I found this on a FAQ board today and found it very eye opening!
Mitch
> I have heard that platinum plugs aren't very good for performance...how is
this so?
All things being equal, a more powerful spark will create higher cylinder
pressure which will create more power. The power of a spark is determined by
its voltage (more voltage = more powerful spark).
Aside from variables such as cylinder pressure and A/F ratio, the amount of
voltage required to jump across the gap of a given type of spark plug is
determined by the plug gap. A smaller plug gap requires less voltage to jump
across the gap and a larger plug gap requires more voltage to jump across
the gap.
There is a way to reduce the amount of voltage required to jump across the
gap of a plug. By increasing the number of sharp edges that the spark can
jump from and to (as in SplitFire and Torquemaster plugs) or by using an
electrode material that is a more efficient conductor than the standard
steel material (like platinum) you can decrease the amount of voltage
required to "jump the gap". The only problem is that these "specialty" plugs
will produce a less powerful spark than a standard plug will at the same
gap. This means that, as long as your ignition system can provide enough
voltage to jump the gap on the spark plug all of the time, with these
"specialty" plugs installed in your car your engine will produce less power
than it will with standard spark plugs. The only way you can regain the
power lost with these "specialty" plugs is to open their gap out farther (a
wider gap requires more voltage to jump the gap).
I've seen a number of cases where people have installed SplitFire,
Torquemaster or platinum plugs in their car in the place of standard spark
plugs and have complained of reduced power. In all of these cases the
specialty plugs were installed using the plug gap specified for the car's
original standard plugs (with the exception of the Torquemaster, whose gap
is not adjustable). The reduced spark power due to the reduced voltage
requirement of these plugs was the culprit.
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