Thanks guys for the help with this one, but it's real hard to dispell my customers ideas that higher compression equals more heat (as well as more power) things like the following aren't helping things...you'd think NGK would be more careful about such "blanket statements.
From this web site:
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Below is a list of some of the possible external influences on a spark plug's operating temperatures. The following symptoms or conditions may have an effect on the actual temperature of the spark plug. The spark plug cannot create these conditions, but it must be able to cope with the levels of heat...if not, the performance will suffer and engine damage can occur.
Air/Fuel Mixtures seriously affect engine performance and spark plug operating temperatures.
Rich air/fuel mixtures cause tip temperature to drop, causing fouling and poor driveability
Lean air/fuel mixtures cause plug tip and cylinder temperature to increase, resulting in pre-ignition, detonation, and possibly serious spark plug and engine damage
It is important to read spark plugs many times during the tuning process to achieve the optimum air/ fuel mixture
Higher Compression Ratios/Forced Induction will elevate spark plug tip and in-cylinder temperatures
Compression can be increased by performing any one of the following modifications:
a) reducing combustion chamber volume (i.e.: domed pistons, smaller chamber heads, mill ing heads, etc.)
b) adding forced induction (Nitrous, Turbocharging or Supercharging)
c) camshaft change
As compression increases, a colder heat range plug, higher fuel octane, and careful attention to igni-tion timing and air/fuel ratios are necessary. Failure to select a colder spark plug can lead to spark plug/engine damage
Advancing Ignition Timing
Advancing ignition timing by 10° causes tip temperature to increase by approx. 70°-100° C
Engine Speed and Load
Increases in firing-end temperature are proportional to engine speed and load. When traveling at a consistent high rate of speed, or carrying/pushing very heavy loads, a colder heat range spark plug should be installed
Ambient Air Temperature
As air temperature falls, air density/air volume becomes greater, resulting in leaner air/fuel mixtures.
This creates higher cylinder pressures/temperatures and causes an increase in the spark plug's tip temperature. So, fuel delivery should be increased.
As temperature increases, air density decreases, as does intake volume, and fuel delivery should be decreased
Humidity
As humidity increases, air intake volume decreases
Result is lower combustion pressures and temperatures, causing a decrease in the spark plug's tem-perature and a reduction in available power.
Air/fuel mixture should be leaner, depending upon ambient temperature.
Barometric Pressure/Altitude
Also affects the spark plug's tip temperature
The higher the altitude, the lower cylinder pressure becomes. As the cylinder temperature de-creases, so does the plug tip temperature
Many mechanics attempt to "chase" tuning by changing spark plug heat ranges
The real answer is to adjust jetting or air/fuel mixtures in an effort to put more air back into the en-gine
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Also someone pointed out this websites quotes (I'd bet these guys are pretty bogus after looking at the products they sell):
"There are two ways to control NOx production from today’s vehicles: Pre-combustion and post-combustion. Pre-combustion NOx control is the primary method of reducing NOx emissions. Simply stated, it is necessary to keep combustion temperatures low. Methods of doing this include lowering compression, retarding timing, enriching the fuel mixture and EGR flow. Post-combustion NOx control occurs in the catalytic converter."
Larry (or anyone else), would you have any analogy I could show my customers that puts it in semi plain english, lots of them are still confused when I tell them that higher octane fuel on it's own will not make more power..lol
Thanks again, I'm so glad I found this site.
