spark plugs upgrade
 

im after upgrading my spark plugs. currently got pfr6b in. which ngk plugs can i upgrade to?

NGK7B's.modded motor
NGK8B's extreme modded motor :)

How do you define an extreme modded motor?

you tell me ??

do you have one ??

check your plugs LOL

Don't have one at the moment but looking to tune it a fair bit, would it do any harm to have the second set you mentioned?

Can't get NGK PFR8B to my knowledge. NGK BKR8EIX are one option (cheap) or NGK Racing 7434-8. I would suggest an 8 for over 350 BHP, a 7 for 250 to 350.

STI gives as uprated spark plugs the Iridiums BKR7EIX for WRX and STI both with 0,6mm gap, I don't know about heavy modded engines but they work great in a friend's STI with 1,45bar boost and more than 350ps!

http://www.subaru-sti.co.jp/parts/gd.../image/3-2.jpg

JIM

Thanks John for just correcting me on that plug number i must have had a dizzy moment :)
Just a thought on heat ranges basically,would'nt have said an upgrade more like a precaution for your tuned engine.

NGK PFR7B are a good reliable plug for reasonable cost and operated well for me. Unfortunately around 500 bhp I was persuaded to try an "upgrade" to HKS 35i. Broke the electrode insulator on one and heard of others that broke around the same time.

Aren't the HKS plugs rebadged Denso plugs anyway?



With regards to the original question whats the point in putting a colder plug into a standard engine?

Just bought NGK 7B's

Modded STi.

MB

I had 7bs in mine when it was about 310bhp, so only mildly modded. It cured a slight missfire, but I didn't need them until the boost was cranked up. Save the £30 for Optimax until you need them mate.

JB is correct, NGK PFR8Bs were discontinued.
Closest replacement I could find is the NGK 7435-8.

I found www.spark-plugs.co.uk very knowledgable and helpful

The 8's aren't too good when cold apparently, so unless you need them, stick with the 7's and replace a bit more frequently than the recommended 40/50k interval.

MB

Could someone let me know whether the NGK Iridium IX plugs I have in mine are any good?

Well the BKR7EIX are shown in post #7 by Jim and sold as STi. I have some BKR8EIX to try at some point as well - they are much much cheaper than the R7434-8.

...and yankies swear on them John!

Do you mean BKR7EIX-11 John ?

Don't know about the -11, Jim? My 8s are in my glovebox, I'll check when I can.

11s have large gap for our purpose even with highly modified engines, you need them with max 0,8, have in mind STIs have 0,6 and work fine!
JIM

My Gosh, blimey, really that long?
 

Is the recommended change interval with the 6b's and 7b's really 40/50k?

How often should I be changing them in my MY98 WRX? 320hp (I think this counts as modded!)

Your not wrong..mine broke. One plug tip fell apart and we were lucky to get away without any major damage.

Now running NGK PFR7B at 300bhp / 300 nm - no probs yet! :)

Normal life is over 60k, but if its modded it would be wise to change them a bit more regularly. The cost of this far outweighs any other consequence :)

For most of us, 40k miles is a good 3-4 years, so £35 for plugs isn't worth thinking about...

MB

Cheers Mark!