Best plugs for Supercharger?

[Joel]

Dan
I recently fitted a set of Denso Iridium IK16 plugs to my N/A GTS. This is as recommended by Denso. Initially I noticed a good light throttle smoothness, and good throttle response. However after about 300 miles highway driving and a few 1/4 mile passes the performance seemed to drop, showing as a SOTP feel and a deterioration of times. Another 300 miles of highway had the motor running poorly at light throttle. A change back to std Champions cured the problem. The IK16 plugs project less far into the chamber and I wonder if they are firing in some kind of boundary layer which affects the combustion process, particularly under light throttle lean mixture conditions.
BTW, hurry up with that supercharger

 

[David]

Dan,

I didn't use the following plugs on my Viper, but I did use them on an aftermarket turbocharged engine. I had a Saturn SL2 -- a nice but powerless American compact. I put a turbocharger on it using a custom exhaust manifold with boost set around 5 to 7 PSI. A/F was handled by an add-on fuel pressure regulator. I initially used standard plugs a few heat ranges colder than stock. I found that the gaps would quickly burn open and the electrodes wouldn't last long -- even when the ceramic insulators looked like the plug was too cold (dark brown to black). I switched to Beru Silverstone plugs (available at www.nology.com) at a standard stock heat range. Those plugs used silver electrodes to better conduct away the heat and they lasted about 30K miles. I gapped the plugs down to 28 thousandths to insure that the air/fuel mix would "light" under boost. I only had to re-gap those plugs once during that time. I did try their fancy Nology spark plug wire (it basically acts as a capacitor for a better spark discharge), but didn't notice much improvement. I guess that figures seeing that I was using such a small gap. I believe the standard gap for that car was around 40 thousandths.

Hope this helps.
-David