In The Beginning

Probably the most efficient transfer of spark energy is made with solid core spark plug wire. This type of wire was extensively used prior to the 60's before the introduction of car radios as standard equipment. A few modern day exceptions exist such as certain race applications and a few European car manufacturers. The problem with solid core wire is that it emits large amounts of RFI ( radio frequency interference) which affects radios, and onboard electronic systems in cars. When current passes through a wire, a magnetic field is formed. If the current flow is switched on and off rapidly as with an ignition system, RFI is caused by the magnetic field collapse (some refer to it as EMF which stands for electromotive force). When manufacturers started installing radios in cars, a solution was needed to reduce the RFI. One of the first solutions was to mount resistors on the wire ends to reduce the current flow and consequently reduce the EMF and resultant RFI. The second solution, and the most popular by far, was to make the whole wire a resistor. Thus the age of carbon core wire (sometimes referred to as graphite core) was born. This type of wire needed a whole new type of construction over conventional solid core wire. Carbon core wire's basic construction starts with a non conductive structural member (nylon or Kevlar™) over which carbon fibers are deposited. These carbon fibers are typically blended with latex or silicone to form a flexible coating. A layer of EPDM rubber is then deposited over the core as primary insulation. Next a nylon bonding weave is placed over the wire which is followed by a final coating of either EPDM or silicone rubber. When new, this wire performs as designed. Over time however, with heat and vibration the carbon fibers tend to loosen which degrades conduction and eventually requires replacement. For this reason some OEMs (original equipment manufacturers) recommend replacement every 3 years or 60,000 KM. Carbon core wire is quite economical for manufacturers to use while suppressing sufficient RFI. This wire typically has a resistance of 3,000 to 20,000 ohms /ft. depending on the manufacturer.

O.K. So Where Do We Go Now ?

Previously mentioned, RFI is reduced by limiting the current flow in the wire. This reduction of current flow also results in a weaker spark to the plugs. An internal combustion engine operates on the principal of air and fuel burning in a cylinder and the expanding gases driving down the piston. That's right the fuel burns, not explodes as some believe. The hotter the spark in the cylinder the better the air/fuel ignition and better chance at complete combustion. We will come back to this in more detail later on, along with some common misconceptions. Since the hotter the spark the better combustion, an engine's efficiency improves, simple fact. Carbon core wire is not our most efficient choice here, and solid core wire can't be used on modern vehicles. So where do we go from here ? The newest technology is wire wound construction which can go under many names such as magnetic suppression wire ( mag wire ), spiral core, helical core and so on. Although this type of wire is more costly than carbon core, vehicle manufacturers are using this type of wire more and more in newer vehicles for better efficiency and longer life.