Muffler guts!

What is inside a muffler. How are the baffels and chambers aranged in a 1973 911 two in and one out muffler and how about the insides of a "sport muffler" the one with the two pipes comming out the back down low spaced about as wide as the licence plate.

Never replaced one so I've never had one to cut up and living rural checking out the Porsche shops is not an option.

Randy Jones
1971 911

Randy,

The center portion contains the baffles and each end houses an expansion chamber. This makes it possible to weld a right outlet on if you want, without dissassembly and rerouting.

I just happen to have such a muffer for sale. See my post in the parts for sale section:

http://www.pelicanparts.com/ultimate/Forum12/HTML/002354.html

Hope this helps,
Nick.

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Nick Shumaker
1982 911SC Coupe

RLJ Iam in the middle of doing my second muffler and I cut the top off mine and rerout the inside.I remove all the fiberglass and steal wool. Then I cut the center baffels out add a pipe on one side then plum two exit pipe's out the center side by side like a boxter you wind up making a two camber system that flows evenley and has a real nice tone not to loud just right lookes cool to!!

Hey greg K. Want to build me one and sell it to me. I have a 72 911. I'm about to repaint my car. I have a fiberglass rear bumper with no cutouts. I have been trying to locate a used boxter muffler to modify it to fit my 72. To expensive though. I love the way the outlets come straight out the back. Let me know if would want to do this. let me know a price. Thanks
My email is lsolon@ixl.com

Randy - I will try to describe the inards of the stock '73 hotdog for you. Get a pen and paper and try to follow along (I find it really hard to communicate things this way).

-All descriptions are from the perspective of standing behind the car, looking at the muffler. The stock exhaust tip will exit on the left, or drivers side.

-Draw the hotdog with the tailpipe exiting the middle of the left side end. The dual inlets come in near the bottom on the other side of the muffler (from this view). You know about how far they are spaced.

-Inside there are 5 baffles. The baffles at each end are complete circles arranged vertically. This leaves 3 baffles evenly spaced in the middle. Don't draw the middle ones yet. Draw a dotted line horizontally thru the muffler at the midline. The middle 3 baffles are half circles oriented vertically (like the end ones). They extend from the top of the muffler down to a little past the imaginary dotted midline. I will refer to these baffles by number 1-5, #5 being the full circle baffle nearest the tailpipe, #1 being the full circle baffle at the oposite end.

-At the bottom (flat part) of the middle 3 baffles (#2-4)is a metal screen or grading. It disects the muffler horizontally, and connects all 3 baffles at their bottom. This devider is mesh between baffles 3 and 2, and is solid between baffles 4 and 3.

-At the top of the muffler there is a pipe or tube that extends horizontally from end to end thru all 5 baffles. One end terminates at the tail pipe, the other just past the oposite end of baffle #1.

-A second tube runs along side the first, it is much shorter. The second tube goes thru baffle #1 and #2 only.

-The space at the end of the muffler past baffle #1 is a hollow chamber. The oposite chamber end (#5) is packed.

-The exhaust flows as such: exhaust enters the 2 bottom inlets and mixes in the bottom of the muffler between baffles #2-4. It then goes thru the metal screen between #3 and #4. From there it enters the short tube and goes to the empty chamber. It then enters the long tube and heads for the tailpipe.

-The sport muffler puts dual tailpipes at the bottom of the muffler between baffles #2 and 4. The bottom of the metal plate between baffle #4 and 3 must be pierced as well at baffle #4 itself so some muffling can be utilized. Now you pretty much have a strait shot from the inlets to the outlets. This is why they are so loud.

I hope you can visualize this. Wish I had taken some pictures last time I had one of these things cracked open.

Hey Rarly - - This is perfect - thanks for the description of the guts.
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I now understand why, in the other thread, you said drilling small hole in the right hand side, when adding the second outlet, will significantly increase the loudness - it is the unpacked side - presumabley, the noise suppression comes just as the gases exit through the left-hand, packed chamber. Your description also explains why adding the second outlet on the right hand side maintains equal back pressure at both inlets - - - the gases from the two inlets are comingling between baffles 2 and 4.
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Question: What happens between baffles 4 and 5, and between 1 and 2, both on the lower and upper halves?
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And finally, the Baffles - are these steel plates with holes drilled through them?
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Thanks again for this description. It's very helpful.
Chuck
83SC


[This message has been edited by patalive (edited 02-20-2001).]

The space under baffles 4-2 is empty. Both sides of the cars exhaust enter here and mix. The exhaust then goes up thru the grading between baffles 3 & 2, then enters the short tube heading right tward the open end chamber. The spaces between the baffles in the upper part of the muffler are tightly packed with sound deadening material. When you open up the right side chamber for a second tailpipe the only muffling to that point is between baffle 2 & 1. If the hole is small, then the majority of the exhaust still has to go thru 3 packed chambers to get to the left side tail pipe. In order to make this muffler true duals you must do a lot of re-aranging and weld in a new baffle in the middle to devide the two halves.

Gotcha! Thanks for the clarificaton. I think I'll still opt for the easy solution, i.e., the smaller hole on the right side. If it gets too loud on the street, there is always JackO's solution of jamming a tennis ball up the right side outlet. He claims the ball doesn't melt from the heat.
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Chuck
83SC

Does anyone know a source for 3 or 4-inch oval muffler tips, like on some of the after market dual exhausts (like on the B&B Triflow)? I got my car with a dual exhaust (one on each side, not sure of the brand), and it has the standard-looking round tips with an outward-rolled edge. This post make me think I could just have new tips welded in if I could find them.

Thanks,

Olivier
82 SC

Anyone know of any sources?