Apologies for having to bring up this "old as dirt" subject but I cannot find any info with the crappy search engine on this website
What spark plug do y'all prefer in a high boost 2.2 / 2.5?
I used to run NGK GR5 spark plugs per the general consensus (and Ed Peters if I recall correctly) for high boost engines but cannot find them in town unless I special order and wait a week. One store sold me a Champion RN14YC as an equivalent but I don't believe it, 14 is a bit hot and a cross reference at the Champion home page shows the heat level of an eleven or twelve being equivalent to the GR5 heat level. I remember running Champion RN9YC in years past but maybe that was when I was sinking my automotive education monies into that '69 Dodge 340 engine.
My recollection is to ignore all Platinum coated plugs in our applications. Would we want to go cooler or hotter?
I use RN9YC's with stock gap. This is stock timing at 28 psi, and the plugs always look perfect. My intercooler is near 100% efficient though, and I have water injection, plenty of fuel, and a wideband, so I think I have zero detonation issues.
I run RN9YC's also, but with a slightly tighter gap than stock. I'm at 20 psi, with stock stuff at the moment (other than the basic 3 bar requirements, of course). I tuned it to not set off the knock light without water/meth, but I run a little bit for added insurance. The plugs look fine when I check them periodically. It has been my daily driver for the last several years also if that helps.
OK thank you all for your comments! I found another long tread on this website about plugs and have adjusted a set of RN9YC to .035 inch gap, installed them, and am very satisfied that the 2.5TII in my omni now runs fine.
Thanks for that Mr. Pope- i understand orienting the gap in special orientation with respect to the intake valve but hadn't considered modifying the gap to accommodate extra high velocities in the combustion chamber. We have family in Colfax if you are near there.