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sparkplugs.com »
https://forums.nicoclub.com/sparkplugs-com-u23266.html
Mon Jun 20, 2005 7:21 am
from our website:"Some combustion chamber designs (such as a rotary motor) require that the spark plugs have the ground electrode placed to the side of the center electrode rather than below as on a traditional plug (see photo). This firing tip design tends to erode the tip of the ground electrode faster than a traditional plug, erosion at these points creates a larger gap between the center and ground electrodes causing plug misfire. Thus by having more ground electrodes you extend plug life. It is important to note that multi-ground does not mean multi-spark, there will still only be one spark at a time. Therefore a multi-ground plug will not perform any better and may actually perform worse than a traditional plug, unless the engine is designed for a multiple ground plug."
Its also not recommended to gap multi-ground plugs