Glow Plug Heat Ranges
 

I have been searching the rctech forums for information about when to run a cold plug, what to get for better idling, longevity, ease of tuning, and better starting, etc. but I have been searching for a while and havent found a definite answer. Say an engine doesnt idle very long, what heat range should it be? If the engien is hard to tune, what heat range then? I am going to get a v-spec and going to run the OS P3 plugs. Since this is an ultra hot plug, what would happen if I would go to a medium or cold plug?

I wish I could answer all your questions but I cant..The one thing I can tell you with confidence is that the Only plug you should ever run in the V-spec is the P3..seems everything else is just not right..Many people I know have tried several different plugs, and the bottom line is always P3. I never bothered to try anything different and never had a problem. that's in Arizona with very low humidity, and elevation ambient temps are between 50 degrees at night and 175 in the day:D

The nicer the day the colder the plug. The colder the plug the smaller the tuning window (harder to tune). The colder the plug the more power you can potentially make.

OS vspec based engines I would recommend starting with a P4 if you are someone who can tune your own engine. If you're a beginner you should try a P3 and tune on the conservative side.

It gets to about -100+ out in the summer. Since this is my first race engine, I will get a couple P3s. What do you mean by tune on the consertative side (run it on the rich side right?)? So does going to a hotter plug have some of the effects of a lower oil content, to where it is more risky to run leaner?

Yes on the rich side, but just make sure your getting up to temp. You wanna run at least 220*. So i guess when i say "rich side" i mean burn more fuel. running to cold can put unwanted strain on this engines. The reason colder plugs make more power is cause it's a more efficient burn (less fuel) < harder to tune
If your in a HI humidity area then you should defiantly stick with the P3. When your tuning confidence builds (on a nice day) try a P4. ;)