We've all seen the marketing campaigns from spark plug manufacturers extolling the virtues of the latest and greatest plug design. One of the more notable developments in plug design that has been fruitful is the use of precious metal alloys for center electrodes. High melting point alloys such as platinum and iridium have enabled longer plug life in engines that are designed to run extremely lean mixtures, or in some high performance applications where combustion pressures and temperatures are extremely high due to turbo charging, supercharging, and/or nitrous oxide injection.

As I touched upon in my previous article titled "Getting a Better Spark", most modern production-based ignition systems are designed to provide a relatively weak spark over a fairly long duration. Regardless of the design of the particular ignition system, the spark plug's function is to ignite the air and fuel mixture in the combustion chamber. When the voltage delivered to the plug by the ignition system becomes sufficient to reach the ionization point of the fuel mixture in the combustion chamber, the current will ark across the plug gap to ground. The spark serves to ignite the mixture and create a flame front that rapidly disperses throughout the chamber as the combusting fuel and air mixture expands.

In modern engines running extremely lean mixtures, having relatively long spark duration is an engineering solution used to meet the ever more stringent clean air standards. These types of systems are also used to prevent rpm surge that can occur in some lean-burn fuel injected engines run at steady throttle. Conveniently enough, the use of such relatively low energy ignition systems is also due to cost considerations. The swirling mixture of air, with fewer fuel molecules available presents a mixture that is harder to ignite. Since the air and fuel mixture itself tends to provide a certain level of evaporative cooling to the combustion chamber, these leaner running engines tend to run higher combustion temperatures. In such applications, the higher thermal stress on the plug created the need for precious metal/high melting point electrodes such as platinum and iridium.

From a performance standpoint, plug manufacturers have tried to develop variations to long-standing designs in attempts to ignite the fuel and air mixtures more efficiently. Efforts have primarily focused on the center electrode and ground construction. Plug manufacturers have long ago realized that plug design is not a “one size fits all deal”. Today, plugs are purpose built, high quality products that can have a significant effect on an engine's performance. Many racing plugs, for example, will usually have a silver center electrode along with a shorter ground tang. This configuration allows more spark to be exposed to the incoming mixture as the spark is less obscured by the tang itself. For many years, tuners have indexed plugs by shimming them so that the gap would face towards the center of the cylinder or intake port; the theory behind this being that the flame front would ignite and move more rapidly throughout the chamber. In addition, racing spark plugs are not usually fitted with a resistor, and as mentioned, often utilize a silver center electrode. Remembering from last month's article, the use of silver in most performance applications is due to its superior electrical and thermal conductivity, enabling higher spark energy and rapid heat dissipation. Regardless of the design details of the particular spark plug, there are four main factors when choosing a plug for a particular application.

For most people the easiest way to ensure they're using the correct spark plug for a given application is to consult their owner's manual and/or their service provider. There are many of us however, that are driven by a desire to seek improvements in performance and/or fuel economy. We at Team Motorcyclist's Post have looked at some alternative spark plug designs from various manufacturers, and have found some that work better for our applications than others.

One company that has some very unique designs of performance spark plugs is Brisk. We came across this company and their products at the recent Performance Racing Industry Show in Indy. The European based company offers their Brisk Premium Spark Plugs that we have tried with some measure of success in our race motors. A new name to the U.S. market, Brisk USA is set to take on some of the world's largest spark plug manufacturers head to head. No small player themselves, Brisk is one of the largest suppliers of spark plugs in Europe. While offering high quality conventional style plugs for a wide variety of applications, Brisk also manufactures some interesting designs that I'll mention in reference to the accompanying illustrations.

While we have elected not to publish specific horsepower/torque gains from using these plugs in our race motors, I will say that we were pleasantly surprised by the results. Moreover, overall throttle response was improved over the plugs we have previously used. It's not that often that you can find noticeable improvements without significant investments in time and money.

Brisk currently offers several variations of retracted ground electrode plugs. Brisk Premium LGS Series plugs are noticeably different than conventional plugs in that there is not a typical ground tang. In these designs, the grounding mechanism is incorporated into the specially formed plug body. While there are several major plug manufacturers that make variations on this style, Brisk offers what I feel are the most unique and the smoothest flowing (I'm talking cylinder head gas flow here).

Brisk Premium ZC/ZS/TXS Series plugs go yet another step in a very unique design direction. Brisk has incorporated two "ground rings" built into the insulator tip portion of the plug; this is the porcelain part that protrudes from the plug barrel. In developing these plugs, Brisk has what they claim to be the worlds only plug that provides three simultaneous sparks per one ignition impulse. Brisk informed me that these plugs were originally developed in conjunction with BMW's efforts to solve steady-throttle surging problems in some of their motorcycles, notably their flat twins.

Note: BMW now uses a revised ignition system/plug arrangement that has two plugs per cylinder firing at slightly different intervals; this eliminates the problem while aiding efforts related to increased performance and emissions compliance.

Brisk states that some of these types of plugs may require more ignition system spark energy than a conventional plug, and therefore may not be appropriate for some applications without an ignition system upgrade.

Brisk offers some material and/or style variations of these plugs depending on what the particular application is. The company states that the general advantages include:

A European magazine called BMW Moto recently conducted an independent test that compared the performance of several brands of retracted ground style plugs. The tests were run on one of the latest BMW flat twins using various plugs from Brisk and other manufacturers. The results of these tests showed that in this application, the Brisk plugs made measurably more power and torque of the plugs tested. Brisk states that in other tests performed on cars, measurable improvements in horsepower, torque, and even fuel economy has been discovered due to apparent improved combustion efficiency offered by their designs.

For those who are looking for performance enhancements, your spark plugs may be something you should look at, especially if you've been meaning to change them out anyways. While your particular application may not be able to support the use of some of the most advanced features I've discussed here, Brisk can likely offer you a suitable replacement in a high quality product. While street applications normally require no tuning changes, note that all-out performance applications may require some experimentation with ignition timing and jetting to achieve optimal results.

Brisk USA carries a complete line of high quality spark plugs for most applications. For more information, you can visit their website at www.briskusa.com, or call Martin Uhlir at 713-459-6977.

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