ref the post from a week or so ago.

00MY UK car with approx 300PS. STi plugs the best to go for? No.7 heat rating?

Cheers!

 

For a MY98 with PE ECU and T75 downpipe (256PS) PE recommended using 'normal' platignum plugs, but coming down to a No 6 heat range.

Hope this helps,

Graham

 

Subaru's workshop manual recommend using an NGK 6 for the turbo engine. Some would agree that this is a little too hot. Speak to Andy at BRD and get home HKS S35i Iridium's. They are about the same as a number 7, and saw me ok running 18PSI boost. They also seemed to be ok running 1.6BAR.

Dan

 

MY01 STI RA. Engine and exhaust unmodified.

Currently running NGK "Iriway" #8. So far no fouling, misfires etc. I blew one Denso Iridium IK24 on WOT gear 4 just as the boost hit max (~4500rpm), car became a 3 cylinder boxer. Anyone contemplating using Denso's, proceed with Caution.

That was why I switched back to NGK. They're the OEM for the STI aftermarket iridium plugs (check out www.subaru-sti.co.jp, use a translator; or www.japanparts.com), and they recommend a #8 heat range for rally.

Maybe the tropical climate allows me to get away with #8 on a std engine, so those in temperate weathers may not want to go this cold.

 

Correction:
The plug I blew was an IK22, supposedly equivelent to a NGK #7. That was why I went back to NGK, and one step colder - #8!