If anyone is looking into buying these very expensive spark plugs go directly to their site:
http://www.denso.co.jp/PLUG/iridium-e/index.html
These spark plugs sell for about $13.00 each, $68.00 for a set of four, and $99.00 for a set of six.
Now, is the power gain worth the money. I guess if you have the money then it's OK.

 

My spark plugs work just fine. If your current spark plugs work OK, why bother spending 13x as much on them. Just like w/ ignition boxes, this will only help if you are running seriously out of tune and misfiring due to the off mixture.
...ed

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Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Well I'mm gonna disagree with ED on this one,
I drive karts and use the new Rotax-max engines. These Denso Iridium power plugs come with the motor from the factory and are the only plugs that work well and let's you rev-it up to 14,000 rpm's. even in brand new motors those other plugs can't cut it. NGK and Bosch make a plug that's compatible but those are almost as expensive...

So they are not for out of tune engines but also for the utmost extreme engine needing the very best...

 

My LS1 has Denso's from factory. They seem like an okay plug but i don't know what the big deal is honestly...unless it's a Sam's Choice Spark plug shouldn't it work the same?

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR

 

the reason that these are the only plugs that will work is that the hardness of iridium allows denso to make the center electrode much smaller in diameter compared to platinum finewire or copper core plugs (.4mm vs .8+mm). a plug with a thinner center electrode requires less voltage to create a spark across the gap. so what i think happens is that at high RPMs, the coil(s) on the rotax engine can't recharge fast enough if used with non-iridium plugs due to the higher required voltage and so you get misfires. unless your car turns 6500+ rpm then upgrading any ignition components beyond OE is unnecessary. you can use platinum plugs for longer life, though.

 

i use pure iridium at work, it is by far the softest metal i've ever worked with, other than liquid mercurey. how is it or how does it's "hardness" enhance the electrode of the plug? is it an iridium alloy? just about have to be i'd guess to add hardness to the electrode.

 

it must be an alloy then because it would wear out too fast at only .4mm diam., or maybe it has some other property to keep it from wearing but you'll never see a platinum or nickel tip that small. the iridium electrode design we use at autolite is an alloy, i better not say what the other metals are, just in case it's proprietary info lol

 

what i have at work looks like bar solder and you can easily remove it with a finger nail. it has 99.9% pure cast into the bar.