NGK Iridium IX Spark Plug - TR6xi

Race Red Boss

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I'm going to inspect the plugs on my 08 Shelby. It's running well, and is a low mile car, but have read that the plugs should be replaced fairly frequently as insurance?

I suspect the plugs will be the NGK's.....which version, I'm not sure. My car has a 2.6 pulley and tune, so looking at the TR6xi's which I believe would be good for my boost level (11-12 PSI - according to stock guage).

Anyone else running these plugs and have good experience with them?
 

Catmonkey

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The IX is an iridium plug. Most guys run the TR7IX for higher boost, myself included, just because there's not much in the way of a colder plug. But if you change your plug frequently, iridium is sort of a waste. If you can get by with a hotter plug and intend to change them often, just use the TR6.
 

Race Red Boss

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^^^ Thanks Cat. Looks like Ford makes a plug that's one step cooler as well....SP471. The TR7xi might be overkill given my boost level?
 

PM-Performance

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The IX is an iridium plug. Most guys run the TR7IX for higher boost, myself included, just because there's not much in the way of a colder plug. But if you change your plug frequently, iridium is sort of a waste. If you can get by with a hotter plug and intend to change them often, just use the TR6.


I thought alot of guys move to the iridiums due to cleaner idle and less hiccups? I usually ran basic copper plugs colder in all my other cars, but I been sticking with the TR7IX due to that.
 

Catmonkey

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Iridium is used by the OEM because it can warranty the plug for emissions for 50k miles. The stock plugs were iridium. It's an exotic metal and is not a better conductor than copper. However, the only colder plug NGK has is a BR7EF with a copper core and it does not have a projected tip. I have a set I'll be trying at some point. I'm thinking the non-projector tip is going to foul easier, but if you replace them regularly, it probably won't make much difference.
 

HKusp

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I am running BR7EF's. I have gotten them off RockAuto.com and they aren't expensive. These were recommended by my tuner and so far I like them. I have about 9-10K miles since switching to them.
 

Willie

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Heat Range 5: TR55ix Stock #7164
Heat Range 6: TR6ix Stock #3689
Heat Range 7: TR7ix Stock #3690
Heat Range 8: TR8ix Stock #3691

I've used 3691 for over 10 years. Currently 24# boost. Never a hiccup and unlike the 3689 which I used to change every 5k miles due to misfires, the 3691 have held true.
 

Robert M

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Kenne Bell recommends TR6 heat range and a .035 gap.....That is for their S/C's. It seems that they do quite a bit of in-house testing on "their" products and spec. accordingly......

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R
 

Race Red Boss

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Just a quick update. I pulled the passenger side plugs today. Confirmed they are the NGK TR6IX's. All of them looked good and the car runs great, so will go with them again.

Thanks again for the input guys.
 

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