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Old 02-07-2013, 03:22 PM   #21 (permalink)
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Good luck with your new plugs! I'd like to know if you see a difference in MPG.


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Old 02-07-2013, 06:41 PM   #22 (permalink)
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Originally Posted by straight5 View Post
I'll stir this pot a little more lol
In my Saab,

Saab Direct Ignition - Wikipedia, the free encyclopedia

So yea, some of us have to use the recommended plugs.

I had the same experience on the Infiniti site. seemed the nkg were the only ones that didnt create problems.
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Old 02-07-2013, 07:41 PM   #23 (permalink)
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Pulled the plugs in the 97 Ranger. Looked like they had been in there since it was built, with 125k miles on them now, clean as new with a gap that was twice what it was originally. Put the same Ford plugs in, takes 8 for the 4 cylinder and the left side is a pain. The wires are original dated 1997. They still seem to be working fine. Plugs were iridium. Fortunately I still have my pin lock impact MAC extension and the 5/8ths swivel impact socket with the rubber boot that grabs the plug. I couldn;t get my hand within a foot of the number 3 intake side plug, totally installed by luck and feel.

factory plug wires are now 16 years old, when they start messing up, I'll spend the $65 for Ford wires, and replace them again when I am 80 years old, YEAH RIGHT!

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Old 02-08-2013, 12:45 PM   #24 (permalink)
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My '09 Corolla comes with iridium plugs OEM with a specific long reach specification. Each plug is located under a its own coil pack. All of this under an engine cover. The more one messes around un-attaching & re-attaching coil packs, moving & flexing plug wires etc. the more chances of failure. These components have to deal with heat and vibration so I don't need add excess flexing/handling to the mix. My Corolla's plugs are rated for 120,000 miles or 192,000 kms.

I have always used OEM specification for may cars. I have never had a plug failure or even a code showing misfire in any car I have owned.
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Old 04-20-2015, 10:47 PM   #25 (permalink)
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Originally Posted by Old Tele man View Post
...iridium is great for longivity, and the small "needle-point" electrode area enhances "arc/spark" creation.
To bump the thread and expand on this point a bit: the higher melting amd oxidation points of the iridium coating (and to a lesser extent platinum) allows a smaller diameter electrode - with copper, the extra heat from concentrating the spark like this would cause the electrode to erode.

The smaller diameter electrode has the desirable effect of concentrating the charge at the tip (see schoolphysics ::Welcome::). This increases the strength of the electric field at the electrode for the same electric potential (voltage), and just as with a lightning rod, this increased electric field strength causes the dielectric (in this case, air-fuel mixture) to break down at a lower electric potential.

AFAIK the main benefits of this for engine operation are
(1) More reliable timing - the spark is created at a lower voltage, so there's less uncertainty about what point in the voltage upswing the dielectric breaks down and the spark is formed.
(2) More stable spark - again, the higher electric field strength for a given voltage means the intensity and duration of the spark is more predictable.
(3) Potential for longer spark - the charge concentration effect also means in theory you could also use a longer spark gap and get the same electrical spark performance as a copper plug with a 'standard' gap - or trade off by using a slightly longer gap while still improving spark formation and stability slightly. Given the cost of 'precious metal' plus though (and the issues with re-gapping), I'm not particularly inclined to experiment with this aspect myself though .

One other advantage not related to the electric field is that the smaller area of the electrode means less heat is wicked away from the first bubble of burning fuel by the center electrode.

Bear in mind that even taken together, all these effects basically add up to slightly improved consistency of ignition timing, so the effects may not be huge. Also, other technologies like high energy ignition and coil-on-plug systems address similar issues. As with many things, there are real advantages, but YMMV
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Old 04-21-2015, 12:59 AM   #26 (permalink)
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Originally Posted by Blue Bomber View Post
Spark plugs are all about conducting electricity between a gap to ignite the air/fuel mixture. The better spark you get, the more complete burn you get, and the more power you get out of the fuel you're using (and less emissions, too). To get a better spark, you need to use a good conductor. Copper is one of the best conductors available for spark plugs, and is dirt cheap, though it has pretty short life span. Nickel and platinum aren't that great, and are only used by manufacturers because of their extended life span.

Iridium is the best of both worlds. Even though iridium itself isn't the best conductor, it's extremely hard. It'll last the longest of any spark plug tip material (some are rated up to 100K). Being so hard, the tip can be made to a fraction of the size of a normal one. This creates a very concetrated spark in comparison, which easily negates the lower conductivity of the metal. Iridiums are know to ignite lean mixtures that other plugs can't, which would definitely help fuel efficiency.

I had an 86 Celica GT-S, and it ran horribly on NGK coppers. Tossed in some Denso Iridiums, and it ran like a champ. Not sure what was wrong with the car, but it really liked iridiums. I'm running NGK Iridiums on my current MR2 Turbo, and it likes them just as well.
toyoto engines love lridium plugs as the engines are designed to run on them. My toyota 3vze engine has denso irdriums fitted as oem.
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Old 06-08-2015, 10:08 PM   #27 (permalink)
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NGK is a renowned brand, as far as i can remember. i was just looking around when i saw this thread. good read.
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Old 10-21-2015, 06:34 AM   #28 (permalink)
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Sorry to revive a dead thread but I purchased both the standard copper plugs and the Iridium plugs (both NGK brand) to test for a difference in mpg. So far, my scan gauge is telling me that I yielded a 4-10% increase in mpg with the copper plugs along my normal commute with no traffic, similar weather, and the same pulse and glide tactic. Further testing is required as I have not yet refilled the tank yet and can only go with what the scangauge is telling me. Will update this post in the coming weeks/months.

I drive a 2007 Toyota Yaris Hatchback by the way.

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