Electrical resistance/etc of Copper

Factual Questions
1

Hi,
I’m on the sparkplugs.com web page shopping for new sparkplugs for my car and I find that if I click on the hyperlinked word “Iridium” a javascript popup window will appear giving some stats on various metals.

As an owner of iridium plugs I thought nothing of it until it occured to me that until Iridium plugs, the preferred copper plug properties are not available for comparison. I understand this information is ordinarily quite accessible to any average Googling, but I’m not looking for the properties of copper wires. I’m looking for the properties of copper as it applies the other information in the chart provided by sparkplugs.com.

You can find a link to the Iridium pop-up windows by going here first: http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1191563

and the clicking on any of the hyperlinked “iridium” words in the “Product name” category. Can anyone “complete” the chart that Sparkplugs.com started?

2

QUESTION; Why is a copper plug preferred?

To the best of my knowledge, COPPER has never been used as a component of manufactured spark plugs.

Simply pick out whatever suits your fancy and drive happily down the road.

The use of exotic metals is to provide a better arc (spark) and justify a higher price.

NO, That information was not found.

3

Wanna bet?

4

Taking a wild ass guess that the car speced in your link is your car, I would just go with the OE NGK plugs for $2.44 each.
I very seriously doubt that you could measure the difference between them and and the $12. Denso plugs.*
But hey it’s your money, and your car. Knock yourself out.

*It is possible that your car will go 0-60 faster due to your much lighter wallet.

5

Like hell,
Copper is the most prevalent spark plug out there, it’s your standard plug that’s been around before Platinum, Silver or Iridium. Granted there is nickel in with it, but it’s not called a Nickel sparkplug it’s called a Copper sparkplug.

But really folks, I asked a fairly straight-forward question and all I get back is “this stuff” you guys are going on about. Last I checked GQ didn’t really cover personal opinions. If you’re not really interested in helping me with the question asked, don’t do me any favors by making up your own.

If I thought the Question was so unreasonable I would have never posted it; I just figured some of you Engineer types might easily reference most of the info in one of your little resistance manuals or what not. But it’s fine I found the melting point and I’m sure the other attributes can be collected one by one if I do enough digging…

6

Starting with the link you provided, I went to:

“COPPER core”
Indicates that the CORE of all(?) plugs are copper and it is only the electrode ends/tips are an exotic metal.

Copper electrodes would have a very short usefull life.

7

I went to link provided and then to:

S. P. Construction This indicates that all sp’s have copper cores.

It is the electrodes/tips that are made from exotic metals for endurance. Hence only those materials are listed in the table.

NO. They don’t make/sell “copper” spark plugs!

8

From the good fellows at Goodfellow:

Hardness (Vickers)
Cu: 49-87
Ir: 200-650

Electrical resistivity ( µOhmcm )
Cu: 1.69
Ir: 5.1

Melting point ©
Cu: 1083
Ir: 2410

Tensile strength ( MPa )
Cu: 224-314
Ir: 550-1200

But IMO, none of this means much in terms of spark plug performance, because:
[ul]
[li]Iridium is generally used in alloys, not as pure metals[/li][li]Electrical resistance of the electrode is negligible compared to the resistance of the wires and connectors[/li][li]The electrode is not a load-bearing structures and aren’t subjected to being scratched, so hardness and tensile strength are irrelevant[/li][li]None of these numbers tell you anything about resistance to corrosion[/li][/ul]

9

Thanks for the info scr4, I appreciate getting the info I was actually wanting.

[QUOTE=scr4]
From the good fellows at Goodfellow:

But IMO, none of this means much in terms of spark plug performance, because:
[li]Iridium is generally used in alloys, not as pure metals[/li][/QUOTE]
The sparkplugs.com website goes into this, however in this case it is a small bit of pure metal.

[QUOTE=scr4]
[li]Electrical resistance of the electrode is negligible compared to the resistance of the wires and connectors[/li][/QUOTE]
I’ve got this taken care of.

[QUOTE=scr4]
[li]The electrode is not a load-bearing structures and aren’t subjected to being scratched, so hardness and tensile strength are irrelevant[/li][/QUOTE]
That’s ok, just trying to “complete” the chart, thanks though.

I’m sure the sparkplug manufacturers have already looked into this before they decided to introduce the product; Denso/NGK make a pretty good product line. Good lookin out though. later