Unless your engine's ignition system is properly designed and maintained, there's a good chance that you are losing out on horsepower and wasting fuel. Since all gasoline engines depend on a spark to start the combustion cycle, a misfire (when the spark fails to fire completely) or a spark that is not of the proper intensity or duration will prevent your engine from realizing its peak power and efficiency. While every component in the ignition system is of equal importance, the spark plug wires, or spark plug cables are possibly the most overlooked. For this installment of the lab, we put six of the most popular ignition wires to the test against a set of used wires that would represent what is probably on your car. This session of "The Lab" will not only reveal how the wires perform on the dyno and on an ohmmeter, but we will also tell you how well the wires fit at the distributor cap and spark plug. While we lack the resources to test how long the wires will last or how much EFI and RFI is generated by the wires, the information that we are able to supply should be useful information in helping you determine which wire sets are right for you. When the results are reviewed, we believe that you will be convinced that high-quality, aftermarket spark plug wires are a wise investment.

Ignition Basics
The purpose of an automotive ignition system is to produce a powerful enough spark to initiate combustion of the air/fuel mixture. Ideally, the ultimate ignition system would cause all of the air/fuel mixture to be ignited all of the time. Additionally, it would be ignited at the precise time when the maximum amount of combustion pressure could be turned into horsepower. Quite simply, the ignition system needs to be effective, consistent and precise. When an ignition system is upgraded and performance is closer to this ideal, many benefits will be realized. Combustion is more complete, misfires are reduced and the engine is able to extract more power from each drop of fuel. Thus, power increases and mileage improves.

The Ignition System
Modern automotive ignition systems fall into two categories, distributor-based and Distributorless Ignition Systems (DIS). Recently, some manufacturers have begun incorporating coil-on-plug ignition systems (a variant of DIS systems) that don't use spark plug wires. However, the vast majority of all ignition systems regardless of type rely on spark plug wires to deliver the spark energy from the coil to the plug.

The Physics

Voltage Requirements
Let's look at the factors which influence how much voltage is needed for a spark to occur at the spark plug. After all, if voltage requirements at the spark plug gap exceed the voltage capabilities of the ignition system, no spark will occur at all. There are basically four factors which influence the voltage requirements at the spark plug: spark plug gap, cylinder pressure, temperature, and air/fuel ratio. When spark plug gap is increased, the voltage required to jump the gap is also increased. Years ago, the typical breaker-point ignition system would use a .030- to .035-inch gap. Today, the majority of electronic ignition systems are designed to use a spark plug gap between .044 and .055 inches. Of course there are exceptions to the rule, as supercharged or turbocharged vehicles will use smaller gaps. On turbo, supercharged, nitrous, or high-compression applications, the cylinder pressure when ignition takes place is much higher than a low-compression, normally-aspirated engine. As a result of this higher pressure and higher temperatures, more voltage is required to bridge the gap. Today's leaner running engines also put more of a demand on the ignition system. As air/fuel ratios become fuel lean, the voltage requirements also increase. As it is easy to see, an effective ignition system must be able to meet the voltage requirements needed to cause a spark at the plug. Unfortunately, having the spark occur is just half of the story-the spark also needs to be powerful enough to ignite the air/fuel mixture.

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