[wizkid1358]

With my application I am currently running an NGK TR8IX plug. I was thinking about going to non projected tip plugs as they are said to be better with high compression and boost. Now the problem is the only plug I can get with non projected tip, NGK 8 heat range, in 14mm thread, .708in reach, with a tapered seat is a non resistor plug. I would like to stick to resistor plugs to avoid the RFI problems. If someone has experience tuning boosted engines do you find it's more important to have a colder heat range plug or to run a non-projected tip? This is for a vehicle that sees a lot of street use.

[wizkid1358]

Well after experimenting with BR7 plugs I found the TR8 plugs can take more timing so it seems the heat range matters more than the non projected tip. It also seems to idle better and run better outside of boost with the projected tips.

[cgrey8]

That's interesting information. I don't know that I would've predicted that.

I vaguely recall a thread or two from the past suggesting that boosted applications don't like platinum-tipped plugs. And while I found it surprising at the time, I guess it does kinda make sense given CAT converters also tend to use platinum as a catalyst. I just always assumed it was a different alloy than what's used in a CAT. But I guess if pure platinum has catalyst-properties at all, then it would make sense that the presence of it could cause engines to begin combustion before a spark has occurred particularly under the conditions of heat, pressure, and abundance of fuel.

In my NA engine, I run a colder copper plug than the OEM 97-01 Explorer 5.0L takes. Although I don't honestly know if it's doing anything beneficial or not. I did it because I have cast heads and over 10:1 CR. My hope was to allow for a tad more spark advance without detonation. Although I can't say I recalled any noticeable benefit when I changed the plugs. But once they were in, I saw no reason, to swap them again since they had no ill effects.

I've always had to add a fair amount of spark retard based on ECT as temps rise above 185. TBO, I probably should be running a 160 degree Tstat instead of a 180. I upped it just because the heater couldn't keep the cab warm when the outside temps get in the 20s and teens with a 160 degree Tstat. So last time I had the 160 Tstat fail (locked-open), I installed a 180. I made the mistake of buying one of those fail-open Tstats thinking that would be safer. But all it did was keep locking itself open on hot days. First time it did it, I just manually unlocked it and reinstalled it. Not 2 weeks later, it did it again...another reason why the 160 probably didn't warm the truck very well the winter (it was probably locked-open). When I replaced it, I did so in frustration and put the 180 in. I probably would've been fine installing a "normal" 160 Tstat in retrospect. Live-n-learn...

[jsa]

Heat range of the plug is important as combustion temps increase with boost.

The faster the combustion burn, the less spark advance required for optimum performance. Use whichever tip type requires the least advance to give equivalent performance.


If your platinum plug tips are getting to cat temps, colder plugs would be in order. The Cosworth YB engines are platinum plug from the factory. Many run iridium plugs plugs in them.