ive read the ngk IK22 are what most run with a 15% pulley. is this the common plug for 17 and 19% too? at what point do you need colder? I guess what im asking is not just putting in plugs because you think it may need them but what boost pressure should you and with what. ----------------------after all the tuning that goes on here SOMEONE out there should have some sort or data other that opinion. thanks guy/gals

 

there are plenty of threads on this , just search, it is also a personel preference.
IK22 would be Denso not NGK, the IK22 are one step colder than stock. NGK also has these and then you get to choose platinum or iridium, or not? The factory uses NGK one step colder for the JCW package. I am JCW and use NGK iridium one step colder than stock JCW.

 

What I think that the OP is asking is how would one know if they needed colder plugs? Is there any harm in going colder?

 

Unfortunately the answer is 'it depends'. Mfg tolerances, varying driving styles and driving conditions mean that there is no one 'answer'.
If your plugs are running too hot (tough to describe, see pics here), you need colder, if too cold (fouled with oil or carbon), you need hotter.

With smaller pullies you MAY be better off with one or two ranges colder than stock as the higher cylinder pressures will generate more heat.

Yes, if the plug is too cold for the application they can foul, or not burn the fuel as efficiently as a hotter plug.

 

Good info on heat rating. As well as general plug info.
http://www.ngksparkplugs.com/tech_su...2.asp?mode=nml

I'd go with the one step colder (IK22's or equivalent). Preferably the Iridium NGK's as they are less prone to back out of the engine.

 

Wow! Thanks for the plug education. Seriously, this is very helpful. It makes me want to pull out the plugs to check them out since I had a Jan tune a while ago and he talked about going one step colder but we didn't do it at the time. Maybe I'll check them this weekend and see how they compare to the pictures.

Thanks again!
Darren

 

I run NGK, two steps colder .

 

Like it was posted you need to look at the color of the ceramic. Gunmetal grey is what your looking for but to see the true color the motor has to be shut off in your power band. (Best done at the track!) then pull the plugs. Black to cold white to hot gun metal gray good.