmission of EM pulses in (on) a conductor.

The superhonda write up is pretty much nonsense; trying to draw an analogy between the transmission of AUDIO FREQUENCY signals in a speaker wire and an EM pulse on a spark plug wire is ample proof that you are in over your head here.  

lothar lothar
New User | Posts: 2 | Joined: 06/08
Posted: 06/23/08
04:35 AM

"Are these guys correct?  If so, then how do we explain a Corvette and a Chevy truck gaining over 10 hp with nothing more than a plug wire change?"

Standard carbon wires arc and burn. The horsepower gain was seen because faulty wires were replaced with new ones.

The late Joe Matthews, of GM Engineering told me that a factory wire set was good for about 1 year.

Standard carbon plug wires should be thought of as a consumable item.  

4x4Wheels 4x4Wheels
New User | Posts: 1 | Joined: 06/08
Posted: 06/30/08
08:16 PM

For me thats a lot of horse power by just changing the plug wire (?) I never knew that one before...

Have you heard about Pulstar Plugs???  Confused  

waynep712 waynep712
New User | Posts: 11 | Joined: 06/08
Posted: 06/30/08
10:42 PM

not only do spark plug wires go bad....

but spark plugs also go bad... and can slow a car down...

so swap out  your spark plugs every few runs... or as soon as you see a few tenths unexplained drop in ET's ...

there is no reason for it... it just does happen...

back to spark plug wires...

when the electrons get sent down the wires they tend to burn the carbon out...

i have found oem wires that had the carbon burned all the way out... i wondered why the car would just barely run...

a little theory...  when the magnetic field in the primary winding collapses.. the voltage in the secondary raises until it can complete a circuit to ground..

the ground is usually back in the dizzy housing..  so the spark goes out the coil wire... through the cap, through the rotor... jumps the gap to the cap again.  out the spark plug wires... through the spark plug and across the gap.. through the head... into the block or intake which ever has the dizzy hold down ,..

people have taken to grounding both heads to the dizzy housing. to complete the circuit... instead of just depending on the head bolts or intake bolts and the dizzy hold down...

everybody needs to examine their external frame coils...   look at the sides of the windings near the frame for circular powder marks.. or discolorations.  

this is an indicator high voltage leakage from the coil...  this happens a lot...
since engines require more voltage to fire the plugs under heavy loads it just leaks out the side instead of going the long way to ground...

same thing for rotors...  they burn through the bottom...

little black plastic coil out put voltage testers are available in most parts stores tool isles...   they have a 1/4-20 screw with a ground clip spot welded to the end.. and a place to put a  spark plug wire on the other end... the inside has a scale on it..      you open the gap more and more until the spark no longer jumps the gap... then you know how much you really have...  

and please don't try changing the gap while the engine it cranking..   Zap Crackle Pop!!!!!!  

Duvorack Duvorack
New User | Posts: 2 | Joined: 04/08
Posted: 08/14/08
09:17 PM

Originally posted by Lothar:
"It's pretty apparent from your post that you have little understanding with respect to the transmission of EM pulses in (on) a conductor.

The superhonda write up is pretty much nonsense; trying to draw an analogy between the transmission of AUDIO FREQUENCY signals in a speaker wire and an EM pulse on a spark plug wire is ample proof that you are in over your head here."

ANYWAYS, I used the speaker reference as an easy to understand example for people who dont quite grasp electronics.

The EM pluses that a stock ignitions system can produce on a solid copper wire is pretty weak, its not like people are using a coil with an solid iron core cranking 100 amps through it.

Magnacore sucks, they try to slander lower resistance wires which last generally last longer and perform better than theirs with such nonsense as "skin effect".

The fact is that the lower the resistance the better the spark you will achieve.  Suppressing RFI/EMI is extremely easy.  Copper foil + ferrite core easily deals with the small wattage of ignition system.  Its not like its a damn broadcasting station for Radio waves.

Not only that but the biggest problem originally with running 0 ohm soild strand wires was AM radios where FM radios aren't affected as much.  This was commonly solved with putting a filter, IE a choke on your CB/AM radio.  Besides an altornator would pose a larger problem than some spark plug cables considering its duty and amps.  This is why incorrectly installed car audio systems get the alternator whine.

I'll be building my own spark plug cables in the next few months as well, by reusing some of the componets of the old stock wires.  

Granatelli Granatelli
New User | Posts: 1 | Joined: 02/13
Posted: 02/05/13
02:48 PM

I know it’s late but I just came across this.  Now years later and still The GMS 0 ohm wires are the only ones still making power that can be measured on the dyno back to back and increased MPG.  It does this for all the reason even the competition mentions above.  Why because we have the technology to get 100% of the outputted voltage tot he plug with out any EMI or RFI vie our patented suppression system  

Serpico Serpico
New User | Posts: 1 | Joined: 02/13
Posted: 02/06/13
12:06 PM

Back in the day before all the electronic controllers, we ran solid core wires. They worked well and we had antennas for tv reception, when we came near anyone that had a tv antenna, it screwed up the reception until we shut the engine off. If we had a mag it was even worse. I use to get blasted with the open ends.

Bob  AKA pepsi1