Suzuki GSX-R 600 K4 Iridium Spark Plugs - Page 2

 

http://www.densoiridium.com/faq.php

"Q. What makes Iridium better?

A. Until recently, platinum was considered the best material to use on
the top of an electrode because of its durability. However, Iridium is
6 times harder, 8 times stronger, and has a melting point 1200 degrees
higher than platinum. Put that into a harsh environment such as an
engine piston chamber, and you have a spark plug that can resist wear
much better than platinum. Additionally, the DENSO Iridium Power alloy
is so durable; it allowed our engineers to produce the world's
smallest center electrode (.4mm) which reduces the voltage
requirements, concentrating its sparking power. Also, its smaller
size, combined with the tapered U-Groove ground electrode, allows more
room for the flame kernel to develop and produce a more efficient
combustion."

http://www.theodoregray.com/PeriodicTable/Elements/SparkPlugs/index.html
Elements in spark plugs

http://en.wikipedia.org/wiki/Spark_plug

"At one time it was common to remove the spark plugs, clean deposits
off the ends either manually or with specialized sandblasting
equipment and file the end of the electrode to restore the sharp
edges, but this practice has become less frequent as spark plugs are
now merely replaced, at much longer intervals. The development of
precious metal high temperature electrodes (using metals such as
yttrium, iridium, platinum, tungsten, or palladium, as well as the
relatively prosaic silver or gold) allows the use of a smaller center
wire, which has sharper edges but will not melt or corrode away. The
smaller electrode also absorbs less heat from the spark and initial
flame energy. At one point, Firestone marketed plugs with polonium in
the tip, under the questionable theory that the radioactivity would
ionize the air in the gap, easing spark formation. (See external link
below)"

http://www.theodoregray.com/PeriodicTable/Elements/SparkPlugs/index.html
Elements in spark plug


I tried about two sets of Champion Gold Palladium plugs in the
mid-1970's. Their claim to fame was that they ran too hot to foul with
the rather low voltage available from the coils. The part$ guy who
touted them to me said that I shouldn't worry about the fact that the
center
electrode would actually *melt* into a round blob...


"The Witnesses proved, without error or flaw,
"That the sty was deserted when found:
"And the Judge kept explaining the state of the law
"In a soft under-current of sound.

"The indictment had never been clearly expressed,
"And it seemed that the Snark had begun,
"And had spoken three hours, before any one guessed
"What the pig was supposed to have done."---Lewis Carroll, "The
Hunting of the Snark"

 

On a spark plug, we've got nothing like two identical electrodes.

The center electrode is fairly long and how well it's connected
to the heat sink (cylinder head) is one of the factors that determines
the plug heat number.
The side electrode is short, relatively thick and thus well connected
to the heat sink. OTOH it is very exposed.


AFAIK, transport of metal between the plug electrodes is the
last thing we want to see.

If I may make a guess, I would say that the heat of combustion
totally dominates over any electrically caused heating.

--
Ole Holmblad - Göteborgs Prima MCK / MK Pionjär
TDM850 / TT600R  FL#44  OTC#489  UKRMSBC#08
SGFPTH#00   Remove hat to answer by mail

 OH- schreef:

I said *When*,   I talked about lab-conditions.
And yes. We could make a fortune if we invented one and marketed it
right: 'More power, longer lifetime. less fuel consumption, good for
the environment, girls love it'.  I'd fall for the last reason.


It is inside insulator material, but I know what you mean. BTW, an
electrical
insulator usually also is a good thermal insulator.


Yes, there is no formula to calculate which one is the hottest.


Correct. But we see it. If it wasn't the case you'd never have to
install new plugs.


No guess needed. It does.

Let me retry to write what I wanted to say:

Heat is movement of atoms. The hotter, the faster they
move, or- in solid material anyway- vibrate.
Many atoms on the surface of hot material will jump off of the
surface, but most will be pulled back onto the surface
because of the force that holds atoms together.
But some will escape (if temp is high enough).
Water already does that at room temperature. We
call that evaporation. But note that evaporation does
not mean that the metal must be in a liquid phase.

If there is a negative electrode close by (an
electric field), then there will escape more
atoms from the positive electrode, because
the negative electrode pulls on them.

So *at equal temperature(!)* a positive electrode
will loose more atoms over time than a negative
electrode.

I don't know wether center or side is the hottest,
but the fact that usually the center is cladded with
expensive material makes me think that the center
is the hottest, or that the electric field helps the
center to loose atoms most, or maybe both things
together is the reason for center cladding.

Rob.