Which Spark Plugs to Run with forced induction

[quadcam boat]

I'm ready to go out and tune my engine. It is has a M90 Eaton running 8psi on a stock 1UZFE with an aftermarket computer and is fitted to a boat. The motor is a 1991 model. Do I need to change sparkplugs? I remember hearing something about moving 1 heat range cooler for forced induction. Also I am using Avgas at times, so won't be using platinum tip plugs as lead wrecks them.
Cheers
Andrew

 

[40GT]

At http://www.kennebell.net/faq/faq-answers2.htm they state " What spark plug should I run with a supercharger? One heat range cooler than stock. Denso Iridium is the best plug we've ever tested. Avoid Platinum plugs. Always set gaps at .035". Denso irridiums are factory gapped at .044"." At http://www.densoiridium.com/faq.php they state " A good, general rule of thumb is ....for every 75 to 100 hp you add to your engine, you may go to the next colder step. "
Hope this helps

 

[quadcam boat]

Thanks,
that sorts me out!!
Andrew

 

[Lextreme II]

40GT,

What NGK IX Series? They are alot cheaper version of Denso. The Denso Iridium is about 13 USD each and NGK Iridium (IX) is about 6 USD. I am trying to run 15 psi, but at 9 psi, the car seen to low down. I think its partial due to ignition and spark. What is your recommendation? MSD DIS-4 will be install next week. Meanwhile need your advice on spark type and gapping for FI (15 psi)

 

[Red Supra]

Hi boost street driven 2jz usually run NGK 3330 gapped at .028 -.025, They come pre-gapped at about .032 They are pretty cheap at about 3 dollars a peice and last a while as well. The iridium plugs are very sensitive and are prone to fouling out if you run a richer than stoich a/f mixture at idle and cruise. For guys with near stock sized injectors it's not an issue but ones who have big injectors and can't get a 14.7 a/f idle you end up going through a lot of em.
Using a colder plug will have a negative effect on idle quality and engine smoothness as well. With 1 step colder than stock you wont really notice it but once you get 2 or 3 steps colder watch out!

A set of copper plugs one step colder than stock will be a good starting point while you're getting the tuning done. Once you're pretty close to dialing in correct a/f ratios you can switch to iridiums and see how long they last you.