Plug wire info needed!!!!!!

[99 R/T 10]

I am looking to switch out some spark plugs in the next couple of days, and thought I would do a resistance check on the MSD wires I have. They only have 5000 miles on them, but I want to check them to make sure they are still good. I have one of those ohms checker gizmos thingys(technical term ), but forgot what is considered good and bad. I know less is better(easier flow is always better, right?). So, looking at the thing it has 20K, 200K etc, which setting should I use and at what point should I replace them?

 

[99 R/T 10]

bump

 

[Joseph Dell]

I have no idea, but I can tell you that with the MOPAR performance wires, I can't get a good TACH signal when at the dyno... I need to borrown someone else's wire (just one) for the dyno run. i have no idea why that is, but it is the case.

JD

 

[J DAWG]

I need to learn what is the correct way to use one of those electrical checker thingies. I have one sitting in a box and I want to check my terminal ends at the pcm to make sure my harnasses are good or at least the wires in them.


Let me know if you figure it out.

 

[Gerald]

Rich, stick one end on your battery positive terminal. Insert the other end in your mouth. If your head looks like a marshmellow your wires are still good...


You going to Brandenton?

G

 

[joe117]

Put the meter in "OHMS" position.
If the meter has some other sockets to plug the leads into, make sure you have them plugged into the ones for ohms.
Set the range switch to 20k.
The meter will read out the ohms.

If it shows on "over range" then go up to the next higher scale.

When reading high resistance components like carbon plug wires, make sure you don't touch the metal ends of the probes with your fingers.
It might create an alternate path and screw up the measurement.

 

[KenH]

If you are using the MSD 8.5mm, they are rated at 40-50 ohms per foot, so you should measure around 50 to 200 ohms or so per cable depending on cable length.

 

[Steve-Indy]

Found a fouled plug on 99 ACR last year...checked original wire to that plug and resistance was 2000 ohms while similar length plug wire to "normal" plug was 500 ohms with about 8000 miles on car. New Mopar performance wires of equal length tested at 200 ohms.

 

[Chuck 98 RT/10]

I think there is more to it than just the resistance. I just change the wires when I change the plugs.

 

[99 R/T 10]

Rich, stick one end on your battery positive terminal. Insert the other end in your mouth. If your head looks like a marshmellow your wires are still good...


You going to Brandenton?

G

Who's rich? LOL, Thanks G, and yes, we'll see you there.

Mike

 

[99 R/T 10]

Ok, so I checked a set of Mangnacores I have and they won't read unless the gauge is put in the 20K Ohm setting, then it's like 5.3-4.9. I checked the wires on my car (MSD's) and put in the 2000 Ohms setting the read 90-150. Now the way I see it, the less the resistance the better, correct? I don't understand how a fairly new set of Magnacores can read so high and a used set of MSD's read so low. Am I off or are the MSD'a that good?

 

[KenH]

Ok, so I checked a set of Mangnacores I have and they won't read unless the gauge is put in the 20K Ohm setting, then it's like 5.3-4.9. I checked the wires on my car (MSD's) and put in the 2000 Ohms setting the read 90-150. Now the way I see it, the less the resistance the better, correct? I don't understand how a fairly new set of Magnacores can read so high and a used set of MSD's read so low. Am I off or are the MSD'a that good?

MSD wires are lower resistance then the Magnecors. What you measured on the Magnecors sounds about right from when I measured mine.

Measured resistance is not a direct corrolation to the performance of the wire or racers would just use regular copper wire with thick insulation for plug wires and have 0 ohms resistance.

Low resistance wires like the MSD are more likely to cause radio interference. I personally run the 10mm Magnecors.

 

[99 R/T 10]

But doesn't the higher resistance cause a weaker spark? Subsequently have unburned gas(less power)?

 

[BruceW]

Not really (unless your resistance is huge). The coils are putting out big voltages at low currents so the voltage drop across the wires is pretty insignificant.

 

[99 R/T 10]

Not really (unless your resistance is huge). The coils are putting out big voltages at low currents so the voltage drop across the wires is pretty insignificant.

So define huge. I mean, the MSD's had a resistance so small compared to the Magnacore wire. Isn't 5.28 (on the 20K ohm setting) a bunch for wires?

 

[BruceW]

Even at 1 amp of current (way more than the coil produces) your voltage drop difference between the two types of wires is about 100 volts. I'm not exactly sure of the numbers but your coils are putting out voltages of at least 10,000 V or more. You would have to have wires with resistances on the order of 1,000 ohms or more before you'd notice a difference. I would think the capacitance and inductance of the wires are more important than trying to compare the difference between 5 ohms and 100 ohms. Also remember that your DVM is reading static resistance (i.e DC), when you start talking about dynamic, high voltages things get really weird. Measuring the resistance in the wires is a good way to see if they are okay but not a good way to compare brands for their performance capability.

 

[Joseph Dell]

So can one of y'all explain to me why the mopar pefromance wires that I use (the blue ones) don't allow a dynojet to get a good tach signal? If I replace one of the wires with a stock wire, I can get the tach signal, but w/o that wire, no dyno operator can get a tach reading...

I'd love to understand this, but i'm still confused.

JD

 

[1TONY1]

So can one of y'all explain to me why the mopar pefromance wires that I use (the blue ones) don't allow a dynojet to get a good tach signal? If I replace one of the wires with a stock wire, I can get the tach signal, but w/o that wire, no dyno operator can get a tach reading...

I'd love to understand this, but i'm still confused.

JD

You can also use one of the signal wires going to a coil to pick up the rpm. I forget if the dyno operator uses the same inductive pickup or not. You could pick this up near the pcm or in the harness at the rear of the drivers valve cover.

Or, Most dynos have an optical pickup. They put a piece of reflective tape on the harmonic balancer and (usually) magnetically place the optical sensor near it. Unless you have good access to the balancer from the top, you need to raise the car to do this. Optical is the normal way they pick up rpm on diesels.