I had a buddy do the Fister D style mod to a pair of spare mufflers. When I installed them, I found it too loud for me. At the same time I added Topgear 200 cell cats and Topgear headers. Most people I believe would have liked the sound. There was no drone and were quiet when cruising. Under load and hard acceleration I found them a little too loud. I felt as if I were saying to the police officer around the corner observing traffic, "Get ready here I come! Be there in a second."
I have not had a speeding ticket since I was 18, a mere 41 years ago! don't want to start collecting them now.
I came up with a simple hack for the modded mufflers to tone them down and possibly dial them in to my liking.
The parts consisted of a thumb screw with 1/4-20 threads, another bolt with 1/4 threads which I cut the head off, a fender washer just a little smaller than the ID of the bypass mod pipe and a couple 1/4-20 nylock nuts.
I sliced the shank of the thumb screw and the bolt down the center so they would slide over the center of the fender washer. I added one nylock nut to the thumb screw before sliding it onto the fender washer. I then tack welded the the shanks to the fender washer.
Next, I drilled a hole straight thru the bypass pipe just large enough for the 1/4-20 threaded shank to slide into. I then used a cutoff wheel to slice across the drilled hole and opened it up enough until the fender washer/threaded rod combo would pass thru to the inside of the bypass pipe. Now what I had was like a dampner that I could open/close or anywhere in between inside the bypass pipe. I put a nylock nut on the backside and the other nylock nut works as a jamb nut to lock it in position. As you'll see I painted the end products with Chevy orange engine paint I had laying around.
Lastly, I had to close up the gap left by the slot I sliced to install this into the pipe. At first I considered welding it up, but didn't want to risk any weld getting inside and jambing things up. I decided to use JB Weld to close it up. I put a narrow piece of tape over the slots to keep the JB Weld from getting inside. It is not pretty and I've yet to install them, but we'll see how it works out. I set the angle of the pipe dampner at about 1/2 open/close. They are easy to rotate by just loosening the jamb nut a hair.
Here are some pictures which I hope will help make sense of my attempt of a description.

 

Really curious to see how well this works and whether it lasts....Thanks for sharing.

 

Very cool mod. Thanks for sharing. I too will be interested to see if the JB withstands the heat. Keep us updated!

I do have one minor criticism though. It's a 996 so you have to use metric and if you can't use a 10,13,15,16,17,18, or 19mm on it then you are using the wrong size.

 

I have used this poor mans adjustable baffle hack many times back in the day, it works well. You could have put it in from the inside (without cutting the slot), about 2" from ether end, if you had known you were going to need it before welding the bypass pipe into place. Hope the JB weld holds....

 

Could you not just get that section mig welded for cheap instead of JB weld?

 

I just threw this together with what I had on hand, literally in an hour from thought to done. It definitely can be improved on in a lot of ways. I want to see how well it works.
If I were to do it all over again it would all be in stainless, installed in the pipe before welded onto the muffler and lastly with metric sizes.

 

Since it's already there we might as well see if it holds. I would never try it but who knows, it may be brilliant.

 

it's creative, that's for sure

 

Have you compared the exhaust operating temperature to the temperature that JB weld (500F-600F) and the nylon in the nylock nuts (250F) deteriorate?

 

 

All very good questions.
I plan to swap the mufflers out and will run them through the spring and summer. We'll see if it will be worth a complete do over upgrade next winter.

 

These look to be used to get some back pressure restored due to the straight pipes losing bottom end torque?

 

 

 

Nice ebay find and thanks for the info Radium King.