i just started getting a really bad misfire at wot so i was going to change out the plugs, should i go with a step colder spark plug? what plugs are you 450whp-500whp guys using?

i was going to buy the denso iriduim - IKH24 for evo9


John

 

You'll probably get flamed from a lot of guys for asking that question, but general rule of thumb us one step colder for approx 100hp over stock initially

 

Stay away from the Densos. My locals have nothing but trouble with them. If you have an IX, stick with OEM. For VIIIs, I prefer coppers which should be replaced often. 1 step colder isn't a bad idea, but the stock heat range can support that horsepower with no issues,.

 

thanks chu!

 

why should you stay away from Denso's ?

 

Like I said above, many of my friends who bought them for their cars had nothing but issues. Two of the cars misfired on idle. A few others misfires in the 5k range, almost as if the plugs went bad. We immediately threw on new oem plugs, and the cars ran perfectly again. A few of my friends are making 500whp on stock plugs. I will stand by OEM for the IX.

 

I'm making around 350whp at 24psi on stock turbo with the Denso IKH24s.

They work great for me and I change them about every 10k miles

 

I think plugs are a very misinformed technical part which many don't know alot about.

many people are in the 500+hp range on stock plugs... Often times you can visually inspect plugs and try to find the heat ring, discolorment around the prongs to see if you need to go colder from stock as the ring moves closer and closer to the tips.

Misfires can happen from many reasons and can be compensated by changing plugs, but if your below the 500hp range on stock plugs and have issues, odds are IMO you may have another issue. (tired coil, bad ground, something like that)

 

Or that the plugs are old...

 

i still use the stock NGK plugs in my car. i make a good bit of power too. going to a colder plug isnt needed until your making big power

 

why wouldnt u use densos? it could be there tune wasnt good and those plugs u put in didnt improve, i know from swapping my ngk bpr8es, for denso iw24 plugs...for the most part my car drives better even not being retuned after a copper to iridium one step colder swap...the idea of changing your copper plugs almost as much as an oil change isnt worth the 10, after 4 oil changes ur at the same price as a set of iridiums which u can go 30k plus on them...mine came pregapped at .024...no problems there pushin 26 psi peak on 91 octane.

 

I dont run anything but NGK in anything I own. For heat range, one step colder on pump gas and stock if on E85

 

I'm just speaking from personal experience here. The tune on the car was perfect, and ran oem plugs forever. But they got old, and needed to be replaced, and were replaced with Densos, which didn't work out.