The B9HS are considered an open style, not projected tip, and work where you have significant room between piston top and negative electrode, as in our chamber designs allow.
The "C" originally signified 'compact" negative electrode, almost recessed, to allow for shallower chambers, piston top closer to negative electrode. Over the years, the 'C' has taken on different names, such as 'competition', etc. They work well for the most part.
The "V" signifies a very small diameter center electrode, to concentrate the spark at a smaller firing point. when spark amperage is delivered in a regular diameter center electrode, it gets to the end of the positive electrode, and takes a millisecond to "figure out" the closest point to make the arc to the negative electrode. The fine wire ones have an easier, shorter time of it. Also, the positive electrode was designed to actually melt away of the plug temps were too high, to indicate the plug heat range was wrong. Trimming the negative electrode into a rounded point side to side, will also help the V plugs, NOT J GAPPING, just pointed tipping the negative electrode.
A projected tip plug is one that has the negative and positive electrodes placed further out of the end of the plug jacket, to allow for fuel molecules to migrate between the electrodes easier, from leaner mixtures for emissions applications. Projected tip plugs work well when they are applied correctly, and some few, not many two strokes can benefit from them, when they are run at the ragged edge of jetting leanness. Projected tip plugs also run a bit cooler, from having the electrodes more exposed to incoming cooling air/fuel mixtures, so, some very small detonation help can be realized, but mostly, not worth the effort to tune engine to them alone.
The older "R" series plugs are really different. These plugs have no electrodes protruding out of the jacket, and the negative electrode is simply a section of wire, placed through a hole in the side of the jacket, adjusted with a tool to push it in or out from the positive electrode. These plugs run dead cold, and are not easy to keep from fouling. they are wide open stuff, not suited for anything but long circuit, full throttle road, and, drag racing.
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