The purpose of the ignition wire is to deliver all of the energy that the ignition system can produce from the coil(s) to the spark plug. An ignition wire can't, in and of itself produce additional energy. It is merely the conduit for the energy already produced. The difficulty in delivering all of the energy under all conditions without causing problems due to Radio Frequency Interference (RFI) and Electro-mechanical Interference (EMI), is what differentiates one type or brand of ignition wire from another. The electrical property that primarily affects this is resistance. In this case it is the resistance to the flow of electrons (electricity) and is measured in ohms. When you hear or read of an ignition wire with 50 ohms of resistance it means 50 ohms per foot. The perfect ignition wire would have zero ohms resistance and zero RFI. The problem in producing the perfect wire is that resistance is inversely proportional to RFI. That is as you lower the resistance toward zero, it produces more RFI. The ideal situation is to have the lowest resistance wire while keeping RFI below levels that would cause problems with computerized engine controls (SAE has specifications for this) and without violating FCC regulations. We will now explain the various constructions of ignition wire to help you make an informed decision for your particular application.

Conductors

There are three basic designs of ignition conductor with variations of each. This will describe each of the conductors and provide an understanding of how each will function in a particular application.

Copper: The very first ignition conductors were made of copper and were used exclusively for almost sixty years. At the time they were the ideal choice because they had almost no resistance to the flow of electricity and the conductor would last beyond the life of the engine. Then in the 1960's the Federal Communications Commission (FCC) issued regulations that limited the amount of RFI that could emanate from a source, mainly the automobile. The older generation may remember "hearing" a cars engine over their radios and televisions. The copper conductors gave off far too much RFI to be compatible with a world that was becoming "wireless" with its communication devices. For these reasons copper is rarely used on automotive or marine engines. The exception to this is a few European car manufacturers that use the copper conductor but install a resistor, usually 5000 ohms, at the spark plug boot. Copper was an excellent choice years ago but, for the most part, is no longer the best choice.

Carbon: Today the most widely used conductor is carbon-impregnated latex which is applied over Kevlar® or fiberglass. It is often referred to as "suppression" conductor because of its RFI suppression properties. It is used by virtually all of the original equipment and aftermarket wire set producers. This conductor has two distinct advantages; it has excellent RFI suppression and is relatively inexpensive. However as in most things, there is a downside. The carbon conductor relies on microscopic carbon particles touching each other in order to efficiently conduct electricity. Any movement of the wire, whether through handling or engine vibration, causes the carbon particles to move apart. When they do, the flow of electrons through the particles causes them to polarize and act like little magnets. As we learned in grade school, opposites attract and like charges repel. The carbon particles that "face" each other with the same charge (positive or negative) "push" each other apart causing a breakdown in the flow of the electrons. When enough of them react like this the wire breaks down, that is, the electrons stop flowing or they find a shorter path to ground - usually the engine block. When this happens the engine misfires.

Another issue with carbon wires is the effect its "good" property, resistance, has on the insulation encasing the conductor. As the resistance increases, some of the energy being "used" is converted from electrical energy to heat energy. (The reason a light bulb gets hot is because the filament is a resistor that converts the electrical energy to light and heat .) When enough of this internally generated heat combines with the external heat from the engine compartment, it can lead to the premature failure of the insulation, which lets the spark jump to the nearest ground instead of across the spark plug gap. It may even lead to a burn out of the conductor itself, particularly where it is folded back to attach to the terminal at the spark plug end of the wire. There are carbon conductors made with a thin extrusion of silicon over them to help alleviate this problem however they are more expensive. The additional expense eliminates most of the price benefit of the carbon conductor.

Due to the above issues a carbon conductor begins to deteriorate from the first moment that it conducts electricity. The initial resistance is from 3000 ohms to 7000 ohms per foot. This gradually increases until it fails. Failure normally takes place between 15,000 and 50,000 miles. Carbon conductor is a good choice when price is a primary concern. It will perform very well in most applications. It is not a good choice if consistent performance or longevity is an issue.

Wire Wound: Often referred to as "Magwire" or spiral wound, wire wound conductors have a carbon core conductor that is wound with a thin thread of a metal wire, usually stainless steel or a copper-nickel alloy. This gives it the low resistance advantage of the copper conductor but also give it the RFI suppression advantage of the copper conductor. Wire wound, unlike carbon conductor, is not affected by internal heat and its resistance remains constant instead of gradually getting higher. Wire wound conductors generally have a resistance range from 350 to 1500 ohms per foot. With the advent of OBDII having the engine's computer record minor misfires and with car manufacturers trying to meet the requirements of their emissions warranties, some original equipment manufacturers are switching form carbon core to wire wound.

In the past few years a new construction of wire wound conductor was developed. The "reactive" wire wound conductor has ferrite-impregnated latex instead of the carbon center and is wound with a copper-nickel alloy instead of stainless steel. The "reactance" this creates allow us to get resistance as low as 25 ohms per foot while still suppressing the RFI.

As you can see from the last two paragraphs, wire wound is superior to the carbon conductor. The only disadvantage is price and the lower the resistance the higher the price. The regular wire wound conductor is about twice as expensive as the carbon conductor. The reactive wire wound conductor can be, depending on how low the resistance is, ten times as expensive as the carbon conductor. In summation, the wire wound conductor is the best choice if longevity, consistency and low resistance outweigh the price advantage of carbon core.

Other Factors Affecting Conductors: Electromagnetic Interference (EMI) is similar to RFI in the problems it causes however it acts differently. EMI is produced by the flow of electrons through a conductor creating a magnetic field. This field actually extends outside of the insulation of the wire. Unlike RFI, which can affect devices hundreds of feet away, EMI only affects devices in close proximity to the wire. This causes problems if the wires are routed too close to a sensor or the ECM. It will also cause a problem when the ignition wires are run for a long distance in parallel. The EMI can actually induce current flow in the wire running alongside it thereby creating a misfire. It is important to either closely follow the original routing of the wires or check or be sure they "cross" if two wires are running together for more than a foot or so.

Corona Effect : Corona Effect is a phenomenon which may be observed when viewing an engine running at night with the hood up. This phenomenon appears as a greenish blue halo around the wires. The amount of corona is dependent mainly on the humidity of the air and the amount of voltage pushing the electrons through the conductor. As the voltage and/or humidity increase, a more pronounced corona is observed. Be aware that it does not cause any problems. It is normal and there is absolutely nothing wrong with the wires. An actual arcing of a spark to ground does indicate a problem. A spark going to ground will make a noise, corona does not make noise.

There are seven materials commonly used for ignition wire jacketing. Please see the ensuing chart for a comparison of the materials:

The compounds in the chart are ranked from best to worst for ignition wire applications with Silicone being the best. The two most important factors in the chart are Heat Resistance and Insulating Properties. At the bottom end, PVC should never be used for ignition wire but some extruders use it for a very low cost ignition wire. It is "plastic" and can melt at temperatures as low as 130 degrees. In a double extruded ignition wire, the above are also used as the "first pass" insulation over the conductor. For the best ignition wire set, without regard to price, always look for dual silicone jackets - especially in a high heat condition.

Ignition Wire Compound Comparison

Ignition Terminals

Types: Ignition terminals come in various styles and materials. Terminals that attach to the spark plug or the SAE style (male stud) of the distributor cap or coil are either non-snap or snap lock terminals. There is no question that only snap lock terminals should be used. Non-snap lock terminals do not lock onto the plug securely and can even cause Radio Frequency Interference. The difference in cost is about a penny per terminal, certainly not enough to compensate for the possible problems they can cause. While it is obvious that a snap lock terminal should be used, it gets more complicated when we look at the different types of snap lock terminals. Probably more than 90 percent of all snap lock terminals are made of zinc plated steel. Zinc plating is perfectly acceptable for most applications. If, however, there is any possibility of extended exposure to salt air, there could be problems. Zinc is even used as a sacrificial anode on boats because the salt will eat away at the zinc and leave other metals relatively untouched. Fortunately stainless steel terminals are available from a few high quality terminal manufacturers like ETCO of Bradenton, Florida. Certainly all marine craft used in or near salt water and all vehicles kept in coastal areas should have stainless steel terminals. Unfortunately, almost no marine engine manufacturer other than Pleasurecraft/Crusader and Marine Power uses stainless terminals. There are two after-market marine wire set manufacturers that use stainless terminals and they are branded under Marine and Aqua Power. One other condition, often ignored, where stainless steel terminals are needed is in States that use road salt to melt ice. Once again, we haven't found many OE car manufacturers using stainless terminals. One company that uses only stainless terminals in their high performance wire sets is Vitek Performance in Atlanta , GA.

Spark Plug Boots

Types: There are two primary types of spark plug boots; the one-piece boot, and the three-piece boot assembly usually found on overhead cam engines. Since the greatest amount of heat that the ignition wire set has to contend with is usually at the spark plug, a material that will withstand temperatures in excess of about 340 degrees F is necessary. We recommend that all spark plug boots be made of silicone to avoid any problems. EPDM is an acceptable substitute in many applications where cost is a factor. The three-piece boot assembly consists of a top boot, phenolic tube, and a tip seal. It is important that quality phenolic tubes are used as they can have dielectric problems similar to those experienced by distributor caps and rotors. If there are any signs of carbon tracking on a set in use, it should be replaced. In addition, any wire set assembler should run batch tests requiring new phenolic tubes to pass a dielectric test in excess of 40,000 volts. We recommend that the top boot and tip seal be made of silicone.

Distributor / Coil Boots

Types: Distributor boots and coil boots are not subjected to the amount of heat that a spark plug boot is. For this reason, silicone is not needed at that end of the wire but they should be made of EPDM or a material with similar properties.

Dielectric Gel

A silicone dielectric (non-conductive) gel should be applied inside of the spark plug boot, preferably a silicone gel with Teflon added. This serves three purposes:

1. It helps seal the boot thereby preventing moisture from traveling onto the spark plugs ceramic insulator.
2. It lubricates the spark plug boot allowing for easier removal when necessary.
3. It "fills in" tiny spaces between the terminal and the spark plug connector helping to eliminate a possible source of RFI caused by terminal vibration.
   
   • The application of dielectric gel is so critical that Vitek voids the
     warranty on any set where the dielectric gel was not used.

Other Issues

There are a number of good quality wire sets on the market and many companies will have more than one level or quality of product. The high performance manufacturers tend to use better materials in the construction of their products than Original Equipment or some Aftermarket companies, however don't be fooled by some so called high performance wire sets that claim to improve performance by using multiple conductors (absolutely no benefit), metal shielding for a capacitive effect (we haven't been able to measure any benefit on test equipment with them), or anything else that sounds "gimmicky".

Summary

In order to help you with your choice, these are the facts and the very best ignition wire sets will have the following in common:

1. A low resistance wire wound (Magwire), reactive core conductor
2. A silicone outer jacket
3. Stainless Steel ignition terminals
4. Silicon spark plug boots

If the wire set you choose has all four of these features, you can be sure that you are purchasing a very high quality wire set that should perform well under extreme conditions. In addition, sets made with these materials should last indefinitely.

The Vitek Performance Solution

Vitek High Performance and Vitek Ultra Series ignition wires address all of these performance challenges. Vitek begins with an extremely durable multi-strand braided KevlarT core with a micro-wound stainless steel conductor and a highly conductive ferrite impregnated material for superior current characteristics. To maximize EMI/RFI suppression, Vitek High Performance ignition wires are encased in a pure, high temperature silicone jacket. That is where most wire manufactures end their construction. Vitek then applies a strengthening layer of braided fiberglass and an additional jacket of more pure silicone for the best suppression and durability in the marketplace. The Vitek Ultra Series ignition wires take ignition wire construction to the next level with an exclusive super high temperature resistant braided fiberglass jacket for the most extreme performance environments. Both series of wires are available in extremely low resistance racing configurations.

Our Original Equipment Series spark plug wires are a value priced solution that address the issues mentioned above as well. Manufactured with our unique stainless steel wire wound ("Mag Wire") conductor with a Dupont Kevlar Ò core for superior pull strength. The conductor is insulated with an extrusion of pure gold silicone then braided with fiberglass to achieve ultimate mechanical strength of the finished product. The wire goes through a second extrusion of pure silicone to a finished diameter of 6mm, 8mm, or 9mm depending on the original equipment requirements. The Series OE ignition wire is rated at 850 ohm per foot.