I would put in the colder plugs. It's not just an issue of spark blowing out. The colder plug will pull more heat from the combustion chamber and reduce the risk of detonation. Most people are probably better sticking with stock or a "7" heat range NGK alternative for running moderate boost levels on lightly modded car, but if you are pushing the car hard (and it sounds like you might be with 345 whp) then the "8" is going to give you more consistent performance and a little insurance at the risk of fouling in daily driving if you do a lot of low RPM commuting with the car.

 

Stock heat range is "6" .... "7" to "8" are used for higher applications. If your making in between 300-400 bhp "7" heat range is still good unless if you prefer to use "8".

Here is some tech info from NGK in choosing the right spark plug for your application.

http://ngksparkplugs.com/techinfo/sp...000&country=US

I hope that would be useful enough.

 

OK, this is my question for you guys, If I have a EVO 05 with 8000 miles with the stock spark plugs(haven't change them yet) and the mods listed below, what spark plugs do you recommend installing?, Should I get the stock spark plugs again considering my mods?

Thanks!!

 

Warrtalon, you are right I got mislead by the info from Lancershop that's where I bought my BPR7EIX.

Here's a thread about plugs... you may wanna check it out -

https://www.evolutionm.net/forums/sh...ock+heat+range

 

NGK BPR7EIX would do just fine, you can gap it between .028 - .029 in.

Here's some installation info -

http://ngksparkplugs.com/techinfo/sp...300&country=US

 

Where are you getting your information? My understanding is that the stock heat range is 7.

 

my 05 has 5000 miles and right after I put in my 264s it started sputtering in the top of 3rd and 4th gear. Went to the 8s and the car runs real f-n good. I recommend this plug especially if you plan on running alot of race gas at the track. I think thats what fouls them so fast. Im just gonna keep an extra set on hand just in case.

 

This is what I use BPR7ES for daily driving gapped at .028. When I run higher boost on race gas I have to gap down to .024-25 otherwise I get a miss around 4000-4500. I normally use the BPR8ES on race gas but the local parts store has been out of these for a while.

You have to change copper plugs pretty often but they are very cheap. I usually change mine every oil change.

This topic has been covered many times..