Supertrapp disc question

[misfitJason]

 Currently running a v111 motor in my Softail with a Thunderheader, and it is loud.  I had a kerker supermeg on it before and it was just as loud.  Again though, just louder than my preference.

My kerker head pipe fits a a supertrapp internal disc muffler that I picked up. Now I know it needs to flow pretty well. The muffler is a 3 inch disc type.  I figured I would start with 15 discs and an open endcap. Any recommendations from you guys.

[kd]

First of all go to the SuperTrapp site and do some reading.  They are very forthcoming with the information.  It will help you decide how to move forward properly (not just on guess work). 

Someone may chime in with what worked for them but each engine is different and dyno tuning as you work through the disc count may be your best option. Sadly, you will need a supply of discs (with the appropriate length of mounting screws) and may not use them all. You will have the option of a closed or open end cap.  More stuff you may not use one of.

I found out on my 4" discs the hole i8n the open end cap is equal to 10 - 12 discs.  A lock washer between the discs is approximately equivalent to 3 discs.

[Barrett]

That seems like a good starting point. Adding and subtracting is the best way to find the sweet spot.
I use a cordless drill and it makes it a quick job.

[nmainehunter]

I adapted the SuperTrapp discs to my Bassanni road rage system. I did it to get rid of the decel pop. I couldn't jet it out. I feel it is a great move for me, the pop is gone and I believe it improved the performance. I've played with it and have settled on 12 discs with the closed end cap. I also run an EV27 Cam, Wiseco 10-1 pistons, Andrews valve springs a Dynatec Ignition and a Mikuni for my 95 FX Springer.

[GD]

I run a 2 into 1 Supertrapp exhaust on my 05 Roadglide with a 95 inch motor Headquarters ported heads, Fueling reaper 574 cams, etc.
I started with 16 disks and closed end cap over a period of 2 years and a few pulls on the dyno i now run 22 disks with a closed end cap the motor likes this combination and it is quiet when cruising but does get a little loud when you are getting on it and having fun. I  like the performance of the Supertrapp and the noise level of the pipe more than when I was running a Thunderheader on the bike the Thunderheader performed well but was to loud for my liking.

[RTMike]

I would start with 24 disks and a closed end cap .That will put you close to what you need and a lot quiter

[kd]

   Search SuperTrapp exhaust in the dyno section and you will see the disc count on engines tuned on a dyno for optimum all around performance and rideability are quite high.  This may mean having the proper length screws and more discs on hand.  It's an added expense if you don't use them but a necessary evil.

[Coyote]

My 113 wanted 26 closed. So I'd start at 24 closed.

[Barrett]

Mine was a 4" disc.(measures 3.75" across) With 3" you would want more.
Supertrapp does have a forum.

[misfitJason]

Thank you gentlemen. I had no idea that they had such a wealth of knowledge on that site nor that they had a forum as well. I have accumulated about twenty five discs and different endcaps to help me along.

[kd]

I remember they confirm the open endcap is a 10 - 12 disc value.  I don't recall if it was 3 or 4" though. I used that info to calculate the area of the hole and determined how wide that tiny space is between the discs over 10 pieces.   That helped me determine my direction when going back and forth.   

It was also determined and shared by a tuner (or someone that was dyno tuning a SuperTrapp system) here on HTT several years ago that a #10 lock washer spacer between discs was comparable to 3 discs on the dyno. I also experimented with that when I didn't have enough to test a higher pack or needed longer disc fasteners to add discs.  This method at least helped me find the rate of change.

Adding an open end cap doesn't do much for toning down the exhaust sound level.  It will allow you to get a feeling for what the 10 -  12 disc effect is when testing.  Similarly, the washer method opens up the sound volume but on a lesser scale and may be more tolerable.  I used a combination of each throughout my testing and was happier with the closed end cap and un-spaced discs.  With the first 2 my stereo was just something mounted in the dash.  With a closed end cap barely at 1/2 volume is very useable at 3000 rpm and higher highway speeds. 

Setting up the sound level is very subjective between individuals.  I am using more than 40 4" discs with a closed cap on a high compression 120" engine with a 3" Burns exhaust and I love the snarl and decel note. It is definitely not offensive anymore.  It took some experimentation but I am over the top pleased.  I am glad I didn't take any short cuts.  It was time well spent.   You will at least have the options I have mentioned to help you make that decision, or to reverse that choice for any reason using the factors you learn from your personal experience. Be patient and you will succeed. 

[Barrett]

I used #8 flat washers. I should be cranking it up next week. Waiting on the sock for the fuel pickup.

[kd]

I used #8 flat washers. I should be cranking it up next week. Waiting on the sock for the fuel pickup.

My 4" discs use 10/24 fasteners so it requires #10 washers.  I found the flats interfered with the shape of the stamped form where they match each other in the stack and deformed them when tightened down so I opted to use the narrower locks.  As a side benefit they also added to the fastener tension to resist loosening under vibration.

[Finn]

IIRC my Evo has 24 and Twin Cam had 35 discs, both with closed end cap.

[itsafatboy]

I wanted to try the fuel moto muffler on my boarzilla , the fuel moto pipe is the oblong one with the disks ,  but no luck just finding the muffler for thier dyna pipe and i dont want to buy entire exhaust , oh well 

[misfitJason]

Well, despite supertrapp telling me it's a three inch one. It is not. It's a four inch. I ordered three inch discs and they are way to small. So I ordered some four inchers. The ones on it measure about 3.75. New closed endcap and discs on the way.

[RTMike]

Your heading in the right direction