[BLSTIC]

So once upon a time I side-gapped the (copper-core equivalent) plugs on my 2NZ Toyota Echo while searching for a load-dependent misfire that turned out to be fuel pressure. Surprisingly it did *something*, in that it was able to handle marginally higher loads (and produce equally marginally more torque at lower loads) before misfire, implying that I had indeed improved spark ignition. Eventually I tracked down the problem, and the plugs stayed in there until it started misfiring again. It turns out that they wore out to a 1.5mm gap before misfiring.

Now I *thought* 1.5mm was guaranteed bad idea on anything, but I have 18 year old coils firing a 1.5mm gap with 10.5:1 compression, and they only just began to misfire. Meaning that at 1.495mm they were just dandy. So what gives? And how can I abuse this effect?

I've looked into electric theory and it states that curved surfaces tend to build charge and pointy surfaces tend to allow it to arc. The sparking region of a typical plug is the end of the electrode and the side of the ground strap, a rectangle on one side and a circle on the other. Both flat areas equidistant apart. You'll note that when a plug is new it has sharp edges, and when it is worn it has rounded edges. You'll also note that pointy iridium plugs run larger gaps.

So if I were to take side-gapping to the extreme, by rounding off the opposite side of the electrode, grinding the ground-strap-facing side to a point, sidegapping the ground strap and performing the same no-edges-that-arent-facing-the-spark ritual, how much gap could I run without misfire? And how much would that actually help?