One of the Worst Selling Points, New Vehicles

[Kestas]

I've too have seen these platinum pucks disappear some time before 50K.

I wonder - if a car specifies platinum, do I have to use platinum or can I go with copper plugs, as did Patman?

 

[Winston]

The electrode wear from "melting" and "splashing" as well as from impact of Cations on the electrode. A material with a high melting point will reduce electrode wear.

The wear will happen on the ground electrode or the center electrode depending on the polarity of the spark. If you have one coil per plug, all of the wear will happen on the center electrode. If you have a "waste spark" ignition system, half of the plugs will wear the center electrode, and half will wear the ground electrode. Here are some pics of spark plugs from my last plug change. I have a "waste spark" system, so half of the plugs had the ground electrode chunk of platinum missing.

Here is a photo of what 3 of the plugs looked like (60k miles). Note that the platinum chunk on the ground electrode is still there.

Here is a pic of what the other three looked like. Note that the ground electrode is completely gone, and some of the base metal has started to erode also.

 

[Chispas]

Winston, if you would, any additional comments

greatly appreciated !

 

[Winston]

quote:

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Originally posted by Chispas:
Winston, if you would, any additional comments

greatly appreciated !

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I have fooled someone into believing I know what I am talking about. Here is the excerpt from where I got my spark pluge wear info.

quote:

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(1) SPARKING WEAR
An electrode suffers wear whenever there is a discharge. The discharge caused by the ignition system in internal combustion engines is generally a combined discharge. It can be separated into the discharge resulting from the Capacitive component in the sparking circuit system, and the discharge resulting from the Inductive component. A Capacitive discharge is an electric discharge deposited in floating capacitive component formed in the space of ignition coil spiral, and between plug cable and engine. It has a very high energy density, and is characterized by high current flowing for a short time. This causes local temperatures of some
thousands of degrees on the electrode, and wear because of melting and splashing. On the other hand, in Inductive discharge, which occurs after the capacitive discharge, an electromagnetic energy deposited in secondary spiral of ignition coil is released. As the cations in the gas collide with the negative electrode(center electrode), with high kinetic energy, they throw out the atom on the surface of negative electrode. Although the current of inductive
discharge is as small as few mA, they are kept for several mSEC which enlarges the wearing.
(The mechanism of sparking wear is shown in Figure 5.) Therefore, use of a material with a high melting point is required to improve the sparking wear resistance.

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This is from a paper that describes the development of Iridium spark plugs.