Conference vmsnet::car$note:carbuffs

    I have been trying to do some comparison of ignition wires.  I have
    been looking at MSD, Mallory, Moroso, Accel, Splitfire, and something
    else that slipped my mind at the moment.  According to the
    manufacturer's info, everybody has the best wires, and all make some
    good sounding claims.  The one that looked the best to me on paper was
    the MSD 8.5mm Superconductor wires.  They claim 40-50 ohms per foot
    resistance, which is supposedly the lowest resistance in the industry.
    They are wound copper conductors on a fiberglass core.  I also have a
    coworker who is strongly recomending the Splitfire wires.  I'd like to
    get some opinions as to who's wires are really the best.  I also saw an
    earlier note stating that the 8+mm wires may not fit the caps on
    earlier (non hi-energy ignition) cars; is this an issue on the early GM
    distributor caps?
    
    Dave

    The "best" wires?  Or wires that work for your application.
    
    I use Moroso Blue Max 8mm spiral core wires in my Camaros.  They
    work great.  I use Accel Extreme 9000 wires in my truck because
    the wire routing gets very close to my headers.
    
    You don't want wires that will cause inductive crossfire.  You do
    want wires with the least resistance in order to deliver as much
    voltage to your plugs as possible.  If you listen to the radio, you
    want to make sure the wire is shielded.
    
    All wires carry voltage to the plugs.  How well they last and how
    much voltage gets to the plug makes the difference.
    Also, the boot angle is important.
    
    Some real world experience now:
    You want a good ignition, get a CD box (Mallory or MSD).  Spending
    a lot of money on spark plug wires is a waste.  Spend $30 for the
    blue max wires and $100 for the box and go like hell.  The $30 wires
    will handle the improvements from the box.
    
    I mention this because you mention a vendor by name who's wires
    are probably more expensive that you need to spend.  Making the
    spark plug fire good makes power.
    
    HEI and Non-hei plugs are different.  In some cases you can use
    a shrink shield to fit the wire to the cap, but if your worried about
    who makes the best and checking ohm resistance and stuff, buy
    the proper fitting wires up front.
    
    MadMike  

    Also, since you don't have an HEI ignition, you may be able to
    soup up your ignition with a better coil or an inductive discharge
    system.
    
    The point I was making before was the wire takes the voltage from
    the ignition to the plugs.  You can spend a bunch on wires, but not
    be sending enough voltage to the plug (at least to justify super
    wizbang plug wire).
    
    When your ignition system has the ability to turn off your neigbors
    appliances, then you may need to evaluate specific wire vendor
    claims.
    
    MadMike

    I probably should have given a little more info.  I do plan to upgrade
    to a CD box (but maybe not imediately) so thanks for offering that info
    even though I didn't ask for it.  I have bought a couple of sets of
    cheap wires in the past and regreted it.  I had one go completely open
    after only about 6 months.  The car came with a set of Super Stock 
    (entry level Excel) wires on it, and when I went to remove them, a
    couple of the crimps separated from the wires and stayed on the plugs.
    I have just had it with cheap stuff.  What I'm liiking for here is
    quality.
    
    Dave

    Quality:
    Blue max's haven't failed on me in years.
    The extreme 9000's, a couple are less than 1/2 inch from a header tube
    and the wire isn't damaged.  It's been that way since last may.
    
    Blue max = $35 - 50.  
    
    I didn't want to help someone spend $$$ without discussing the big
    picture.  You know... some folks (not you of course) would ask about the
    idea of buying a magneto for a chevette or something....
    
    MadMike

Don't buy an MSD.  If you want a history of the problems I and others have 
had with MSD ignitions, send me mail (before I go on vacation next 
Thursday)

Suffice it to say, a few of us have had multiple (repeated) catastrophic 
failures with MSD boxes, some brand new, right out of the box.

    What is a "good" resistance reading for a carbon core wire?  I was
    checking some out over the weekend, and they were around 7K ohms per
    foot.  The longest wires to the front cylinders were nearly 19K ohms!
    This sounds way high, but then again, I'm not sure what they should be.
    
    Dave 

    Dave,	The average plug wire should have 4000 ohms or less/foot.
    		There are some new wires that are advertising less than
    		500 ohms per foot.
    
    		Replacement is in order with the high readings you hve
    		now!!
    
    						Jack

High resistance is often a deliberate part of the design of the ignition
system.  Don't arbitrarily assume that low resistance is necessarily better.

				Steve

    Jack,
    Thanks.  I thought the reading I was getting sounded way high.  These
    wires look like brand new.  I don't know the actual age since they came
    with the car, but I think they really are fairly new.  I was going to 
    replace them with something better sooner or later, I guess it will be 
    sooner.  As I've learned in the past, it just doesn't pay to buy cheapo 
    stuff.
    
    Dave

    
    I just walked out to my garage and measured some brand new wires.
    Stock GM hei wires are about 13-14K per foot.
    Accell racing wires are around  15K per foot. All brand new, never
    used.  FWIW.
    
    -john

    John,	Every article I have ever read about spark plug wire 
    		resistance has stated a norm of 4000 ohms per foot.
    		That is why I said what I said. 
    		In my opinion, why have high resistance it defetes the 
    		high output of the coil. I could be wrong.
    		Also why is ACCELL offering a racing spark plug wire 
    		that is under 400 ohms per foot? I was under the impression
    		that less resistance is what you want for a "hotter"
    		spark. Also why run a high out put coil?
    
    						jack    

    
        Higher resistance wires cause a hotter spark at a higher voltage
    at the plug. The coil will saturate longer to overcome the added
    resistance of the wires. The only drawback is that the wires themselves
    have to be made better and more expensive to avoid "flashover" and
    arcing to ground someplace in the path.
    
        Joe and sally average seem to have difficulty understanding that
    having a 80KV coil does not mean that the plugs fire at that voltage.
    Plugs in a normal engine in good condition, typically fire at around
    18KV.  The added benifit of a HEI system only comes into play when
    the plugs are old or covered with an oily film. Then the quicker rise
    time of the electronic ignition can overcome the high-voltage path to
    ground caused by a plug in bad shape. The older low voltage systems
    simply cannot do it. High resistance wires simply allow the engine
    to fire todays extremly lean mixtures. And with the benifit of carbon
    wire cores, you can listen to your stereo.
    
    -john

Resistance wires are used when you want to listen to your radio.

Carbon filament wires normally have a resistive value of 4-10K Ohms per 
foot.

Spiral wound carbon core wires (pioneered by Sorensen in the sixties) have 
a resistive value of between 400 and 900 Ohms per foot.  A fine wire is 
wound around the carbon filament, thus concentrating the RFI inside the core 
while providing a much better path for the charge to follow.  Most high 
performance, low resistance wires are of this design.

Solid core wire usually measures less than 0.5 Ohms per foot and is the 
optimal method of transferring energy from the cap to the plug.  With a 
solid core wire, however, you can't listen to your radio while the engine 
is running w/o hearing each and every spark plug fire.

Most computer controlled engines will exhibit unpredictable behavior if a 
solid core spark plug wire is used instead of a resistance wire.

    
        Who still has solid core wire? Or who even has spools available
    to make your own sets. I noticed over the past 10 years that even
    mororcycles have gone to carbon core or spiral because of increased
    electronic controls. You won't even find solid core wires on a
    lawn-mower. Maybe in a real world test, there is no performance need
    for solid wires anymore.
    
    -john

    
        Well I performed a test to figure all this out and here is what I
    came up with.
    
    10 mm racing wires (very expensive)
    The 12 inch long coil wire measured exactly 2.6K ohms.
    The longest wire, 40 inches, measured 8.6K ohms.
    
        I checked the calibration of my Fluke against some precision 1%
    resistors I had in a component kit.
    
    O.K. so what? Now I used a Johnson Outboard as a test mule simply
    because its the only thing that can use really short wires because the
    coils are mounted on the power-head and all the wires are only 8 inches
    long for every cylinder. I have this neato ignition KV tester that has
    a inductive pickup that sits on top of the sparkplug and the wire sits
    on that. Anyway, the shortest wire with the least resistance fires the
    plug at only 9.6KV, going to the long 40 inch wire had the plug firing
    at 18.9KV.  What does this prove? Who the hell knows! But I do know
    that higher coil currents create higher heat. I tested one more wire
    that was around 20 inches and the meter showed it fired at around 13KV.
    The experiment was good enough to prove that the laws of physics has
    not changed...and neither has Ohms law.
    
    -john

So what does your test say about the current present at the plug gap?

The lowest voltage has the highest current.  i.e. it'll perform better 
under load.

FWIW, I forgot the brand name, but I (just two weeks ago) installed a set of 
solid copper core wires on a blown 351 Cleveland motor for my friend in 
Australia.  He picked up the set of wires at the street rod nationals in 
Columbus last summer from one of the vendors.  They were brand new, current 
manufacture, might have been Holley.

    
         Yes...solid core wires regardless of longest one in the set or
    shortest will fire at the same voltage. I have done the test before
    on engines that had solid wires.  But Skip, regardless of how much
    current IS present at the plug, I think todays ignition systems can
    handle high resistance wires and the relativly low compression and lean
    mixtures.
         I had the #5 wire go bad on my truck about a year ago, and because
    I'm a cheap sob, I just bought that one wire from a AC Delco
    distributor here in town. After replacing the wire, it showed open on
    the ohmmeter. So I cut off the ends and shoved the meter leads into the
    core of the wire itself, still open! That wire musta been like a
    high-voltage conduit. The only time the engine ran bad was at full
    throttle under load up a fairly steep hill.
    
    -john

    
       Something I forgot to mention....I like solid core wires too; on
    vehicles that never get driven with licence plates on them.
    Solid core wires pose a sometimes hard to diagnose problem on very high
    output secondary systems. "crosstalk" Engines that fire the 5-7
    cylinders in sequence and have the two wires running side-by-side right
    down to the plugs-can actually induce enough current in the adjacent
    wire to fire the wrong cylinder. A simple seperation of the wires by 2
    full inches solves the problem, but I have seen lots of motorheads
    agonize over this problem before finding out whats wrong. Carbon-core,
    or spiral wound wires do not have the problem.
    
    -john

    I suspect (from some background reading on spark "wireless"
    transmitters from the turn of the century) that things are a lot more
    complicated than they seem..
    
    The design of the windings and the magnetic circuit in the ignition
    coil have probably changed to match the characteristics that the coil
    sees when firing through a resistance wire; the extremely low
    resistance of the spark seen through a low-resistance wire may in fact
    cause a modern coil to deliver less energy to the plug.. of course,
    it's not clear that energy at the plug is what actually fires the
    mixture, either..
    
    The load resistance will also change the damping of the spark waveform,
    and that may be a big part of the problems that show up with solid-core
    wires and computer controls.. not only is there more RF floating around
    under the hood, but also the current waveforms seen back at the
    ignition driver stage can cause ground bounce..
    
    Luckily, I don't *know* anything about this.. back to debugging DSP
    code..
    
    ...tom