A spark plug is one of those internal combustion engine components often surrounded by sometimes confusing nomenclature tied in with plenty of hearsay and lack of understanding. Brisk USA is a name that some may not have heard before, but the company has been around for many years, building a wide variety of performance spark plugs. The focus of this story will be to break down many of the confusing terms into some simple facts that can lead you to make the right decision for your specific engine application.
Every spark plug manufacturer has its own set of numbers and letters which identify its product features and usage. This can seem complex until you understand how these letters and numbers are used. The best place to start may be to take a common application and break down each of the letters and numbers to explain what they mean. This will make it easier to understand how Brisk part numbers describe its line of spark plugs.
Spark Plug Basics
Before we break into that, let’s cover some generic spark plug designs that will help you understand the references. Let’s start with the spark plug main body configuration. The most common hex size for today’s engines is a 5/8-inch or 16mm socket size. The next important spec is the thread diameter. Thread diameter is the overall measurement of the width of the threads on a bolt, it is important to make sure you are using the correct thread diameter for the cylinder head to ensure the plug is installed properly. A 14mm thread diameter will not thread into a cylinder head that requires a 12mm thread diameter spark plug and vice versa.
The next critical measurement is thread pitch, which is normally a 1.25mm thread pitch on both 12mm (M12x1.25) and 14mm (M14x1.25) plugs for most popular performance engines. The only disparity with thread pitch is with 10mm diameter plugs which have 1.0mm thread pitch (M10x1.0).The next area deals with the type of sealing surface to the cylinder head, commonly referred to as the spark plug seat. The two most common types are tapered seat (conical) or one that uses a metal crush gasket called a gasket seat.
Another important specification when identifying the correct spark plug is the thread reach. The thread reach on a spark plug is defined as the length of the threads measured from the sealing portion of the plug body to the end of the threads. The thread reach numbers can vary widely based on the specific cylinder head in which the plugs will be used. This spec is critical because if the plug’s reach is too short, the business end of the spark plug — the center electrode and ground strap — will be retracted from the cylinder inside the cylinder head threads. This effectively shrouds the spark and does not allow the spark discharge of the spark plug good access to the air/fuel mixture. This absolutely kills power and efficiency.
A plug with excessive thread reach will push the threads too deeply into the combustion chamber, and in extreme cases, could actually impact the piston. Even if the plug does not hit the piston, exposed threads in the combustion chamber will create hot spots that can cause pre-ignition. This can cause serious internal damage such as broken pistons and cracked cylinder walls. We’ve seen it happen.
One example where improper application can cause issues regards the late ‘90s iron Vortec heads used on GM trucks and in many performance applications. The Vortec iron heads use a longer thread reach of 0.680 to 0.708-inch while earlier small-block iron heads employed a much shorter, tapered-seat plug with only a 0.430 to 0.460-inch reach. Using these earlier, shorter-reach plugs is an easy mistake that can easily cause issues with the engine’s operation and efficiency. This longer 0.708-inch thread-reach spark plug with the tapered seat is also common to the Gen-III/IV LS engines.
This leads us to the next topic of spark plug heat range. Once you have established the proper thread diameter, thread reach, and seat sealing type your engine requires, the heat range is the next important step. This is a good place to define what a spark plug’s heat range means. This refers to the plug’s ability to transfer heat from the white porcelain insulator to the cylinder head through the spark plug body.
All spark plug companies, including Brisk, assign a number to the plug to represent its heat range. With Brisk racing plugs, the heat range numbers run from cold to hot in ascending order. In other words, a number 10 plug is much colder than a number 17 plug. Not all companies use the same numbering convention, so it’s important to know when switching brands how each company’s heat range numbers are employed.
A cold plug provides a very short path for the heat to escape, keeping the center electrode and insulator nose cooler, which is preferable when working with high-output engines — especially turbocharged, supercharged, and nitrous-fed engines. The higher cylinder pressures and temperatures generated by these power-adder engines demand a colder plug that can dissipate the heat rapidly enough to avoid over heating of the ground strap, center electrode and insulator nose which can all lead to pre-ignition. Colder heat range spark plugs are often recommended for maximum effort applications as they allow for better tuning flexibility and timing input.
Higher heat range spark plugs are generally reserved for street-driven engines that normally do not generate these elevated cylinder temperatures. Heat range is a fine balance, you don’t want a spark plug heat range that is too cold but you also don’t want a spark plug heat range that is too hot. When you have the proper heat range, the insulator is operating at a temperature that it is able to burn off carbon and combustion deposits, combating fouling of a spark plug. If a heat range is too cold it can lead to excess carbon deposits which can foul the spark plug and cause it to not function properly. If too hot of a heat range is used, you can cause serious damage to your engine due to pre-ignition.
Heat Ranges With Ethanol
It’s not common knowledge in the performance industry that when using ethanol-based fuels, it is a requirement to run a very cold spark plug since fuel lights off very easily once it reaches its operating temperature. Cold spark plugs are necessary to prevent pre-ignition damage to engines using this type of fuel. Brisk spark plugs can offer a wide heat range selection for most of the popular spark plug designs.
Still investigating the variances in spark plugs, there are a couple more options involved with spark plug design that deals with the position of the center electrode relative to the spark plug body. Older generation engines, from the ‘50s onward, placed the center electrode roughly even with the end of the thread reach using a short ground strap electrode. This is referred to commonly as a “non-projected” spark plug. As engine performance and efficiency improved, and certainly, with modern engines, combustion research proved that projecting the center electrode further into the combustion chamber and away from the end of the thread reach is a beneficial move for combustion efficiency on OEM applications.
This is part of an effort to place the spark discharge for combustion as close as possible to the center of the combustion chamber. Some vehicles even use “extended projection” spark plugs, as engineers position the ignition source closer to the center of the combustion chamber. Conversely, for high-performance and racing engines, non-projected plugs offer huge benefits. Non-projected tip spark plugs allow for tuners to be more aggressive with ignition timing curves often allowing them to increase power through tuning. Non-projected tip spark plugs are also retracted a bit from the harsh turbulent environment in the combustion chamber often increasing durability and consistency.
There is almost a cult of mystery, intrigue, and urban myths surrounding spark plugs that seem to survive the best efforts of better education and the passage of time. Many of these myths continue to be passed along with very little regard for accuracy or even common sense. Spark plugs seem to be a common area for concern because they can be easily accessed (as opposed to internal engine components) and therefore gain mythical abilities because of their ease of access.
Brisk Part Numbering System
Example: DOR15YTE-1: This is a 14mm spark plug for an engine using an aftermarket aluminum head that requires a crush steel gasket and offers a 0.750-inch thread reach with a triple ground electrode. This heat range of 15 is near the middle of the Brisk heat range chart.
SHELL – there are 12 different shell configurations A-B-D-F-G-H-J-K-L-N-P-U
D = 14mm x 1.25 thread pitch, with 5/8-inch hex, gasket seat, with 0.750-inch thread reach
O = Does not comply with ISO standards
R = interference suppression
17 = Heat Range — range is from 08 (cold) to 19 (hot)
Y = Projected Nose
L = Extremely Projected Nose
T = Projected nose with three ground electrodes
Z = Two auxiliary electrodes – Premium
LT = Extreme projected nose with three ground electrodes
S = Silver center electrode
P = Platinum center electrode
PP = Platinum for both center and ground contact point
YTE = Yttrium Alloy Electrode
-05 = 0.5mm (0.019-inch)
-1 = 0.4 – 0.9mm (0.15 – 0.035-inch)
-3 = 1.3mm (0.050-inch)
-X = Special Order
A Brisk DOR15YTE-1 spark plug would be:
14mm x 1.25 thread pitch with a tapered seat, a 0.750 thread reach, a resistance style plug with a Yttrium alloy with three ground electrodes, and 0.035-inch spark plug gaps.
One recent claim is that precious metal spark plugs such as iridium or platinum should never be used in a supercharged application. The myth contends that these materials act like glow plugs and will cause serious pre-ignition damage. As with all assertions like these, there is a tiny bit of truth mixed in with the myth.
Precious metal spark plugs such as iridium, platinum, or yttrium materials aren’t all bad. They are very commonly used for OEM applications to provide a very durable and long-lasting lifespan for end users. A few examples of high-performance engines that utilize precious metal spark plugs for OEM include Chevrolet’s LT4 and the supercharged Dodge HEMI Hellcat. These manufacturers certainly would not use a precious metal spark plug as original equipment in the engines if they were guaranteed to be problematic.
Keep in mind, as mentioned earlier, these precious metals are used very sparingly in a spark plug. Only the very small tip of the center electrode is actually platinum or iridium. The remaining portion of the center electrode is most commonly nickel, with a very small percentage being copper. Precious metal spark plugs can be more conducive to creating hot spots in modified, high-performance applications used for racing, especially forced induction engines, and precious metal spark plugs should never be used in a nitrous engine.
Precious metals are very hard and don’t wear like softer metals such as copper, nickel, or silver. The tradeoff is that precious metal spark plugs like iridium use a very small amount of the material which is generally affixed to the very tip of the center electrode. Because of the very fine tip and the poor thermal conductivity property of iridium, these plugs do not dissipate heat very effectively and are more prone to becoming a hot spot.
This is why high-performance and racing engines generally use copper or silver center electrode spark plugs. Brisk specializes in silver center electrode technology, silver is the best conductor of thermal heat and is also the best conductor of electricity. Using silver provides the maximum heat dissipation which allows for more aggressive tuning and also provides a very potent spark discharge to ensure a rapid and complete burn of the air/fuel mixture improving power and efficiency.
Any spark plug used in a modified supercharged, turbocharged, or nitrous situation should minimize the overall projection into the combustion chamber, including the center electrode, ground electrode, and the ground strap. Projected insulator tip spark plugs are more prone to causing pre-ignition with extreme power adder applications. This is why most all power-adder engines with extreme cylinder pressures should use a non-projected nose or a surface-gap style spark plug.
The truth is, a properly chosen spark plug configuration with the correct heat range and plug gap will be all you really need in the search for optimizing performance. Spark plugs should be considered a consumable commodity and can be used as a tuning tool to bring out the best in performance. Now that you have a better understanding of how spark plugs and Brisk plugs specifically achieve these points, you can make a much more informed decision for your next set of plugs.