All Spark Plug Wire Is Not The Same

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There are four major types of spark plug wires but the only one safe to use with all street vehicles is carbon, high-resistance suppression wires.

All spark plug wire is not the same. There are Carbon Conductors, Low-Resistant Spiral Wound conductors, Solid Core conductors, and Capacitor Effect conductors to name the four main divisions of spark plug wire. Each type of spark plug wire functions differently and have different effects on EMI and FRI as well as the spark.

What Are Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI)?

If you are old enough to remember when AM radios were standard equipment on new cars, you may recall the problem of ignition noise. It sounded like the putt putting of an outboard motor emanating from the speaker in the dashboard. The pitch and volume increased with engine RPMs. That was RFI. That signal emanating from the spark plug wiring entered those old AM radios through the antenna as well as through the power wiring that acted as an antenna for those RFI signals. When FM radios became standard equipment, RFI became less of a problem.

Today, EMI is the problem that we need to be concerned with. The unvarnished truth is that EMI is just our old archenemy RFI with a new name, both are forms of unwanted electromagnetic waves that propagate from the spark plug wiring. These spurious signals are problem today because they send false signals to all the electronic control modules (ECMs) that manage engines, drive lines, and other vital systems on our cars. Those signals need to be suppressed.

Carbon, High-Resistance Ignition Wire Suppresses EMI and RFI.

Carbon Suppression conductors are used as Original Equipment Manufacturer (OEM) wiring by new car manufacturers. Carbon suppression wire also represents the principal sales in replacement wire sets. Besides suppressing EMI and RFI, carbon core wire has one other key advantage; it is cheap to manufacture. Suppression wire consists of a fiberglass, Kevlar, or combination fiberglass/Kevlar substrate over which a high-resistant coating of silicone or latex is applied. The high-resistance reduces the spark current, and that is what reduces the EMI. That seems to be the way it always is you have to give up something to get something.

Solid Core Spark Plug Wires

These wires consist of a solid copper, tin-plated copper, or aluminum wire core. Solid-core wires are still used in some carburetor-equipped racecars, but they should not be used on your day to day vehicles. They should not be used on fuel injected engines, engines with electronic ignition systems, or on vehicles with ECMs. The EMI propagated from unsuppressed spark plug wires can cause irreparable damage to ECMs and other on board electronics. Solid core wire can be suppressed by placing a spark current reducing resistor at each end of the wire. Spark current reducing resistors are another potential source for future problems. Replace carbon core suppression wire with carbon suppression wire. As the adage goes, "If it is not broke, do not fix it."

Low-Resistance Spiral wound spark plug wire

Spiral wound spark plug wire is an after-market product touted as high-performance spark plug wire. Noting could be further from the truth. When it comes to spark plug wiring used with today's electronic ignition systems, low-resistance does not equate higher performance. Spark current generated in high energy electronic ignition systems is not Direct Current (DC) as the current supplied by a battery, but a high frequency pulsating current with alternating current (AC) characteristics. Pure DC uses the entire cross-sectional area of a conductor. High-frequency current does not use the entire cross-sectional area of a conductor but flows over the surface of the conductors. The varying electromagnetic field forces the current flow to the surface of the wire, this is known as the "Skin Effect." I am not going to get into the how and why of Skin Effect here because you do not need to understand this electric theory. What you need to know is that low-resistance spiral wound wire use less wire which translates to less surface area for the current to flow on. This high-performance wire actually, in most cases, reduces performance.

Capacitor Effect Wiring

This is spark plug wire with a grounded metal braid around it. This grounded metal braid acts as one plate of a capacitor with the wire insulation acting as the capacitor dielectic. You will hear all kinds of claims about how this wiring will improve performance. Do not listen to those claims. The wiring can do serious harm to on board computers.

The best advice that I can give you is to use the same kind of spark plug wires that the engineers who designed your car used. Do not experiment with other wires, experimenting could lead to expensive repairs.


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