Andre Roodnat

I like to add a touch of Grrrrrr!

First I was thinking about the RMB, but I like the tip of the S4 tail pipe and I want to keep the stock look. I’m curious what it will do to the sound if you take out the muffler contents.
Anyone did it? How/where did you open and how did you close up again?

MikeN

Have you ever thought of obtaining an '89 GT or '90-'95 factory twin-pipe
muffler? They flow and sound much better then the factory S4 oval, though not quite as load as an RMB. Look good/stock to. I like mine just because you get a great exhaust note, but not loud enough to drown out the sweet sound of the engine.....

Andre Roodnat

A friend of mine has the '90 S4 with the twin tips. It sounds better and darker than the S4 muffler. But if I like the oval tip better.

Jim_H

Get the oval RMB, then you get the look and save the weight.

heinrich

Andre, a local here welded his stock tip onto an RMB. Looks 100% stock.

Andre Roodnat

Heinrich, how does it sound? It probably doesn't make much of a difference while idling, but does it ad that certain blaaaaaaah!?

Did he just take everything out, or did he replace the pot by a pipe or something?

Sab

I actually got a stock S4 muffler from a fellow rennlist member to gut it and use it instead of an RMB. But I have not gotten around to do it. I guess there are two options, one to open up the muffler "belly" and gut it or to cut it out and rejoin all the plumming. It'll be hard to keep it all aligned though. Probably best to spot weld all the pipes on some sort of base before cutting the muffler out.

Jim bailey - 928 International

Andre your rear muffler has two pipes in and two pipes out , the oval tip is welded to the two out pipes . The simplest thing might be to simply cut out the muffler and replace with two pipes which connect the in pipes to the out pipes . Opening the muffler , removing baffles and welding it back together is a big ?? as to what it might sound like . The muffler would act more like a resonator and could easy have a loud vibration at certain engine speeds ( gutted catalytic convertors often have an unpleasant sound ) .

Sab

The only problem I see is that the two in and the two out pipes do not line up. So some custom plumming will be required.

Garth S

I installed a GT muffler in place of the 'oval' S4 issue - the sound is better, although a bit too civilized: Other than the two seperate tips, what's the internal difference between these units?
I'll soon have an opportunity to go inside the GT unit, as it had a patch welded over a corrosion spot on the lowest front end point: As everything on this muffler is stainless - except for the oval body wrap (go figure?), my buddy has offered to replace this carbon steel wrap with stainless - in essence, to make a lifetime muffler. However, after cutting the bottom away, if I were to replace the two internal perforated pipes with solid pipe (stainless), and close the unit up, would this equate to an RMB disguised as an oem GT muffler?
Andre, this seems much like what you want to do?

ATR-1

HI. I have cut open a 87 S4 rear muffler and the in pipes and out pipes are straight thru. There are no baffles. The pipes have 3/16 holes in there walls and the rest of the muffler is fibreglass matting. There is no restrictions at all. I gained no power from a RMB but it sure sounds good. Mike D

Andre Roodnat

So the guts are filled with fibreglass? That’s what I thought. Than the procedure of taking everything out will not be worth it I think. This will not increase the sound much. I think the best sounds are created by a hollow tube. When chosen the right diameter and length, it can amplify and create the right sound. The same principle as a basspipe in a ported speaker cabinet. It should probably not be oval though as the original muffler. I think your idea is the best Jim. Just cut out the muffler and replace it by a hollow tube. So no tubes within the muffler.
I don’t know what condensation would do in the tube though.

MikeN

Begs the question as to what the difference is between the oval tipped early S4 muffler, and the later twin pipe version? Why is the twin pipe a better sounding version........less fibreglass, less holes??

Andre Roodnat

Good point Mike.

Maybe the manuals or PET can reveal something.
Makes me curious.....

Earl Gillstrom

Andre,

There is one more option: The '87s have larger intermediate mufflers, that coupled with an RBM is quieter than a '88 or later setup with RMB but sounds as good. Then merge the RMB back to the original tip, although that may take away from the sweet RMB sound as you would have to shorten the pipes considerably for the stock look. I made my own RMB using 3" truck exhaust pipe 3" longer than the "stock" RMBs. The extra length is in the front so it terminates at the same place in the rear. I don't know if it changes the sound much, but it sounds good to me and even old ladies comment how good it sounds.
I do plan to try the '91 GT intermediate mufflers some time for comparison, but probably not soon.
'87 intermediate mufflers seem to go for ~$75 on Ebay in US.
Caution: '86.5 intermediate mufflers have the same part number in PET, but one side is ~3" shorter than '87s.