Originally Posted by Omniscient
They even gap there iridium plugs to .3 for FI tytness.
Well that's right about where they should be gapped.
Originally Posted by 98CoupeV6
I've always read that copper is best for low compression/NA engines and iridium is more suited to turbocharged/high compression engines. Enlighten me sir?
Copper is a better thermal conductor, but it has a lower melting point. Since the iridium plugs have a higher melting point, they can have a sharper electrode tip. Sharper tip = stronger spark, but it holds heat longer. In FI engines where detonation is always a risk, copper plugs with a wider electrode are better. Since the electrode is wider, it has more surface area and cools off faster..so it won't stay hot for very long. You want the plug to cool off faster in an FI motor, because the hotter it is, the closer you are to detonation. Also, the bigger the electrode tip, the more current the plug can flow...which is better suited to high power fi/nitrous applications.
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