Any reason to use those high dollar plug wires...

[amc fan]

Back in the day we used Packard 440 wire and Raja Bakelite spark plug connectors. You could see arcing at night with the hood open.

[stealth]

I may be wrong, but I'm always interested to see what the NASCAR boys are using..

I'm doubtful anyone does more dyno testing looking for a few hp....

[tenxal]

Testing wires on the dyno can be an eye opener.

Anything that you feel comfortable covering in more detail than that teaser?

Honestly, I haven't found any solid, repeatable correlation that points to price, diameter, resistance, etc. as a definite way to pick 'the best' wire. It's something you just have to test if you're on a dyno.

I do believe that several things we can't quantify/measure are in play....dynamic cylinder pressure and combustion chamber burn characteristics, for example.

[BradH]

Fair enough.

[Krooser]

I may be wrong, but I'm always interested to see what the NASCAR boys are using..

I'm doubtful anyone does more dyno testing looking for a few hp....

Scott wires are used on many Cup team engines.

I do like the Scott wires as they.will custom build length, ends, heat sleeves and even colors. You can run them over the covers, behind the heads, under the headers....anyway you want.

When Im ready Im going to mock up the engine in the car with my headers and make a decision.

[rebelyell]

Perhaps Cup's distributors (& carbs) have gone the way of the buggy whip. Multi coil-packs & appropriate hi-tension leads. Seems McLaren supplies ECU to both Cup & F1.

agree Scott sp wires very good; had em on conventional sbc CT car.

[rebelrouser]

Testing wires on the dyno can be an eye opener.

Anything that you feel comfortable covering in more detail than that teaser?

Honestly, I haven't found any solid, repeatable correlation that points to price, diameter, resistance, etc. as a definite way to pick 'the best' wire. It's something you just have to test if you're on a dyno.

I do believe that several things we can't quantify/measure are in play....dynamic cylinder pressure and combustion chamber burn characteristics, for example.

[rebelrouser]

Testing wires on the dyno can be an eye opener.

Anything that you feel comfortable covering in more detail than that teaser?

Honestly, I haven't found any solid, repeatable correlation that points to price, diameter, resistance, etc. as a definite way to pick 'the best' wire. It's something you just have to test if you're on a dyno.

I do believe that several things we can't quantify/measure are in play....dynamic cylinder pressure and combustion chamber burn characteristics, for example.

I am not smart enough to quantify it exactly, but I do know that you can watch an ignition scope pattern, look at the burn time section of the pattern and get a good handle on how much cylinder pressure, spark plug, gap, and even the mixture in the cylinder. I have done it for many years diagnosing engines. IN using a scope on performance ignition system, my main issue is a lack of good and bad waveforms for lets say a CD MSD ignition system. I have my own experience, but on OEM stuff there are large wave form libraries to look at and compare. But I have hooked up a scope made a movie of it during a pass and quite quickly figured out if it was a fuel or ignition miss fire for example. And I can tell if a cheap set of wires is a cheap set of wires.

https://www.motor.com/magazinepdfs/052001_04.pdf
https://wyzeprobe.wordpress.com/tag/lea ... n-pattern/

[Circlotron]

Simple physics will tell that the resistance of the air gap of the plug no less the addition of the very thick Atmosphere that gets created in the chamber at TDC is infinitely more massive then the resistance of even a pig cheap 20 ft long spark plug wire!

Stop wasting cash on low resistance wires and go for the wires with ok levels of resistance, but the best insulation!!!!

That resistance of the plug gap is certainly true, but only before the plug fires, before it has begun to do anything. Once it has started to arc, the voltage drop across the plug gap is about 1500 volts when you have 70 milliamps flowing. That translates to a bit over 21,000 ohms. With higher currents the plug voltage stays much the same so it is not a pure resistance as such though.

[rebelrouser]

Simple physics will tell that the resistance of the air gap of the plug no less the addition of the very thick Atmosphere that gets created in the chamber at TDC is infinitely more massive then the resistance of even a pig cheap 20 ft long spark plug wire!

Stop wasting cash on low resistance wires and go for the wires with ok levels of resistance, but the best insulation!!!!

That resistance of the plug gap is certainly true, but only before the plug fires, before it has begun to do anything. Once it has started to arc, the voltage drop across the plug gap is about 1500 volts when you have 70 milliamps flowing. That translates to a bit over 21,000 ohms. With higher currents the plug voltage stays much the same so it is not a pure resistance as such though.

The ignition energy has to ionize the air for the spark to jump the gap, the compression pressure, turbulence, and even amount of hydro carbons changes the voltage needed to do that. A cylinder with a rich mixture will have a different burn time than a lean cylinder. How many old hot rodders closed up the gap to stop miss fires after they installed a blower?
Have you ever used one of the old spark plug machines? You would clean the plug, install it in the machine, a coil fired the plug, and then you slowly add air pressure until the spark winked out. By this way it gave you reading on how good the plug was. All you have to do is run a gas fouled plug in one of those machines to see why a rich mixture causes a miss fire. The voltage will run over the carbon down the side of the plug, and never jump the gap.

[dannobee]

Stop wasting cash on low resistance wires and go for the wires with ok levels of resistance, but the best insulation!!!!

That's the truth right there. I was chatting with a Packard Wiring engineer and ended up getting an hour long lesson in spark plug wires. Turns out insulation (the white silicone between the conductor and the outside sheath) is where the money is. Silicone of that type is graded from 300 to 1400, with the higher number usually being used on very high dollar applications such as turbine engines and the like. But as a consumer, there's no way for us to quickly know the quality of any aftermarket wires. The OEM's, on the other hand, know exactly what they're buying because they're the ones who have to warranty their spark plug wires. So if you stick with OEM spark plug wires, of practically any brand, you're at least guaranteed that the factory trusted them enough to make it through the 50,000 mile emissions warranty.

[NewbVetteGuy]

You only need enough ignition energy to light the mixture in the cylinder, any more is overkill and can actually cause problems.

https://4.bp.blogspot.com/-OxA64QjYFiQ/ ... 0/fuel.bmp

Yes, but...

More voltage allows you to jump a bigger gap AND more voltage and a bigger gap helps you to light off leaner mixtures and higher pressures. (If / when a larger starting flame kernel results in less required ignition timing, that's "free torque"; not a significant amount, but something. From a fuel economy perspective to support really lean burn at cruise, useful...)

This is a REAL question: You need the big initial voltage to jump the gap and ionize the air, but as soon as the air is ionized the resistance at the gap drops to near zero (I've heard "negative resistance" across an ionized gap before, even), THEN if you're dealing with non-resistor plugs, the resistance of the wire IS the resistance limitation for any energy flowing across the ionized gap. (I'm not sure how much energy ends up transfering across the ionized gap after the initial spark jump and gap ionization.)

Isn't the resistance a much bigger deal when you're talking about CD ignition and much larger voltages vs. inductive ignition systems, too?



Context: A lot of these questions are coming from following a lot of the guys playing with simple DIY plasma ignition systems that combine an inductive coil with a CD coil and have the CD coil simply dump it's charge over the ionized air in the gap that was created by the inductive system firing immediately before. The size and intensity of the plasma they can create is VERY closely tied to the resistance from the coil and through the plug in these cases as the spark gap resistance is zero.

These guys just use a non-potted inductive coils, and add a capacitor connected to hte negative output to the primary coil's LV negative input and run a 2nd high voltage wire to the spark plug base; then put a diode string on the spark plug side of the small high voltage wire to stop the initial inductive voltage firing from running backwards up the small high voltage wire. (Inductive coil fires, voltage on the coil drops, causes cap to dump and CD to fire across it's parallel high voltage wire connection to the plug and a 2nd VERY HIGH voltage strike happens across the now ionized plug gap. With extremely low resistance the majority of the energy goes to producing plasma. -You get a long duration initial spark from the inductive oil and a very short duration, high voltage and high energy spark from the CD coil and sweet, sweet, plug eroding, large "kernel" plasma and reduced ignition timing requirements.


Adam

[Circlotron]

This is a REAL question: You need the big initial voltage to jump the gap and ionize the air, but as soon as the air is ionized the resistance at the gap drops to near zero (I've heard "negative resistance" across an ionized gap before, even),

Negative resistance doesn't imply less than zero ohms, it means that as the current through an electric arc increases, the voltage drop across the arc decreases somewhat instead of increasing proportionally to the current like in a normal resistance.

[tenxal]

FWIW (i.e., nothing), I settled on build-my-own MSD 8.5 mm Super Conductor wires w/ ceramic plug covers where there were issues w/ the plugs being too close to the headers for any other type of boot to survive the heat.

Brad, based on what we've seen on the dyno with quite a few engines....the Scott wires (my favorite) the MSD's you have or the FireCore 50's would be my choice.

A set of high dollar, big name, wires on my own engine on the dyno were just awful things......

[David Redszus]

OK we have figured out how to use a waxed string lead with a super coil and magna capacitor and can transmit all of 13% of available energy to the mixture. It does create a spark.

How long does the spark last? How many crank degrees of spark duration is adequate?