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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.

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.

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.

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.

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.

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)

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.

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.

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.

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.

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

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 indicated horsepower increases over stock plugs of 2-3 Hp in a naturally aspirated engine and 27 Hp in a supercharged/turbocharged engine as seen in the January 2003 issue of 5.0 Mustang & Super Fords magazine*.

*Copies of 5.0 magazine article and/or various applicable dynographs are available from DENSO upon request.

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.

Q. How do I gap Iridium plugs
A. Before attempting to gap any DENSO Iridium Power spark plug, please review the specification chart to see the factory-preset gap. In most cases your Iridium Power plugs do not need to be gapped. Even with small variations in the factory set gap the ultra-efficient firing power design will compensate for those small variations. Should you decide to re-gap your Iridium Power plug, use extreme caution as improper gapping may damage or destroy the Iridium center electrode or porcelain center. To increase the gap size: Step 1 Use needle nose pliers or spark plug gapping tool to bend the ground strap up to the desired height. DO NOT LET THE PLIERS OR GAPPING TOOL TOUCH THE IRIDIUM CENTER ELECTRODE OR PORCELAIN. Step 2 Re-check the gap with a calibrated gapping tool. To decrease the gap size: Step 1 Use the same method as above, however bend the ground strap down to the desired height. DO NOT LET THE PLIERS OR GAPPING TOOL TOUCH THE IRIDIUM CENTER ELECTRODE OR PORCELAIN. Step 2 Re-check the gap with a calibrated gapping tool. WARNING: Failure to follow these directions may permanently damage the spark plug. Note: Never use a round gapping tool to check the gap or to increase or decrease the gap setting.

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