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Spark, the sequel
Posted by GOrilla on Mon Oct 12 20:01:56 1998:
In reply to: Re: Replacing Spark Plugs?? posted by The Man In Black on Mon Oct 12
Spark, the sequel.
The purpose of the ignition wires is to conduct the maximum coil output energy to the
spark plugs with a minimum amount of radiated electromagnetic interference (EMI) and
radio frequency interference (RFI).
On most street applications using digital computers for engine management control,
excessive EMI and even RFI can interfere with ECUs and cause running problems. With
the Valk EMI and RFI is not a problem unless your running radio, stereo or radar detector
There are 3 basic types of conductors used in automotive applications:
Carbon string, solid and spiral wound. Most production engines come equipped with
carbon string or spiral wound. The solid core types are used exclusively for racing, mainly
with carbureted engines because they offer no EMI or RFI suppression. They generally
have a low resistance stainless steel conductor. These types are rapidly losing favor,
even in racing circles.
The carbon string type is the most common and work just fine in most stock type
applications. The conductor is usually a carbon impregnated fiberglass multistrand.
Suppression qualities are fine with resistances in the 5K to 10K ohms per foot. They are
cheap and reliable for 2 to 5 years usually, then they may start to break down and should
be replaced. High voltage racing ignitions will likely hasten their demise.
The spiral wound type is probably the best type for any application. The better brands
offer excellent suppression, relatively low resistance and don't really wear out.
Construction quality and choice of material vary widely between brands.
Some amount of resistance is required along with proper construction to achieve high
suppression levels. Resistance is also important to avoid damaging some types of coils
and amplifiers due to flyback (high voltage transformer) and coil harmonics. Beware of
wires claiming to have very low resistance. These CANNOT have good suppression
Beware of any wires claiming to increase hp. Ignition wires CANNOT increase hp. As
long as the wires that you have are allowing the spark to jump the gap properly, installing
a set of $400 wires is strictly a waste of money. Lately, some truly "magic" wires have
come onto the market claiming to not only increase power but also to shorten the spark
duration from milliseconds to nanoseconds. Spark duration is determined primarily by coil
inductance and coil resistance so these wires CANNOT shorten the spark duration by the
amount claimed. The wire resistance has a minimal effect on discharge time because of the
high voltage involved. A very short duration of spark is in fact detrimental to ignition
because of lower probability. Yes, every fire is a crap shoot, you try to install the right
products to increase your chances of consistant firing and spark.
These same wires claim to increase flame front propagation rates and the ability to ignite
over- rich mixtures for more power. In my experience and readings I have seen that once
ignited, the mixture undergoes the flagregation process and that the progression rate of
the flame front is totally independent of the spark. Also, I have learned above that most
gasolines will not ignite nor burn at air fuel ratios richer than 11 to 1, period, and that
maximum power is actually achieved at around 12 to 1 AFR.
Wires that use a braided metal shield over the main conductor which is grounded to the
chassis offers poor suppression because it does not cover the entire conductor. Any
energy leaking out of the main conductor by induction is actually wasted to ground and
will not make it to the spark plug. These wires also have very low resistance which can
have a detrimental effect on coils and ignition amplifiers due to severe flyback effects
which are normally damped by circuit resistance.
Other claims for these wires include current flows of up to 1000 amps. The current flow in
the ignition circuit is determined by the coil construction and drive circuits, not by the
ignition wires. Most ignition systems are current limited to between 5 and 15 amps. The
most powerful race systems rarely exceed 30 amps. To flow current at 1000 amps, you
would require #0 welding cable for the ignition system! GO figure :)
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