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In the process of chaning sparkplugs - Advice needed

880 Views 5 Replies 3 Participants Last post by  ncno
So I'm currently changing sparkplugs on my RB25DET.
It's first time changing them, (atleast for me) and since I don't know when they were last changed, I figured it was a good idea.
I've taken the old ones out and put the new ones in, but now I'm not totally confident wether it'll run better or not with the new ones.

I read around the net and came to the conclusion that NGK BCPR6E was the way to go..
It turned out that the old ones were NGK Iridium BKR8EIX - I've thought that it's quite a difference in heat range, and now I want to be sure I've chosen the right sparkplugs before firing her up.
The BCPR6E are currently installed, but haven't started the engine yet.

Regarding mods it has the following:
3" custom built pipe from the turbo back (no cat)
Large open air-intake
HKS FconS ECU (mapped by local in the UK before I got the car)
HKS Blowoff
HKS EVC set at 0,8 bar
Fuel Pressure Regulator

I think that's all which have been altered and could have an impact regarding the combustion.

I've taken a few pictures of the old plugs. Keep in mind that the 2 last times she has been running has been in idle for about 2 mins each.

So, are the sparkplugs I've chosen the right ones, or should I go up in heatrange? (Perhaps Iridium ones again) Thanks in advance.
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1 - 6 of 6 Posts
I use NGK grade 7's in mine. Make sure they are gapped to 0.8mm and see how you go :)
Quite sure they're 8 mm's. I'll measure them before starting up just to make sure.
Do you think the grade 6 will go? If no one is going to tell me otherwise, I guess I'll have a go and afterwards inspect the plugs.
I had grade 6 in mine when it was standard with no problems, it's when you star to up the boost etc you need colder grades. Like i said chuck them in and see what happens :)
Heatrange 5 is factory for the R33 25DET (6 is factory on the NEO).... 6 should be fine for those mods.
....and yes, BCPR6ES is pregapped to 0.8mm :)
Great, thanks.
Seems like i'm running rich though. The old plugs are pretty messy and even has some pits and such from unburnt fuel. Guess I'll have a remap or even a new ECU + wiring. Apparently the FconS is pretty restricted.
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