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Discussion Starter #1 (Edited)
i just ordered some goodies from Dan Newman for the Cougar.....among them, spark plugs....i figure since i have new Motorcrafts, new NGKs, and Bosch's with less than 5k on them, i thought i'd check the actual resistances of each plug to see the differences

Bosch: average 3.7 Kohms

Motorcrafts 22C: average 13.4 Kohms

NGKs TR6: average 3.5 Kohms

i was like...what the hell....my multi meter must be off....how can the platinums, which are supposed to have higher resistance, have less resistance than the 22Cs? could them being used a couple thousand miles have an effect on the resistance readings?

i'm gonna go to autozone to buy a couple brand new Bosch plugs (and return them back) just to i can satisfy my own curiosity....i'll edit this post when i get the new ones metered
 

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Discussion Starter #2
ok i got a couple new Bosch platinums to get a resistance reading.....this time using a multimeter that hadn't been dropped like one million times like mine

Bosch Platinums: average 2.6 kOhms, new

NGK TR6: average 4.05 kOhms, new

Motorcraft 22C: average 13.1 k Ohms new

so whats the deal guys? A-Train? Bueller?...... doesn't this go against what everyone always says about the copper electrode plugs being better conductor than platinum electrode plugs?

i'm curious to what everyone has to say
 

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Fry Rice Specialist
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this suppose to open a whole new world to us.....anyone?
i'm also curious....
 

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You are checking the resitence of a resitor plug the higher the reading the better the rf noise suppression. Correct in thinking but wrong application. What is the resitence of say .057 plug gap across air? Check the reading on something good like from the battery neg terminal to the engine block.
 

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Discussion Starter #5
aduty said:
You are checking the resitence of a resitor plug the higher the reading the better the rf noise suppression. Correct in thinking but wrong application. What is the resitence of say .057 plug gap across air? Check the reading on something good like from the battery neg terminal to the engine block.
thanks for your reply

is RF noise suppression really that big of a problem in spark plugs that motorcraft needs to purposely make their copper plugs with a high resistance (compared to platinum)?

i see what you are saying about the air gap.....and how it's gonna have a much larger resistance than any particular spark plug electrode

are the resistance values so low that they wouldn't make ANY difference, considering the resistance of the air gap?

i guess what i'm trying to get at is this: why does everyone say copper plugs are better for performance with the main attribute being that copper is a better conductor (which it is generally true) and thus serves as a better material for an electrode?
 

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I'm not an "electronics" guy, but it seems to me that what you are measuring is the resistance through the spark plug, from the connector at the top to the electrode tip. You're essentially measuring the 'wiring' inside the ceramic insulator that takes the current to the elctrode. Who knows what's going on in there??? Sounds to me like they purposely build resistance in there to supress the 'noise.' It may not even be copper conductor inside there, although I suspect is copper taking the current in and out of the resistor.

It seems to me that what goes on inside the ceramic doesn't mean a thing as long is there is sufficient power generated from the coilpack, so the votage drop through the resistance inside the ceramic insulator doesn't prevent there from being enough juice to jump the gap, and there is plenty of that to spare. What matters is how the juice travels through the electrode tip and how attractive the "target" on the other side of the gap is, and how easily the juice flows through it to ground.

That copper has a lower resistance value than platinum is fact and indisputable.

What you seem to have proven is that one manufacturer's spark plug's resistance from connector to electrode is significantly higher than another. While an interesting fact, in a normally operating coilpack, it should have no effect on spark at all. The higher resistance may or may not be overkill for noise suppression, but that may not be a bad thing ...
Disclaimer: It's only 6:00 a.m., I just woke up, and the only thing I know about electricity is that A = VR, so you "electron heads" out there feel free to flame me if I've got it wrong. It will teach me once again not to post beyond my experience.....
 

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Hmm it's plug time again I have several choices (keep in mind I have 98 F-150 heads- don't ask). Been looking at several choices Autolite 605/606 family(listed for use on Pontiac GTP's) seem to be the best I have found. Standard Copper resistor plugs.
Suggestions???Is there something better???
WTF I've got the whole weekend to play around with.
 

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Discussion Starter #8
96 GoldBird said:
I'm not an "electronics" guy, but it seems to me that what you are measuring is the resistance through the spark plug, from the connector at the top to the electrode tip.
isn't that where the current flows thru? from the top where the plug wires connect, down thru the plug to the tip of the center electrode? i mean, there is no other current path, obviously, or there would be no spark at the gap where it jumps to ground
 

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I'm not sure you read the rest of the post... what does the resistance in the ceramic insulator have to do with the spark? The resistance that affects the spark is the resistance of the material that carries the spark.. the elctrode and the receptor... How the juice gets to the electrode doesn't matter as long as there is enough to jump the gap. There is resistance purposely built into the path in the insulator and it has nothing to do with copper vs. platinum... a platinum plug does not have platinum throughout the plug, just at the tip.. that is where the spark is created and carried...

Platinum is put on the tip so the electrode lasts longer, period.. not for performance..
 

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Discussion Starter #10
i see.....that is a bit more in-depth and the type of response i was looking for......i'm real picky about that :) .....that does clear things up

before submitting this post, i just threw in the V-groove NGK TR6s and the 180* Tstat.....i checked (again just out of sheer curiosity) the resistance of the 32Cs that were in previously , and those averaged 3.4 kOhms....lol.....oh well....i'll just let them do their thing and move on....
 

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It doesn't matter which way the current travels, and in out stock ignition, the sides are opposite of each other.

You are measuring this with an ohm meter? The only correct way would be to measure the voltage and amperage when it fires. This is because the resistence if not nessessarily a stright line. DYK that when an unlit lightbulb has ~10 times the resistence it does that when it is lit? Same idea.
 

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I went ahead and measured a couple of plugs that I have. The first being a denso iridirum it 20 with about 15000 miles on it measured 4620 ohms or 4.62 Kilo oms.
The second plug is a motorcraft measured on 2 plugs was 3222 and 3500 ohms. The motorcraft plug is a awsfa12c
 

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Discussion Starter #13
GreenBird said:
It doesn't matter which way the current travels, and in out stock ignition, the sides are opposite of each other.

You are measuring this with an ohm meter? The only correct way would be to measure the voltage and amperage when it fires. This is because the resistence if not nessessarily a stright line. DYK that when an unlit lightbulb has ~10 times the resistence it does that when it is lit? Same idea.
yea i kinda knew the resistance readings might not be the entire story, as it turned out to be...it just seemed unlikely, but i had to ask :)

thanks guys
 

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Fry Rice Specialist
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the operating temperature might play a role too?
 

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chuacw said:
the operating temperature might play a role too?
yep. as a metal heats, the electrons become more excited, and that leads to lower resistence, but when it gets really hot too many become excited and resistence goes up (think traffic jam)
 

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I still don't see how the resistance inside the ceramic insulator leading to the tip (which is what has been measured) has anything to do with a comparison of Platinum TIPPED and Copper TIPPED spark plug performance..

Who cares how much resistance is in the ignition wires, and the wire leading to the electrode as long as there is sufficient voltage to jump the gap... The business is done between the electorde and the receptor, that is the resistance that affects the performance...

Resistor plugs have resistance built into them as to resistor ignition wires... none of that has anything to do with whether platinum TIPPED plugs outperform copper TIPPED spark plugs, or vice versa...
 

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Oh no... I remember being flamed over this topic a few months ago.

Good plug wires are just as important to ignition performance as the spark plugs. The wires must be able to carry the volts.

Copper spark plugs have a larger "copper" electrode diameter and platinum have smaller diameter "platinum" electrode. The diameter difference compensates for the electrical properties of the electrode. Humm... What about the surface area of the electrode?

Here is a link on Platinum Plugs
 

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Now measure the resistance of your plug wires and you will see why the resistance of the inside of the plug itself doesn't really matter.
 

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J.Miller said:
Oh no... I remember being flamed over this topic a few months ago.

Good plug wires are just as important to ignition performance as the spark plugs. The wires must be able to carry the volts.
I see we agree. I stated as much earlier, only slightly differently. The resistance in the wires/plugs is moot, if there is sufficient voltage from the coilpacks to withstand the voltage drop and still have sufficient power to jump the gap. The converse of that is as you stated, if the resistance is sufficient so as to drop the voltage, or impede the current to the point where the spark is effected, then obviously the resistance "matters." With a normally functioning coilpack and ignition wires any of the spark plugs presently on the market will not add sufficient resistance to adversely affect the spark.

Platinum plugs were not designed to improve performance and they don't. They were designed to be longer lasting, and they are.

And I can't imagine why anyone would flame you...... you are such a likeable guy :D
 
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