Yet another disc question (surprised?)

[dmassey]

My set up is:
2010 HD FLHTK w/ mostly standard 103. Modifications are: SE Fatshotz (duals), V&H head pipes w/ power chamber, SE high flow breather, SE Race Tuner. Final dyno pull: 80.11 RWHP, 96.06(?) FP Torque @ 6200 RPM. I looked for my dyno sheet in hopes of sending to you but couldn't find it. Most of my riding is 2 up - my wife really likes to ride with me which I enjoy. Mostly Interstate cruising around 70 MPH. Living in NE Tennesse though we certainly take to the mountains every chance we get. Was down in the Smokies just last weekend. The torque curve is a smooth climb and peaks at around 5.6 - 6K RPM if memory serves correctly. Much of my riding is arond 2.5 - 3.2 K RPM and I would like the torque curve to be a little steeper meaning that the torque is building sooner and quicker. By no means am I wanting to do any "neck snapping" or anything like that. I think that to increase the torque I would need to take out disc. Correct? The stock number of disc are 11/muffler. We didn't do any disc work when dynoing. How many disc should I remove - or add?
Thanks,
Danny

[kz550]

Q. How do the diffuser discs work?
SuperTrapp is the original tunable muffler. The SuperTrapp exhaust system allows you to adjust, or “fine tune,” the sound level, powerband and performance. SuperTrapp’s exhaust outlet is formed by a precise gap between a series of individual discs. Adding discs increases the size of the exhaust outlet, increases exhaust flow and exhaust tone while reducing backpressure. More discs move the power band up to give you more top-end power, and lean out the carbureted fuel mixture. Removing discs decreases the size of the exhaust outlet, decreases exhaust tone, and exhaust flow while backpressure is increased. Fewer discs tend to increase low-end torque and richen the carbureted fuel mixture. Diffuser discs allow you to compensate for changes in altitude and air temperature without re-jetting or changing your air intake.
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Your present AFR will test the limits of how few and how many more diffuser discs you attempt to run. SuperTrapp gurus suggest removing/adding two at a time, riding, then fine tuning down to the last one. I've found on my 900cc sportbikes that there are three different number of diffuser configurations I can run depending on what I'm looking for. But the one I like the best is a compromise. Both bikes are equipped with the same SuperTrapp exhaust and nearly identical jetting. One has 7 discs, the other has 9 discs. However, in my case, more important than the number is the distance from the outlet to the end-cap, which in both cases is 9/16" exactly

[dmassey]

I'll take out a couple and see what happens. Thanks for the info. Incedently it has the open end cap.

[andyv]

SuperTrapp is the original tunable muffler. . ... However, in my case, more important than the number is the distance from the outlet to the end-cap, which in both cases is 9/16" exactly [/IMG]

Why is this distance more important than the number of discs???

[kz550]

Why is this distance more important than the number of discs???

It just worked out that way. The older bike (foreground) had many combinations applied to it in 2009 until settling on 9. The newer bike (background) was rejetted closely to the first (only difference are 1% richer main jets), but was flat on top at 9 diffusers, stronger with 8 and pulled relentlessly with 7. One day I pulled out a caliper measuring tool to compare the two exhausts.

You get loyal to a product when you follow their tuning guide under two independent situations, finding the combination that works out best for each instance and come to find results like this. The older bike/exhaust has an older set of diffusers that have been visibly compressed, while the newer bike/exhaust aren't. Which is why I say 'in my case.'

For an open end cap and 11 discs, I'd say there's probably a lot of room to play with.

[bschultz]

Just a word of thanks KZ.
I personally appreciate and enjoy your comments. Your "real world" experience and input are always welcome.

[dmassey]

Q. How do the diffuser discs work?
SuperTrapp is the original tunable muffler. The SuperTrapp exhaust system allows you to adjust, or “fine tune,” the sound level, powerband and performance. SuperTrapp’s exhaust outlet is formed by a precise gap between a series of individual discs. Adding discs increases the size of the exhaust outlet, increases exhaust flow and exhaust tone while reducing backpressure. More discs move the power band up to give you more top-end power, and lean out the carbureted fuel mixture. Removing discs decreases the size of the exhaust outlet, decreases exhaust tone, and exhaust flow while backpressure is increased. Fewer discs tend to increase low-end torque and richen the carbureted fuel mixture. Diffuser discs allow you to compensate for changes in altitude and air temperature without re-jetting or changing your air intake.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Your present AFR will test the limits of how few and how many more diffuser discs you attempt to run. SuperTrapp gurus suggest removing/adding two at a time, riding, then fine tuning down to the last one. I've found on my 900cc sportbikes that there are three different number of diffuser configurations I can run depending on what I'm looking for. But the one I like the best is a compromise. Both bikes are equipped with the same SuperTrapp exhaust and nearly identical jetting. One has 7 discs, the other has 9 discs. However, in my case, more important than the number is the distance from the outlet to the end-cap, which in both cases is 9/16" exactly

Took two disc out of each muffler last night. Rode to work this morning and will be riding this weekend - 10K service interval due. I'll see how it does and if I need to take out a couple more. Thanks for sharing your experience and insights!
Danny