Got a tunable "Supertrapp" muffler designed specifically for the Savage off a parts bike I bought.  It even has the 10 degree bend at the inlet so it lines up with the header and mounts up to the stock mounting bracket clean and square.  

DBM - You need this Supertrapp muffler to add to the 7 mufflers you've already tested in your muffler shootout!  You'd have fun!  You'd have to test this one 6-7 times with your vacuum contraption!!  You can add/remove discs at the outlet to tune the muffler.  More discs, more open, more flow = louder.  Fewer disc, more restriction = quiter.

It currently has 5 discs installed.  Supertrapp's basic instructions suggest 6-8 discs for a stock Savage or else you have to rejet the carb richer if you install more than 8 discs.  I think you can stack up to 12 discs, and then there is also an option for a closed or open end cap.  This one has a closed end cap (default setup).  These things are like $700 brand new!  Whoa!

https://supertrapp.com/catalog/product/view/id/11326/s/supertrapp-728-50650-mega
phone-series-slip-ons-suzuki-ls650-svg-86-04-s40-05-16-chrome/category/2/

Anybody played with one of these?

Well dang it, Philly!  Why do you want the 1 part I’m most curious about too!?

I’m going to remove it today and see if I can get the end cap and discs removed.  I’m hoping the screws aren’t seized up.  I’m letting some PB Blaster do some work right now.

Side Note - I decided to blow off the fork brace for now, otherwise I might have offered you a trade.

Let me look at this thing.  I’ll share some photos in a separate post for you and the forum.  Agree, I’d never pay $700 new when a gently used Dyna muffler can be had for $50 or less.  But it’s clever how this thing is designed for the Savage and the muffler inlet aligns properly with the header pipe.

Dave - I think you've tried about everything!

I read an old post about it and seems people are/were using anywhere from 7 to 14 discs.  Do you recall how many discs was too loud for you?  The Supertrapp instuctions suggest 6-8 discs for the Savage.  This one only has 5 installed.  I can't see how the thing breathed with only 5. Honestly I can't see how the thing works with any number of discs - the gaps between discs are tiny.

I'm having trouble removing 2 of the 6 screws.  Justin O said he had the problem too back in the day.

FWIW, on my 750 Laverda we got to around 20 discs on the end of the megaphone before there was no difference between the open exhaust and the ST discs in power on the dyno.  However, the noise level was much more tolerable.



SuperTrapp used to make reverse-flow inserts with discs for the Kerker/Bassani/etc 4-1 exhausts back in the day.  My engine tuner made copies of those.  They did not have any fiberglass/ceramic wool packing, just the reverse flow tubes and discs on the end.

WIth the ST discs you can get an improvement in flow by stacking up the discs on the lathe and using a sharp boring bar to take out the small reverse lip on the interior that seems to be there for spark-arrestor purposes.  The discs have weight, so reducing the restriction so you can then drop the number of discs does help.

Paul, all the ST discs I've seen have been made to be used in their spark arrestors, and that small lip I mentioned makes the flow reverse to go between the discs and the space is very small between discs.  My presumption is the hot particles/sparks keep going past the gap to be trapped inside the ST or get lodged in the gap and lose their heat into the disc.  If you zoom in on this you can see the very small lip on the ID:

https://m.media-amazon.com/images/I/61Xj1jXaqXL._AC_SL1088_.jpg

Since the spark arrestor function wasn't needed on the race or street bikes using a very sharp tool bit in the lathe to turn off that reverse lip made the fit between the discs less restrictive so the same amount of flow could be had with fewer discs.  The discs are stainless steel and if the tool starts to rub instead of cut they'll work-harden.

Here is the patent document for the discs that has some detail drawings and text explaining how they work

https://patentimages.storage.googleapis.com/05/9f/8b/ee4282ad4cfa3d/US6467569...

I think you'd need to be careful about spacing the discs apart or you'll loose the circuitous path the gases must follow to exit the exhaust.  I'd expect that the straighter the path, the less energy (noise) the exhaust will lose.

Part of the noise attenuation is also due to the 360* exit.  If you stand directly behind a straight through muffler you get all the noise.  If you stand to the side you experience less of it.  So the ST discs will cause much of the exhaust to be directed away from the listener.  It is the same idea you'll see used on race vehicles where the sound meter is always in the same spot at the side of the track -- put a bit of a tip on the end of the exhaust to direct the noise to the side away from the meter.  The exhaust isn't really quieter, but it foxes the measurement.

Google Patents and the Euro patent office espace can turn up some very interesting information.

Keep in mind that the number of discs needed will vary with the diameter/circumference.  If you are using 3" discs you'll need a lot more of them to have similar restriction to a few 4/5/6" discs.

https://motoconstructor.com/graphics/exhaust/

If you look there I've got photos of the ST baffle insert that my friend copied, including a dimensioned photo and also the box labels in case someone wants a project to build their own:

The cap is the standard 4" ST steel truncated cone with a center hole for the retaining stud, so any exhaust has to leave via the discs.

No recordings of the sound are available as this was all back in the 1980s/90s.  My friend Steve (the CBR600/XS650 special) had one of the copies of the ST insert in that exhaust.  But that was 20 years ago too, and I can't recall how loud it was, though I'm pretty sure it definitely was not quiet.  But then he was not trying to make a very quiet street bike so he didn't experiment to see how quiet he could make it.

If I had known what I know now.....I might have been able to take the db of the Supertrapp down a bit.  That insert for the Supertrapp looks creative!

The muffler I built for my Cafe' bike has been pretty good.  It is a bit restrictive I believe - but the sound has been reasonable and it is a compact muffler.

It uses and Emgo chrome housing.  The first setup is what is shown in the photo posted here.  The first baffle is removable and it has a plug in the center - the exhaust enters the inside of the perforated pipe and then is forced to the outside into the area between the baffle and the muffler shell, then it has to enter back into the perforated pipe before it enters the rear baffle.  The rear baffle does the same - the exhaust enter the inside of the pile and then a plug in the center of the pipe forces the exhaust into the outside shell, and then it goes back into the perforated pipe before it exits.

This pipe worked OK and does a pretty good job of cutting the noise down.  The really hot exhaust gasses exiting the first baffle does make the outer shell really hot and the chrome has turned blue/black in a small area at the bottom where the chrome does not get a lot of airflow on the outside of the muffler.  I do believe the muffler was a bit restrictive at full throttle and high rpm - but that is OK as I don't go there  often.