Q. Why should I use discs?
SuperTrapp discs provide a scavenging effect. Here’s how it works: the gap between each disc ranges from .023 inches wide on the inside of the muffler, to .028 inches on the external open edge. As hot exhaust gases pass through the discs to exit the muffler they enter a larger area, creating a slight pressure drop as the gas expands, creating a scavenging effect. This larger charge lets the engine create more power and this is why it is very important to use discs. It’s simple physics and math: a quantity of gas expanding to fill a larger volume results in a reduction of pressure and as the circumference of the circle increases, its area increases by more than twice as much.

Q. How many diffuser discs should I run?
The answer depends on your displacement: disc diameter, power band, and noise level. Fewer discs reduce sound levels, more discs increase sound levels. Fewer discs increase low-end torque and richen the carbureted fuel mixture. More discs increase sound levels, increase top-end power and lean out the carbureted fuel mixture. NOTE: When tuning an exhaust system, start with fewer discs and add. Never start with a lot of discs and subtract. Generally on a stock set up (no engine modifications, and stock carb and air filter), you can start with six to eight discs on dirt bikes and ATVs. On V-twin, metric and cruiser bikes, start with twelve discs. A popular misconception: The more free-flowing an exhaust system is, the more power it will make. This is not true. Some backpressure (2-3 PSI) is necessary to achieve maximum power. This is why it is necessary to use the discs that come with your tunable SuperTrapp exhaust. The number of discs to use will depend on your application, displacement, disc diameter and power band. To assess the performance of any product that affects horsepower and torque, lap times and Dyno- runs are your best indicators. However, since most enthusiasts usually only have a “seat-of-the-pants” Dyno, running condition is the most obvious indicator. Pay attention to the coloration of the discs. Little or no disc coloration indicates a possible lean condition (remove one or two discs). Black or sooty discs are indicative of a rich, or oil burning condition (add one or two discs). Discs that turn a tan or golden color indicate an acceptable balance of fuel mixture and exhaust flow. Reading a spark plug is the quickest way to check if everything in the engine is working as it should. And, it will tell if the SuperTrapp has been tuned properly. A rust-brown spark plug color indicates that the plug is operating smoothly (exhaust is tuned correctly). A whitish look indicates that the burn is too lean (remove one or two discs). A blackish deposit on the plug electrodes (left by oil or fuel traces) indicates that the burn is too rich (add one or two discs).