Scott,
I haven't looked for any online explanations for plug ratings, but I can
give a thumbnail answer.
In proper operation, a spark plug is not supposed to ignite the fuel-air
mix until it "sparks". In an ideal situation the flame is started at just
the optimum time and progresses quickly.
What can happen is that if it's a "hotter" plug than the application needs
then the ceramic and the electrodes get hot enough to ignite the mix
prematurely, acting like the glow plug in a diesel.
How do you make a spark plug cooler (at time of manufacture, of course)??
The spark plug is cooled by heat transfer from the ceramic to the metal
portion that threads into the cylinder head. So by changing the geometry
of the plug ceramic the manufacturers can tweak how quickly the plug cools
- in a relative sense- or how much heat they retain between firing cycles.
If you could cross section a "hot" plug you'd see the ceramic is a long
thin cone with the contact point to the metal far up the spark plug body.
A "cooler" plug has more ceramic and contacts down closer to the electrode
end.
In the car, if the plug is too hot you'll tend to get pre-ignition under
extreme conditions (pinging/pinking) which will do all kinds of neat
damage. If the plug is too cool it won't burn off the carbon buildup and
eventually foul. A perfect plug is one that is cool enough to not ping
under full load, but good enough to keep firing under cooler conditions.
HTH
Cheers,
Jim
Dallas TX
> <<the best race plug ever made.>>
>
> OK, I'll bite -- so what makes a plug a good "race plug"? The spark plugs
> (like a large, but decreasing, number of parts of our cars) have always
> been a mystery to me. What makes one hotter and one cooler? What do you
> see on the end of the plug that tells you whether you need hotter or
> cooler? Are there any recommended reading resources out there?
>
> Scott (B.)
>
> -----Original Message-----
> From: owner-fot@Autox.Team.Net [mailto:owner-fot@Autox.Team.Net]On
> Behalf Of Ted Schumacher
> Sent: Tuesday, October 26, 2004 7:16 AM
> To: Herald948@aol.com
> Cc: fot@Autox.Team.Net
> Subject: Re: Interesting message
>
>
> Andy, we still have Champion gold paladium plugs in stock. Probably the
> best race plug ever made. Plug numbers end in "G" to denote the gold
> paladium. A real race only plug. Ted
>
> Herald948@aol.com wrote:
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