RB25 E85 flex tune spark plugs

[smadayar]

Hello, had my car tuned on 98  and E85 (470hp 19psi) and want some advise on spark plugs. I currently have BCPR6ES gapped down to 0.6mm  using splitfire coils. This setup has no issue with missfire at full throttle on both fuels. But low load has abit of missfire on E85 and even more on 98 which I believe is due to the gap size. Can anyone confirm and advise on a better spark plug combination of any?

 

Cheers

[GTSBoy]

It's not the plugs you need to change, apart from the gap. And if the Splitfires won't support a larger gap, then you need bigger coils. Small upgrade to Yaris type or large upgrade to R35 type.

[WR33KD]

At 470hp you shouldn’t be gapping them at all. Could change the plug to R5671A-8. There a ngk race plug that I run, 28psi on 98 with splitfire coils no problems. The plug your using did cause me a misfire up around the 22-25psi but once changed it’s all good.

[Dose Pipe Sutututu]

Do you have a wideband? I wouldn't be surprised if it's a misfire due to a lean condition.

At 1.3bar of boost, 0.6mm gap and Splitfires are a walk in the park. You could run 0.8mm gap and still be fine.

[burn4005]

Denso IK01-24 or NGK R7434-8.

best plugs out there and a lot cheaper than a new set of coils. fine tip iridium.

I've had a set for 2 years in an 780hp rb26 and they're still perfect.

[iruvyouskyrine]

51 minutes ago, burn4005 said:

Denso IK01-24 or NGK R7434-8.

best plugs out there and a lot cheaper than a new set of coils. fine tip iridium.

I've had a set for 2 years in an 780hp rb26 and they're still perfect.

Was curious how much the NGK racing plugs were, I think i may hold off on purchsae

[GTSBoy]

It might be cheaper if you buy 6.

[burn4005]

RHD Japan are the cheapest I've found.

[BK]

They definitely are, but it's really only cost effective bundling with other stuff you order. I run the R7436-8 (53mm old JIS length like bcpr) as it is actually the correct length plug for RB26, not the R7434-8 (50.5mm ISO length like bkr) which is shorter. There's 2.5mm difference in height between them and the old JIS length fits a little better into your coilpacks. Sometimes it's an issue, sometimes not, but the 26 is supposed to have the 53mm length FYI. Fwiw though yeah the R7434/36 is the best plug out there - lowered iridium centre electrode and platinum ground electrode. But at around $50 per unit they'd wanna be...

I've attached the NGK race catalogue for the complete range available, as it's totally separate to the normal NGK site catalogue.

That said, the Op RB25 shouldn't require NGK race plugs though, or a heat range of colder than a 6 or 7 as you don't want be colder than you need to be. Gaps around 0.8mm should be fine too, so maybe 0.6mm is actually a bit small creating a weak spark. Maybe the plugs are just fouled up causing an occasional misfire ?

0.6mm does seems a bit on the small side no ?

NGK_Race_Plugs.pdf

[burn4005]

Good pickup @BK I'm using R35 coils hence the ISO version.

Forgot about that difference!