Which plugs are best for performance?
I took a more scientific approach to this question a few years back. I compared the primary resistance in ohms of new 4 each AC, Champion, Autolite, and NGKs all same application for a 340. Resistance values will give you an idea of the consistency and spark energy going to the cylinders. Champions were the highest resistance, AC next, then autolite finally NGK. Champions varied all over the place between 10 Kohm up to 20 Kohms. AC were lower on average but still in the 10 +Kohm range, autolites were between 5 and 10 Kohm. NGKs were consistently very close to 5Kohms +/- 500 ohms. Guess which plugs I recommend ?
I'm not an electrical genius, but that measurement, in my limited pea-brain means nothing. Any good coil will drive thru that like it wasn't even there. In fact it may actually drive the coil into generating a few more volts, and that would only increase the intensity of the spark kernal, just as the rotor gap does. I mean put an ohmmeter across that rotor-gap and see if you can measure it. I bet it reads open circuit. And yet the spark gets across it somehow,lol.
>I'm not saying your test is somehow invalid, cuz it does tell us a little bit about the plug. And on snowmobiles which have notoriously marginal coils,( unlike outboard marine engines, that can be used to weld with),or other small engines, I install NGKs only, cuz they flat-out work, and flat-out work longer.In metric motorcycles, they are also the plugs of choice, cuz again, the coils are marginal. And when it comes to non-Marine apps and CDI coils, NGKs pretty much have to go in.
>A real coil will fire any old plug, under just about any old conditions, short of being shorted. I occasionally wonder how big the gaps are getting to be on my 100,000 mile, 16 year old RN12YCs.
But hey, it starts, runs and smokes the tires to 7000 in two,sometimes 3 gears, so......what more could I want? lol
