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The picture below has correct heat
range , but is also the leanest that will make best HP . It
has a full-turn of very light soot color on the base ring and heat range
mark is half way up on ground electrode strap .
Most engines can't run this lean and make their best power curve, but
engines that are highly efficient, without any dead areas or fuel air
separation spots in cylinder heads , will like to run this lean
.
The spark plug picture below ...
shows the "Richest" a spark plug can be and make good Horsepower and
Torque curve , any richer than this will definetly hurt Peak
Horsepower mainly, but not so bad for peak Torque .
The spark plug picture below ...
shows a "Too Rich" spark plug . Horsepower and
Torque will definetly start to be reduced .
In all the above photos of spark
plugs you will notice that the white porcelain looks the same color
. The white porcelain does not indicate jetting
!! Do not look at the porcelain insulator for jet
changes ... instead look at the plug's base ring , the last thread
ring that has the ground strap welded to it .
How to read spark plugs
;
*** Mostly valid
only for full-load dyno tests ,
or if engine is quickly turned-off
after
finish line, and then towed back to pits,
and spark plugs
removed for readings there !
Plugs, best viewed with a 10x power
illuminated mag. glass
Heat
Range = Ground Strap , the ground strap indicates the
heat-range of
the spark plug. If the "color" of
the ground strap "changes" too-close
to the ground-strap's
end, (which is above the center electrode), then
the
heat-range is "too-cold" , meaning that the strap is
loosing
heat too-quickly to the base-ring, and is not
able to burn-off
deposits until near its end.
If the "color" of the strap changes near
where it is
welded/attached to the base-ring(last thread ring),
then
it means that the plug heat-range is "too-hot",
because heat is not
being tranferred/cooled from the
strap to the base-ring quickly enough
!!!! The strap
might begin to act like a "glow-plug",
eventually
causing preignition/and/or detonation later on.
Proper
heat-range is when the "color" is at the
half-way point on the strap,
neither too-cold or
too-hot.
(Color= meaning the evidence
of heat/or lack of heat
by the appearance dark vs lightened color of
metal)
Jetting = the air/fuel mixture ratio shows up
on
the base-ring (the last thread ring, it has the strap
welded to
it).
You want 1 full-turn of light-soot color on the base
ring!!!
If you want to tune for max. power, then you
want 3/4 to 7/8ths of a
full-turn of light soot color
to show-up on the base-ring, but this is
on ragged-edge
of being too-lean, but will make the most HP on most
engines. To be safe, leave it at a full turn of light
soot color.If
the base-ring has a full-turn of color,
but there are "spots" of heavy
build-up of "dry-soot"
on top of color, then jetting is too-rich .
NOTE> If the base-ring has a full turn of color with
some
spots of heavy dry-soot, then jetting is too-rich,
REGARDLESS,if
porcelain maybe "BONE-WHITE", jetting is
still TOO-RICH
!!!
NOTE> Do not look at the porcelain to read jetting !!!
Porcelain = the porcelain shows up
preignition/detonation,
it will not accurately reveal jetting/air/fuel
ratios.
To look for the first/beginning signs of detonation,
search
the white porcelain for tiny black specks or
shiny specks of aluminum
that have fused to the porcelain.
When detonation occurs, part of the
air/fuel mixture
explodes instead of burning, the explosion is heard as
a
"metallic-knock", this audible knock is the result of a
sound
shock-wave, this shock wave travels back and forth
across the clearance
volume "disrupting" the cooler
boundary layer gases that cover the
entire clearance volume
area,this disruption allows "more" heat to be
transferred
into parts, especially, domes/piston tops,...along with
the
very rapid rise in pressure like a hammer like blow, pistons
can
get torched/melted sides/holes !!! With the early signs
of detonation,
the shock-wave will also rattle rings causing
the tiny amounts of oil
that now gets by rings, to be fused
to the white porcelain as tiny
black specks, also fused as specks
are soot that was clinging to
clearance volume surfaces
in the relatively "still-air" of the boundary
layer.
One step beyond the black specks,will be tiny
specks/balls
of alumimum coming off-pistons that will be fused to
white
porcelain,....the next step to be reached is occasional
pieces
of the porcelain being broken-off as detonation gets
worse,ETC.
Soon after that, are holes, blown head gaskets,
broken
connecting rods, ETC.
NOTE> additional signs of
beginning detonation are piston
rings. By comparing ring's
"free-diameter" to "out-of-box"
free-diameters of new unused rings
will reveals beginnings
of detonation before much harm is caused !!!
This is a result
of the above previous explanation about heat being
transferred
more readily because the of the relatively
insulating/cooler
boundary layer being disrupted by the
shock-wave.
A piston ring is a simple spring,
when a spring is
over-heated it will loose tension.
Center Electrode = the
very tiny sharply defined porcelain -"ditch"
that encircles the center
electrode, will also showup early
signs of preignition/detonation/wrong
heat-range. Look for signs
of the ditch beginning to be filled up with
melted porcelain,
you will need a 5x or 10x mag. glass.
The
"Ground-Strap" = Heat Range
The "Plug's Base-Ring" =
Jetting
The "Porcelain" = signs of preignition/detonation
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