Purplexed

I copied this from a Mercedes Benz club site that I belong to.
Just a little FYI stuffSubject: [MB] Info on Iridium Spark Plug by Denso

Some info on the new Denso Iridium Spark plug.
Q. Where does Iridium come from?
A. Fifty million years ago, an asteroid composed almost entirely of the
precious metal Iridium (Ir-77) struck the earth, creating the Gulf of
Mexico. The resulting dust cloud destroyed most living things and ended the
dinosaurs reign on earth. Click here for more information.


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Q. Why was Iridium not used until today?
A. The extreme strength of the metal inhibited its large-scale usage in
spark plugs. However, through recent technological advances, DENSO has
harnessed the power of Iridium. DENSO’s patented alloy is composed of
iridium, complimented by rhodium (an even stronger metal). The rhodium is
added to increase oxidation and wear resistance. DENSO was able to make this
durable alloy workable by pioneering and patenting a Laser-Welding/process.
This process provides a 360-degree weld so reliable that the electrode
resists wear, even in the harshest conditions.


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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.


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Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in
automotive spark plug manufacturing, since platinum was introduced in the
early eighties. As vehicle manufacturers produce increasingly complex and
efficient automobiles, there is a greater need for long-life plugs that can
tolerate leaner fuel mixtures and improved combustion processes. DENSO has
responded to this need by developing its Iridium alloy, originally for OE
applications. For example, many newer Lexus’ and Toyota models carry an
ultra long-life Iridium plug variation (.7mm with platinum tipped ground)
that is capable of up to 120,000 miles of service. DENSO Iridium Power
plugs, with their .4mm center electrode, have been developed for performance
applications. Because gradual wear will “round-off” firing points over time,
the concentrated firing power and voltage requirement benefits will be
reduced. For this reason, DENSO advises replacement after 30,000 miles.


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Q. Why is the U-Groove special?
A. The patented U-Groove allows the flame kernel to fill the gap formed by
the U. This ball of fire develops a larger and hotter flash front a complete
combustion. The flat ground electrode design of ordinary spark plugs crush
the spark, inhibiting its growth; this effect is known as a “quenching
effect.” The simple, but efficient, U-Groove feature results in better fuel
efficiency, improved throttle response, and greater firing energy.


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Q. Do I need to set the gap?
A. Generally, no. The DENSO Iridium Power plug comes pre-set with a
protective sleeve over the firing end, to protect the gap from accidental
alteration. DENSO Iridium Power’s ultra-efficient firing power compensates
for normally recommended gap settings that are smaller than the pre-set
value. In the cases of vehicle modifications (nitrous, turbo-chargers,
super-chargers, high power ignition systems, etc.), some adjustments may be
desired. Or, if you prefer to remain consistent with factory specifications,
you may adjust. However, please be careful not to place any stress on the
fine center electrode during adjustment. You could accidentally break off
the very hard, and therefore brittle, tip.


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Q. Why are there different heat ranges? Which one should I use?
A. Part of your spark plug’s responsibilities, in addition to firing a
spark, is to remove heat from the combustion chamber. This is accomplished
by channeling the heat through the insulator material and metal housing.
From there, the heat is transferred to the cylinder head where the engine
cooling system can go to work. A spark plug’s heat range is its ability to
dissipate heat. The “colder” the plug, the more heat it can channel out of
the combustion chamber. In a performance application, colder heat ranges may
be necessary to handle the extreme temperatures brought on by higher
compression ratios, forced induction, and high RPM’s. While “Colder” plugs
may seem to be the way to go, please remember that the spark plug must
achieve its “self-cleaning” temperature where it can burn off fuel and
carbon deposits. Otherwise, the plug could “foul out” where it is prone to
misfiring and poor acceleration. A plug that is too “hot” can overheat, also
causing power loss, detonation, pre-ignition, and possible engine damage. A
good, general rule of thumb is to start with the factory recommended heat
range. For every 75 to 100 hp you add to your engine, you may go to the next
colder step. DENSO heat ranges move up as they get colder; 16 would be our
hottest Iridium Power plug, 34 would be our coldest (ranges;
16,20,22,24,27,31,34)


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Q. What vehicle applications are covered?
A. DENSO Iridium Power spark plugs were initially introduced for popular
import applications such as Toyota, Honda, Acura, Mitsubishi, and others.
However, since our product launch, we have added spark plugs that fit
popular “Big Three” makes such as General Motors, Ford, and Chrysler.
Currently, DENSO Iridium Power offers nearly full coverage for all passenger
cars, light trucks, and vans. Soon, we will be launching plugs that will fit
most motorcycle and powersports applications.


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Q. What kind of performance will I get from this plug?
A. Generally, you do not purchase spark plugs for performance enhancement.
While DENSO Iridium Power spark plugs have contributed to numerous
accomplishments through dyno-testing and actual use, their true benefit lies
in their efficiency, durability, and improved firing power. Serious tuners
modify their vehicles by increasing boost through turbo-chargers,
super-chargers, and Nitrous. They are also known to add high-energy ignition
systems, tinker with timing, adjust fuel mixture ratios, and increase
horsepower through other means. Putting these kinds of demands on their
engine increases the need for an efficient, durable spark plug that can
handle these kind of harsh environments. That’s where DENSO Iridium Power
can make a major difference.


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Q. What torque recommendations do you give for the Iridium plugs?
A. Improper installation may cause poor performance and could result in
costly engine damage. Click here for a table listing torque recommendations
for the DENSO Iridium Power spark plugs.


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Q. Where can I buy DENSO Iridium Power Spark Plugs?
A. Click here to find a dealer in your area.


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Q. What kind of testing has been done?
A. Iridium Power has been tested in many arenas. The most common area of
testing has been on the track. There are currently many people using the
plugs in import drag racing, with results being quite favorable. Some racers
have seen E.T.’s decrease by a tenth and less fuel consumption during a
pass. Circle track racers using the plugs notice better acceleration coming
out of corners and more consistent idling. The other area where the plugs
have been tested are on good old dynos. The results have fluctuated from 2-3
horsepower to 40 horsepower (all tests performed by independent companies
DENSO can not confirm or deny these claims). The differences in dyno results
are due to the complexity of the engine being tested. In general the plugs
have shown a 2-5% increase in efficiency of the engine.


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Q. I’m still not sure about DENSO Iridium Power Spark Plugs. I would like to
ask a question. Who can I talk to?
A. Click to Contact Us. Or, you can call our technical department or send
your question via our contact form. We will respond to your question
shortly.