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Discussion Starter #1
I'm about to replace the stock speced Denso platinum plugs on my '89 Supra NA. Any plug recommendations? Are the NGK or Denso iridiums worth the extra money? I'm satisfied with how well the stock speced Denso platinum plugs have performed over the years, so I'm leaning towards the Denso iridiums.

Comments and advice welcomed.
 

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Some people have recommended against the Iridiums, but they still perform well.

I'd probably stick with the platinums or maybe NGK G-Powers.

It wont make too much off a difference. If anything upgrade your stock plug wires.
 

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There are no gains to be had from ignition upgrades for quite a while up the mod chain. If there's no spark blow out, and you rely on the stock ECU to do the numbers, you're fine with the stock plats. Hell, even coppers are fine with a more frequent replacement schedule.
 

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Discussion Starter #4
Thanks guys. I really was just looking for longevity from the plugs as my Supra is totally stock NA and I'm not into changing plugs every 12,000 miles. Maybe the NGK Laser Platinum will be the best choice. I already have a new set of NGK premium wires to replace the originals. (Hope these aren't crappy wires.)

As an aside, I discovered that Denso actually makes at least three different Iridiums. Of course we are getting just their cheapest version presently, unless you buy the correct new Lexus or Toyota.

http://www.spark-plugs.co.uk/pages/technical/iridium_spark_plugs.htm

http://www.denso.co.jp/PLUG/index.html
 

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Platinums are bad and iridiums are overkill.

The NGK Coppers (3230s if I recall) are just fine, especially for a stock turbo motor, the gap will have to be different for an N/A Motor however.
 

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Discussion Starter #6
Jeeves said:
Platinums are bad and iridiums are overkill.

The NGK Coppers (3230s if I recall) are just fine, especially for a stock turbo motor, the gap will have to be different for an N/A Motor however.
First, this is a NA motor, not a turbo motor.

Further, why do you state that platinums are bad? Both sets original Denso platinums I've had it in worked flawlessly for 60K and 66K miles. Never a hint of detonation or missfires, always started easily. When pulled, they look like a poster child of the perfectly working spark plug.

And from researching spark plugs the last few days, I understand that not all platinum plugs are created equally. Various amounts of platinum are used and different locations, some with platinum just on the center electrode, some on both the center and ground electrode. A few with platinum on the center electrode and something exotic on the ground electrode.

Then there are the electrical and thermal conductivity characteristics of various metals used. Copper is a good thermal and electrical conductor, but poor on wear characteristics. Platinum have great wear chracteristics, but are not that good at electrical and thermal conductivity, however, it must be good enough since the previous platinum plugs worked well. Maybe in a highly boosted turbo or nitrous application the copper has an advantage because of heat issues, but I don't think a blanket statement that "platinum plugs are bad" is justified, IMHO.
 

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I say this because Platinum plugs are often the source of poor performance issues in 7M's. Bounce on over to supraforums and read all the rants about them.

I've had nothing but failures with them as well, switched to NGK Coppers and all my issues disappeared.
 

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Discussion Starter #8
Jeeves,

I did a quick search on supraforums and anyone who was having problems that I ran across was running a turbo. And who's not to say they didn't have other issues like a weak ignition system for whatever reason. Further, we probably only see posts on people who are having problems. How many people who run the turbos in stock form and the stock spec platinums aren't having problems and therefore don't post?

As I mentioned before, I've gone 126K miles (60K+66K) with the stock speced PQ16Rs and never had a spark plug issue. I don't doubt your issues with platinums, but if it we're me, I wouldn't make a blanket statement like that without some good documentation and related parameters to back it up. Just the same, thanks for your input.
 

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7M-GTE Coil packs are far from a "weak ignition system", there isn't a reason to even upgrade them unless you're passing the 500+hp mark.

As I stated, that's specifically what I know of the 7M-GTE. N/A's were never my boat. For us boosted punks, Platinums are the devil. Especially Bosch.
 

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Everyone here runs plats on the turbo. Bosch are hit and miss, the the 4 pole ones are just crap, but any properly functioning ignition system I've seen runs the Denso or NGK without problems. That said, the copper's are a better sparking plug by chemistry, though they have a shorter life.

Bob
 

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Interesting, I've never heard of a single positive plat. review down here in NM. Oh well.
 
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