I know this has been discussed many many times but I cant find the right answer in the search. So, I'm making another thread.

I tried PMing Ya at IP to find out what NGK copper sparkplugs they use on their very high HP S's and race car but he hasnt gotten back to me. So, I am asking you guys.

I have been running the NGK BKR8EIX iridiums for a while with no problems gapped at .030". These may be good for most on gas but I am switching to e85, which takes more demand of the coils to fire. My tuner/friend wants me to switch to the NGK coppers because they will have a hotter spark for the e85 and copper is the best even though they dont last as long.

Does anyone know what NGK copper plugs that IP uses for big power, 700+ whp? I knew a long time ago but cant remember. I think it was a 4*** number.

Thanks guys.

And no, I am not going with the 7173's. They suck bad on my car.

 

I am running the Iridiums and E85. I am not at your powerlevels tho. I have had no problems at all up to 420whp.
Would it be unthinkable that a sparkupgrade is needed for those powerlevels on E85? I am just speculating here.

 

5671A-9 or 5671A-10 depending on what heat range you're looking for.

 

if you don't mind explaining, what happened to your car when you ran the 7173's??

 

Thanks but I should have mentioned that I'm looking for 8's. I think 9's will be too cold.

 

I had spark blowout even gapped down to .023" and it had idle issues and driving blips.

 

Well, cooper will have the best and strongest spark for e85. Iridium plugs are platinum plugs coated with iridium to help with longevity I believe. Platinum or iridium doesnt have as strong of a spark as copper.

 

R5671A-8

 

Or if you're one of "those people" that insist you need a resistor plug BKR8E-11

 

Oh, I didnt know they had those. Have these been proven to work well with high horsepower S's? Are the R5671A-8's resistor plugs like the BKR8EIX iridiums?

Wait, those R5671A-8's are the 4554's arent they? I think those are the ones I was looking for and what IP uses. Is this correct? This seems like the number Ya gave me a few years back. If these are what I'm thinking about, it looks like they are non resistor. Wont this have problems like the 7173's did on my car?