Michael D. Porter wrote:
>
> Lars G. Johnsen wrote:
> >
> > Know that there are other new and improved plug designs out on the
> > market: anyone had any experience with those?
>
> When the price of platinum plugs came down a bit from `80s prices, I
> bought a set of those and am still running them. As for odd-patterned
> ground electrodes, there's not much to commend or abuse them, I suppose.
> There was a thread on the diy_efi list recently about Splitfires,
> commenting on a US ruling that the Splitfire manufacturer cease and
> desist advertising power, mileage and emissions gains, since those were
> not proven in practice.
>
> In theory, an arc traveling from the center electrode to the ground
> electrode will deposit metal from one to the other, and corona theory
> says that electron travel depends considerably on the sharpness of the
> emitting electrode, because of the concentration of charge on a sharp
> point (have seen this to be true in the lab). More electrodes would seem
> to make an arc more likely to happen, but I have the feeling
> (unsubstantiated by data) that multiple electrodes probably erode and
> thus lose good electrical surface at about the same rate, so the
> difference in performance is small. As well, there may be disruptions of
> the flame front by multiple electrodes, so having a spark because of
> multiple ground electrodes may not translate to far better performance.
>
> However, I will mention one curious case. Every once in a while, when I
> worked at a Toyota garage, a Tercel with a 3AC engine would come in on
> the hook, dead as a doornail. The owner would invariably say, "I just
> had it tuned up a few days ago." Here? "Uh, no," the owner would say. In
> every case, there were Champion plugs installed, of the correct heat
> range and nose configuration as the stock Nippondenso plug. They simply
> refused to start the car, however. When the plugs were removed, they
> showed about as much wear and as many deposits as one would expect from
> any other plug with that amount of use. None had severe blistering or
> melted electrodes or charcoal on the insulator which might indicate the
> conversion chart was incorrect. They simply did not work.
>
> In every case, installing new OEM Nippondenso plups solved the problem.
> In theory, the only discernable difference in the design of the plugs
> was the ground electrode. Champs have what one would describe as a
> traditional electrode, while the Nippondenso's had a square groove cut
> in the underside of the ground electrode. The theory says arcs start and
> travel to sharp edges, and the groove in the electrode provided double
> the sharp edges of a standard electrode. The reason for the plugs'
> failure may have been something simple, but the answer evaded me. I even
> saved the plugs and put them in other engines, just to see if the
> problem traveled with the plugs, and it did not. I suspect that it had
> something to do with one or more of three things. One, the plugs were a
> standard Champ design from the days prior to HEI ignitions, and the
> plug's insulation had broken down and tracked to ground (not likely,
> since they worked in other cars with HEI ignitions). Two, the groove in
> the OEM plug did make a difference, for theoretical reasons, and three,
> there was something about the engine's combustion chamber shape which
> made the Champion plug ill-suited for the application. Never did
> definitively find out.
> <g>
>
> Cheers.
>
> --
> My other Triumph doesn't run, either....
In 77/78... I restored my first TR 4A... in the years following... I was
a nut... a perfectionist... I rebuilt the motor... high compression
forged aluminum pistons, high lift Norris cam, heavy valves springs,
chrome-molly push rods... grade 8 bolts everywhere... etc. etc....
MEANWHILE.. I kept experimenting with spark plugs... I tried various
heat ranges... I tried the fanciest... most expensive... racing plugs...
etc. etc. etc..... I was a teenager... sure... and maybe I didn't do
things very controled... nor very scientifically.... but...
In the end....
After a couple years of changing plugs weekly/monthly....
I found that the standard champion plug held up the longest... others
seemed better at first... but generally fouled, wore out.. etc...)
I've stuck with standard Champion plugs ever since.
Maybe I'll change to something else when I really hear something
earthshaking... but the Champions hold up (for me, at least) and they're
cheap! : )
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