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View Full Version : 250SX w/Uni-filter and Supertrapp ??



Woodsrider
06-24-2010, 07:42 PM
I just got an ES for parts and the engine is sweet. I will put it into an '85 SX .I will use SX carb(I guess they're the same anyway) because I just rebuilt it. I have a Uni-Filter and a Supertrapp for it.
I have 8 discs...is that a good number to use. I'm not a racer...I just like playing around on the trails....not too worried about top speed...I just want it to work good. It's my first Supertrapp and I'm looking for some input from others with the same/similar set-up to see what others have settled on for number of discs. I weigh 205 lbs and am just trying to get some input on the number of discs to try for the first ride.
Am I correct in thinking less discs = less noise and more bottom end grunt....more discs = more noise and more top end power ?

Chillian
06-24-2010, 08:52 PM
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).

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Woodsrider
06-25-2010, 07:07 PM
I guess what I'm looking for is what others are using for the number of discs with same engine/machine as me. As stated before, I only have 8 discs....and if others are happy within the 6 - 9 range...I'll not bother looking for more discs....but if everybody is running 12 discs, then I would like to have a few extra in my possession when I put this thing together so it's ready to ride. Maybe there is a better starting point for this machine than just a "generic" 6-8 discs.