I had to swap out the boot on my MSD coil wire to an HEI style connection. Once I crimped the new connector on and slid the boot up over it I did an OHM check and I got a reading of 59.6. I also had my meter set for an audible tone but never got one all though I got the mentioned 59.6 ohms of resistence. I am not real good at this electrical stuff so does this sound like I am OK? Should I have heard an audible tone like I would have with an open circuit or does a coil wire not worki like that?

Thanks for any info you can give me.

Wade

 

Good MSD wires run about 50 ohms per foot... sounds like your good to go.

 

Most meters will not give a beep if the resistance is over 50 ohms, or my Fluke will not anyway.

 

Awesome thanks guys!

Wade

 

The Beep Tone is for continuity, very low resistance, so Eddie is right

 

You do not want a low resistance spiral wound wire, if it is it just means there's less fine wire than in a set that has a higher resistance. The whole low resistance hype is a marketing gimmick that leads customers into falsely believing the low resistance wires are better

 

I bought the 8.5 MSD's that are recommended for my setup. What would be wrong with these?

Thanks guys for the info on the tone and resistence reading. I learn something everyday. With electrical I have a lot to learn.

Wade

 

this may be obvious, but my multimeter has a "mute" button you have to press before it makes a tone. hopefully you would have noticed this already...

 

Thanks I did make sure that I could get an audible tone from a scrap peice of wire before trying on the coil. Trust me when it comes to me and wiring nothing is obvious. Thanks for the reply.

Wade

 

Think of it like this....the lower the resistance the more voltage you get at the plug. Solid copper core (Packard) will deliver the spark but your radio will static.....MSDs are fine.

 

The resistance of the spark plug gap is huge, so whether you measure 50 or 100 ohms its not something to worry about.

 

Makes plenty of sense to me. E=IR; voltage across the plug will be proportional to its resistance. Very little voltage will be dropped on the wires.

 

That's what they aim at for you to think and buy the low resistance wires. street wires are not solid core, oem is usually a cheap carbon conductor wire (assosiated with higher resistance levels) and aftermarket a spiral wound wire.

The way they measure resistance is by sending a 1 volt direct current through the wire, now an ignition system with it's coil acting like a pulse type transformer has AC characteristics, DC current travels through the entire length of a wire (like water through a tube) where AC travels through an induced magnetic field surrounding the outer surface of the wire. Because the resistance measurement is DC based it's of no use. For AC it's called impedance not resistance.

Now if we look at this, the spiral wound wires (which are spiral wound for RFI and EMI suppresion) with the least amount of fine wire (the shortest pieces so the least tighly wound) will show up as the lowest resistance wires in the test, this doesn't mean they are the best wire, they are not, they are just the wire with the shortest strands and thefore also cheaper to produce. The finest wound wires have the most surface and therefore are better at carrying an AC current than 1 thick wire (because the bundle of fine wire has more surface area).

Because with the tighter winding you add wire length this also adds DC measured resistance, this is marketing at it's best. Winding the wire much less tightly saves on cost (wire used) and it gives a lower DC resistance measurement. It's a win win situation for them selling a misrepresented product.

V (or E -> elctro potential)=IR ...yes DC!

For AC Ohm's law reads E=IZ where Z is impedance = squareroot(R^2+(2pi*f*L)^2)
where
R = resistance in Ohms (DC resistance)
pi = 3.416.....
f = frequenzy (hertz -> rpm signal/2 for a plug wire) [EDIT for typo]
L = inductance (henry)

 

 

TT:

That's quite a bit of info.

f = frequenzy (hertz -> rpm signal/8 for a plug wire)
Did you mean: f = frequenzy (hertz -> rpm signal/2 for a plug wire)
ex: 4000 rpms would yield a freq of 2000Hz, single plug wire only fires once on every other revolution.

Impedance is not always used for AC circuts. It is more common in situations such as RF, where it has a measurable affect. In household wiring, which is 60Hz AC, impedance is of little value. That does not mean that the local power company is immune from impedance.

 

yes /2 I dunno why I typed 8 typo ..sorry

When you apply Ohms law to an AC circuit you must consider the resistance of the circuit and the inductive reactance which together is known as impedance. Note where it says circuit and not "length of wire".

With the impedance I wanted to make clear that DC resistance and AC impedance (of a circuit) is not the same.

The spark plug wires, a spiral wound is not comparable to household wiring. As it is wound it has the characteristics of a coil, so basically it's a simple circuit. That's why this whole deal doesn't apply to solid core race wires which are not spiral wound

 

as TwinTurbo said:
"The spark plug wires, a spiral wound is not comparable to household wiring. As it is wound it has the characteristics of a coil, so basically it's a simple circuit. That's why this whole deal doesn't apply to solid core race wires which are not spiral wound"

Like in my previous post.

 

Does anyone know what the inductance of the coiled spark wires are. The resistance across a .050" gap is fairly significant. I doubt than anyone is saying to use 14/2 household wire. For someone like myself, who dealt in frequencies in the 54MHz range and higher range, a mere 60Hz looks like DC and was treated as such.

 

54mhz....a com system or radio? I do DC thru microwave...(22ghz+@100kw longpulse) and also laser/ir systems.
Larry

 

The frequency used for any of these calculations is not engine speed but the rise time of the spark voltage.