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Spark Plugs and Spark Plug
Wires
WARNING:
Use
only resistor core spark plug wires with all Power Arc
Ignitions. See spark plug wire section below.
Use resistor spark plugs with all electronic ignitions to limit
the conducted EMI noise and radiated RFI noise..
Initial suggested settings for spark plug gaps are:
Single plug 0.028-0.032"
Dual plug 0.025-0.030"
These are maximum settings, go down from here
Spark plug
gap should be made as small as possible, while still maintaining
performance. A wide spark plug gap can cause hard cold starting,
misfires during rich or lean fuel conditions, and reduction of
upper rpm range. To maintain a good secondary spark (multiple
spark) within a wider rpm range it is wise to run a narrower
spark plug gap. It is better to precisely place two stable,
consistent sparks than to fire one wider spark that may cause
misfires under various conditions.
Many
things effect spark plug gap settings
Compression
Ratio: The higher the engine compression, the more voltage
required to fire the plug, and the narrower the plug gap should
be.
RPM: The higher
the rpm's the less time the coil has to charge to break over
voltage or complete saturation. A narrower spark plug gap will
help high rpm stability.
Spark plugs with
large side electrodes (ground straps) or spark plugs with split
side electrodes are not recommended, they interfere with the
flame front at the point of ignition.
Coil choice, fuel flow, intake velocities & fuel temperature
are but a few additional factors that can effect spark plug gap.
Spark Plug Choice
In
most cases, it is not until the engine is modified, or the
compression is raised significantly, that stock ignition systems
and spark plugs begin to show signs of being inadequate. At this
point, a variety of factors determine which spark plug will be
best suited for a particular configuration. In these modified
engines, specific electrode/tip combinations, electrode
materials and colder heat ranges can provide measurable gains in
power. If your vehicle has had extensive modifications, it would
be best to seek the advice of the manufacturer of your vehicle,
the aftermarket supplier who manufactured your modifications, or
your mechanic.
Modifications
that will typically not require specialized plugs (in most cases
the factory installed plug will be more than adequate) include
adding a free-flowing air filter, headers, mufflers and rear-end
gears. Basically, any modification that does not alter the
overall compression ratio will not usually necessitate changing
plug types or heat ranges. Such minor modifications will not
significantly increase the amount of heat in the combustion
chamber, hence, a plug change is probably not warranted.
However,
when compression is raised, along with the added power comes
added heat. Since spark plugs must remove heat and a modified
engine makes more heat, the spark plug must remove more heat. A
colder heat range spark plug must be selected and plug
gaps should be reduced
to ensure proper ignitability in this
denser air/fuel mixture.
Frequently
Asked Questions
Q: Why
should I use a resistor spark plugs & spark plug wires?
A:
"R" or resistor spark plugs use a 5k ohm ceramic
resistor in the spark plug to suppress ignition noise generated
during sparking.
You must use
resistor spark plugs & wires in any vehicle that uses
electronic ignitions or on-board computer systems to monitor or
control engine performance. This is because resistor spark plugs
& wires reduce (EMI) electromagnetic interference with
on-board electronics.
They are also
recommended on any vehicle that has other on-board electronic
systems such as engine-management computers, two-way radios, GPS
systems, or whenever recommended by the manufacturer.
In fact, using a
non-resistor plug or low resistance spiral wound spark plug wire
in most applications may actually cause the engine to suffer
undesirable side effects such as an erratic idle, high-rpm
misfire, engine run-on, power drop off at certain rpm levels,
abnormal combustion and probable damage to the ignition and/or
ignition coil.
Q: Why are
there different heat ranges?
A: It is a
common misconception that spark plugs create heat. They don't. A
heat range refers to how much heat a spark plug is capable of
removing from the combustion chamber.
Selecting a spark
plug with the proper heat range will insure that the tip will
maintain a temperature high enough to prevent fouling yet be
cool enough to prevent pre-ignition. While there are many things
that can cause pre-ignition, selecting a spark plug in the
proper heat range will ensure that the spark plug itself is not
a hot spot source.
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