What Plug wires for MSD:accel vs Splitfire vs Mopr - Page 2 - Off-Road Forums & Discussion Groups
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post #11 of (permalink) Old 12-29-2002, 10:34 AM
Way Outta Control
 
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Re: What Plug wires for MSD:accel vs Splitfire vs

It's really interesting to look at all the "Hoop-la" about
plug wires. From expensive "magic" ones that make you think
you don't even need a coil to plain old junk ones.

The "potential" voltage or "power" is generated by the ignition's
coil and coil's control (module etc.)

The plugs are the things that determine how much voltage is
needed to fire the mixture. Changing coils or modules does
absolutely nothing to change the plug's voltage requirements.
Typically a plug needs about 8-10 KV at slower unloaded speeds,
and a maximum of about 18 KV at high loads.
Gap, compression, mixture, and position make that determination,
nothing external.

The "potential," or Available Voltage" that an ignition system
"can" put out typically is from 28-35 KV for stock systems,
and 30-40 KV for aftermarket. Claims of 60 kv, 80 kv, even
100 kv are just that - claims. Typically those don't even
measure up to stock ignitions - made to sell, not to use.
It's easy enough to check/prove/disprove it with any automotive
scope.

The difference between the "required" voltage needed and the
"available" voltage is called "Reserve Voltage."

That Reserve voltage is mainly in case the plug requirements
change, like the mixture goes waaaay too lean or the plug
fails or fouls, or the wire fails or starts stealing energy.

The main reason some ignitions work better than others is
the rise time of the voltage - how fast, or how hard it "hits"
the plug, blasting any crud off it.
And the duration of the spark - how long the spark stays jumping
across the electrodes igniting the mixture.
Like lighting a barbecue, the longer you hold a match to it
the better it starts a fire - within reason.

The wires simply carry the energy to the plugs, they do not
"generate" any "power" at all. (But reading some of the hype
sure looks like the wires do it all!) The best you can hope
for is that they carry ALL of the energy to the plug without
losing any of it through insulation breakdown or dissipating
any of it through internal resistance. And, of course you
don't want the ends to fall off from vibration.

Actually you could use bare copper wires if you could keep
the energy from jumping to ground. The trouble with solid
wires is they carry lots of radio frequency interference,
disrupting radio reception, and even interfereing with on-board
computers. Resistance added to the conductors helps to
supress these higher frequencies, but also limits the
amount of ignition current that can pass through the wires.
That becomes a trade-off.

The spiral wound conductors suppress the high frequencies
better, but still use resistance to help suppress them.
They are just "less worse."

Insulation that's heat resistant, like silicone, is better
than the plastic used on cheapies. It also has to be impervious
to oil and water soaking. Look for ALL parts of the plug
wires to be silicone, not just the wire insulatuion, but the
boots as well.
Lots of the cheapies advertise silicone, but only use it on
the boots, or only on the wire itself. Ya gotta look!

The internal conductors used range from carbon soaked string
to carbonized plastic. You don't want that conductor to break
or crack inside the insulation. Once there's a tiny crack,
the spark has to jump across the tiny gap formed. Every
time the spark jumps across it, it burns the broken ends,
making that gap wider. Eventually the spark can no longer
jump that far - then it misfires.

Obviously the ends have to be strong enough to hold onto the
terminals, and be securely fastened to the wire's core.
Ya gotta look!

Unfortunately there is no "magic" set of wires, none will
generate any more energy than what's there already - in
spite of some claims.

7mm vs 8mm --- just a silly millimeter more, but makes a
big difference in dielectric strength.

It's good practice to always use a dab of silicone dielectric
grease on both ends of plug wires. That's not the same grease
used on modules for heat sink.
It seals out moisture, and makes it much easier to remove
them next time without breaking them.
Also good practice to use a plug boot puller the pull the
boot off the plug, a little inexpensive tool that will save
your wires from breaking.
And, always twist the boots to loosen them before pulling on
them.

As always, you get what you pay for - to an extent, but a
high price really doesn't mean they are quality - just
expensive. (Old PT Barnum was right.)
Again, ya gotta look closely!
RRich is offline  
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post #12 of (permalink) Old 12-29-2002, 10:45 AM
Way Outta Control
 
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Re: What Plug wires for MSD:accel vs Splitfire vs

By the way - an interesting trick you can win a few beers
with.

Remove the coil wire - instead of the coil wire, plug in an
old dirty vacuum hose.
Start it up!

The black coloring in the hose is carbon, and the dirt is a
conductor too.
Just don't let it touch anything, the whole thing is the conductor
with no insulation.
Ever see an ignition spark jump to a vacuum hose or heater
hose? Same thing.

The resistance is too high to run well, but it should idle OK.


Ever take the "Mechanic's Test" ritual?
Standing on the front bumper and peeing on a plug while it's
running.




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