More on plugs
Mick,
I am not surprised you saw an improvement in performance with fine wire plugs over your old massive electrodes fine wire plugs (regardless of the brand) will produce a hotter spark than massive electrode plugs every time. this is because iridium has a higher melting point than the massive electrode material and so can support a hotter spark without excessive wear. In order to create the greater spark the plug employs a bigger air gap (more resistance hence greater voltage build up to ionize the gap). Also teh smaller electrode does not shield the fuel air mixture from the spark.
As for testing the resistance that's fine, you chose tempest plugs and they require resistance tests, I only have a problem with testing champions which CANNOT be tested in this manner.
Creamie:
I wish you would back your arguments up with some reality, on the one hand you argue that extra voltage due to plug gap wears out the magneto faster on the other you argue that fine wires are better for your engine than masssives. Well guess what: fine wires have a greater gap and a higher discharge voltage than massive electrode plugs.
NGK suggests that excess voltage can damage a coil by overheating but that in order to do this (at least with their coils) they would require an air agp greater than 1 inch which does not occur with plugs.
And when you post the spurious blog post of a man (granted a switched on guy) connecting a TAZER to a plug as proof of your theories perhaps you could include the paragraph where he contacts the plug manufacturer and they say they would consider resistance testing: With a max resistance of 80,000Ohms!!!!!
Yr Right:
There are two reasons for the resistor: To prevent radio interference and to reduce something called capacitance after-firing, a condition where back EMF builds up in the lead shielding and then re-discharges across the spark gap after the firing sequence. The resistor in the plug ensures the back EMF discharges to ground via the shielding (easier path).