This isn't quite correct.
The heat range relates the sparkplug's ability to remove heat from itself in the cylinder. A 'colder' plug conducts more heat to the head to help cool the plug between firings so that it doesn't become an ignition scource, unfired. More boost, and leaner AF mixtures increase combustion temperatures and thus heat the plug more. A colder plug cools faster and thus is better for a higher performance application.

 

Good spark plug info here:

Click me

 

interesting note here, I've been looking for a local place for the copper NGK BKR7E plugs, but no auto parts stores (kragen, pep boys, autozone, all pro, etc...) seem to stock them. that plug is more commonly used in motorcycles like Kawasaki's and Yamaha's. The first local bike shop I called had plenty in stock.

 

As do we

Mike

 

turbo xs reccomends NGK PFR7G if you have a utec and want to replace your plugs. .. so what should i go with???

 

I think the OE NGKs are still avail from NGK....PFR6G. They also are OE for some Volvo applications.

The plug swap job is a little tedious. It's best to set aside a good couple of hours the first time you do it. I did my first plug change in about 1.5 hr, and ran into no problems. It gets tight down at the cam covers, you'll need a short extension and a good plug socket. Yes, be really careful installing the new plugs, start them by hand and get them snug by hand before you start racheting them in.

The colder plug will allow the plug to transfer heat away through the plug body (through to the cylinder head) more efficiently than a "hot" plug. The cold plug has less material at the center electrode shell exposed to combustion than the hot plug does.

What I wonder about, will the # 7 plug (one step colder in NGK), make the knock sensor less sensitive? Let me re-phrase that: will the colder plug cause less detonation, in turn less triggers to the knock sensor and the ECU will retard timing less frequently? In theory it makes sense, but has anybody tested the 7's in a bone-stock motor?

Thanks-
Jim

 

I'm going to try and log a run this weekend and compare to a run before I changed to the #7 plugs. if there's anything significant, like a bump in Advance Multiplier or knock correction, I'll post something about it.

 

Cool....please post what you find, I suspect Subaru dictates the 6 heat range for keepinfg the plug clean for long duration use and for environmental reasons, but maybe somewhat sacrificing all out performance when the car is driven in anger, as we all know what it feels like when you bog the motor and you get a little PING and then she runs like a wet dog. Try short shifting on a hill when you've got the AC on and you're done for. I'm hoping the colder plug will make the knock sensor less ticklish and convince it to calm down. Maybe Subaru engineered it to be safe when grandma loafs the car up hills at 1900rpm in 3rd gear in summer, but for those of us that know how to drive the car.....

Thanks
Jim R.

 

Any results ever come from this test?

 

How good are the Denso Iridium Spark Plugs compare to the NGKs? I am running a stage 2 with COBB Access Port ECU and I don't know if I should go with the; One Range Colder, or the Stock Heat Range in the spark plugs and if I should go with Denso or NGK. Any recommendations will be great.

 

I have NGK Coppers, one step colder, can't wait to toil under my car to change them. Got mine from www.sparkplugs.com

 

Check your local polaris dealer for plugs in stock.

 

NAPA carries them.

 

i think doing it from under the car is the hard way...

 

Spark plug gap should always be checked as a precaution, even if they are the correct plugs for your application. Plug gap should be .026" to .028" (Microsoft Word file) according to colder plug installation info on Vishnu site (thanks to Egan and BAN SUVS).

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