I was wondering how much boost I can run on the stock plugs in my evo9. I'm gonna be running 110 octane fuel for higher boost levels and using an AEM uego wideband to keep a/f's in check but I need to know when to change to a colder plug. Now from experience I know that a BPR7ES plug on an evo8 can handle 28 lbs of boost with no problem but what about the evo 9? I know that I have iridiums so am I ok for 25-28 lbs of boost on the stock range?
This is on the stock turbo btw. I'm doing TBE, cone intake filter, wideband, 255 pump, and AEM tru boost so I can tune for high boost(28lbs) and low boost(23lbs)

 

The usual "rule" is a 100whp gain = 1 step colder plugs. The colder iridium plugs carry a heavy price tag and you can get them from ExtremePSI.

 

I've ran 1 step colder on a moderate setup with stock turbo and cams..it was fine and allows for a little extra safety margin when boosting past 22psi. I didnt notice any low rpm/part throttle hesistation or anything.

 

Alright thanks for the help guys. Right now since I have no mods I'll be replacing them with stock ones or I may just try to clean them up a little. There's no corrosion on the electrode but there is a little deposit on the underside of the tip.

 

so what plugs should i get, im going to be at 22 psi, 91 octane, catback, dp, bc, fmic, licp, intake, o2 housing, tune, and i might get S1s

 

If you have IX, the stock iridium plug will work but you can also run a 1 step colder. If you are putting down 350+ then you should switch out to a 1 step colder plug.

 

k thanks

 

I would switch to one step colder if :
1. You lived in hot climates year-round.
2. You like to run your car hard daily.
3. Your car is tuned to the bare threshold of knock.
4. You are making more than 350 + whp consistently.

 

hum. oops im still on 7es plugs. heheeh. car never skips a beat