2nd outlet on stock SC muffler?

[montroe]

I have been told that I can get a deeper sound from my 1978 SC by adding a second outlet to my stock muffler. Does anyone have positive or negative feedback on doing this?

[dickster]

try a search there's been loads on this recently.

i don't have the threads to hand

[Kurt B]

I just did a dual outlet on my 84 muffler, but I closed the main and added two down the center. In your case, just cut a hole and add another pipe. I have redone mine, changing the angles of the out pipes, so I can post a pic later. Also, I will post a picture of the SC muffler I have lying around that someone added another danske style pipe on the right side so you can see what they did.

[Doug Zielke]

Originally posted by montroe
I have been told that I can get a deeper sound from my 1978 SC by adding a second outlet to my stock muffler.

Deeper???
Surely, louder.

[Kurt B]

Doug, it's actually deeper more than just louder...depending on the pipes you add. I'm discovering this as I go! I've got lots of paired various pipes from Pep Boys floating around the garage now...thankfully, they're cheap!

[Kevin Stewart]

I did a c2 conversion and added the extra outlet it is louder and deeper, sounds great, heres a picture, Kevin

[RarlyL8]

There are a few different ways to do this depending on the sound you desire.

The hard way is to take the muffler apart and rearange the guts to be a true dual outlet muffler with equal bank pressures.

The easy way is to simply drill a hole on the passengers side and add a tip. If you do this start small, about 1/2 inch, and progressively go bigger until you get the sound you want. Nice part is it's easily reversible.

[911pcars]

"The easy way is to simply drill a hole on the passengers side and add a tip. If you do this start small, about 1/2 inch, and progressively go bigger until you get the sound you want. Nice part is it's easily reversible."

Just wondering. If instead of drilling a single hole, one were to drill a series of small holes equivalent in area, would there be any difference in the pitch, loudness or gas flow? Reason why: plugging several small holes is easier to accomplish then reducing the size of a 1" dia. hole.

Thanks,
Sherwood Lee
http://members.rennlist.org/911pcars
www.seinesystems.com

[Bob Goding]

If you go back and do a search, you will learn that the right end
chamber of the muffler is actually just an expansion chamber,and drilling in to it will let out a hell of a lot more noise than power.
That's why the recommendation to start with a 1/2" hole and open up till you get the sound you want---then weld on the tailpipe. Takes a bit of understanding the muffler dynamics---
but picture it same as a 'normal' exhaust system ---first, all the gasses from the exchangers go thru the initial sound deadening chamber in the middle,then across to the subject expansion chamber ,on the right, then back thru to the final 'muffler bit on the left and then out the pipe , so the gas flow is kinda different at both ends of the banana.--Hope this makes sense.----[ I also hope it is correct !!] Can someone cut open an old muffler and post some pics of the guts,
to clarify this for all of us,please---I cant afford to hack into my
muffler till I get something good to hang on the ssi's-----any update on the supposed ssi muffler, anyone?

Bob

[APKhaos]

Following muffler anatomy notes provided by Prof. Rarlyl8
The subject cadaver was a stock '73 hotdog:

-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.

[Steve W]

That sounds like the description of a dual in, single out muffler for the pre 74/SSI heat exchangers. I believe the post '73 single in/single out have a different baffling layout, but I don't know. Does anyone out there know?

[RarlyL8]

Steve's right, the muffler I described is a pre-74 unit. Can't say for sure if the stock '78SC is the same inside, but it should be quite similar.

Thanks for posting that long winded muffler thesis, Tony. One of Warren's pictures would have said it all in a lot less space (I really need to get a scanner).

Drilling several holes instead of one gives you a bad sound - like a rusted out muffler. If you do go too far drilling one large hole it can be easily capped by welding a round piece of metal over it.
The sound with an initial 1/2 inch hole, welded tips, and a set of SSIs is very nice. Not loud but throaty. Just more of a good thing.

Yes, I found this all out the hard way.

[APKhaos]

There are a series of pics of an opened 1 in 1 out stock muffler being modified to 2 out - they are buried in a thread some time last year. Can't find them, despite many cycles on Warrens search engine.

The process involved moving some baffles & pipes to create a more balanced flow across the two outlets.
If you are serious about this, they are really valuable.

[epbrown]

I remember that. I think it was Bill Verberg that posted pictures, though. And was it in a recent thread with Dan Novak (DANNOV), who performed a similar mod to his 85 Targa?

Emanuel

[Kurt B]

The article I used can be found here

http://www.911t.org/WklyReprint/modified_muffler.htm

This makes dual out center. Here's picts of the throwaway I bought to check out.


then obviously, what I chose to do. The pipes look a lot better straight out than slightly up.

[Steve W]

Has anyone ever heard anything about the muffler Andial has exclusively manufactured for them in Switzerland? They also have a dual out version. They claim a 5~7 hp increase, which I believe because as Porsche Sports of N.A. they do not exaggerate hp gains. They also have a muffler for pre-74s which has me curious. These pics come from their site: