1 step colder spark plugs

[RS12Turbo]

Just curious, at what point should I consider going one step colder with the spark plugs?I'm currently running 12-13 psi on a t25g with 3" exhaust, walbro 255, front mount, with NGK "6" heat range coppers.I have a set of NGK "7" heat range iridiums waiting to go in......but just not sure if I need them at this point.Thanks

[themadscientist]

I still run factory-recommended heat range on my plugs. If you are seeing signs of detonation I would go a step colder but otherwise they would just be a PITA fouling up during stop and go driving.

[float_6969]

Don't fix it if it ain't broke. I think many people step down to a colder plug way before they need to. As TMS said, it's just going to make them foul up.

[RS12Turbo]

Hmmmm, good to know, thanks guys......Just curious though......at what level should 7's be used? In the "part #/ cross over" thread, it list using 6's for standard engines, and 7's for lightly modded engines.......

[float_6969]

I've got the 7 heat range iridium plugs in my CA and at 10psi daily they don't stay clean like they should.

when I was running the GT28R at 7psi it was the same deal.

I would guess that if you're under the 250hp mark, you don't need them. Don't take that as the gospel though, as I've never experimented with it.

[boost_boy]

I agree with float on this one. The 7s tend to foul a lot faster than the 6s and for every customer's car I've thrown them in, they say the same thing. So until you start running 25+psi of boost through your engine, the NGK BCPR6ES-11s will be just fine; or whatever the hell they are in iridium brand.

Dee

[rico05]

I tried the 7s with my T25G at the same boost level, and they just fouled. Stick with the 6s.

[sideways danny]

I've run 7s for years without any issue, and always fitted them to customrs cars. a lot of people really do run far to cold plugs. some use IQ27 Denso plugs which is equivalent to 9s!!!!!! they really do coke up badly

[mikesim]

my 7's fouled on 14psi of boost on a GT28R. i went back to 6's this year and haven't had any problems, but i also am tuned for 94 octane.