'Gutting" a factory muffller...

[Tilikum Turbo]

Greetings all,
I run a CAT and factory muffler here in Southern California(86 930 engine).

Has anyone had experience in having a shop or themselves literally open up the factory muffler, and gut it, and re-install instead of buying a sport muffler.

I really DON'T want to have an aftermarket look, since I like the factory twin-black pipes coming out back, and I will not run a Zork, or twin outlet valance.

Any suggestions, or feedback?

[spence88mph]

I haven't done this to a 911 muffler but I have gutted a few motorbike mufflers with good results. People would de baffle Aprilia RS250 pipes and get a decent increase in performance when rules wouldn't allow for aftermarket pipes, I also debaffled a Ducati Monster recently and it worked a treat (sound wise) and looked totally stock. There's a few other cars that do it with great results, like I think it's a common mod on AMG 55s to get a few more ponies.

I would say the flow path would be all over the place in the 930 muffler if you just gut and leave it, you might be best to open it right up, gut it then weld in a straight pipe (maybe perforated) in there and close it up, it should give you good results.

[agrimmitt]

I have done what you are talking about. First on an early 911, then on a 914-6 and current on one of my exhaust systems used on my 83sc>RS clone. The early mufflers I feel were easier to work with, open from the top and return or baffle to taste. The later system have more supports and rivets holding them together. You need to be a better than average welder it try it yourself; and your local muffler shop is not where I would take it then. And in CA, smog regulation doesn't permit them>right. Take it to a local "quality" welding shop have them open it above the top of the center seem. Then remove what you please, but have them add some cross supports and some "c" shaped material to cover from within a CHP officer running a piece of metal into the pipe and not hitting something. It is going to be loud>period with some increase in hp; but what is only a guess. In the mid to late 70's Pano ran an article showing how to do turn a 911 exhaust into a "sports" exhaust. I think I still have a name/address/# of a guy in Nev. who is an amazing welder and builds custom track exhaust system to meet DB levels at some of the track. Good luck and enjoy; o'ya have you filling checked by your dentist before reinstalling the exhaust system!
art
agrimmitt@pelican

[RarlyL8]

This will not be simple to do correctly as there are 2 flame tubes and associated baffles, plates, mesh, etc inside of an odd shaped housing. If you just cut open the muffler and gut it the sound will not be good.
If it is just the look you are after you may consider grafting a set of tailpipes onto an aftermarket muffler.

[911st]

Not a 930 muffler but yy attempts at gutting or modifying a 911 muffler never went very well.

First attempt I cut it open with a torch and the heat warped things a bunch. Had to use a lot of clamps to try to get it back together.

Second attempts used a cut off wheel. Found shell was double layer complicating things. Had a muffler shop weld it back up after my mods. Plugged inlets and put a shop vac on the tail pipe it to pressurize it and it had holes all over the welds.

People have been successfully modifying 911 mufflers for a long time. It just did not work well for me.

[xbmwguy]

i bought one on ebay. sounded very good not too loud picked up some power and kept the stock look. its in the attic now but its not made to run with a cat

[ronster]

Sportech, in Campbell, CA, does this and they sound very good without the drone usually associated with the "sport" mufflers and no emission problems. They remove about 65% of the baffles. On a 986 Boxster they charge $695 for a swap out. They claim, when done with headers (they use Chinese eBay headers of which they've been running for two years with no incident) an 11 hp increase. The headers and header installation runs the cost to around $1K.

[911st]

Are you talking about keeping the cat and gutting the muffler?

[RichardE]

My 89LE ( so SE flatnose setup) twin pipe system had a factory muffler that was shot so I found a top engineer here who pulled the whole thing apart and rebuilt it. My option was to buy from UK an exact replacement at a cost of, from memory, 2400 pounds. Like $7500 our money so a no brainer. The engineer has done a brilliant job plus I had it HPC coated ( ceramic aluminium ) to reduce heat effect in the rear. Biggest issue I think he had was finding stainless wool packing of good quality but you shouldn't have that problem in the US.?? Not sure.

[Schwarzeritter]

1. Just don't! Drone, Disapointment, and the shame of running a gutted system.

2. It's possible to rebuild or restore original systems. It's also possible to make modifications during the restoration to change tone and so on.

3. Spend the proper money on you're machine and get the high quality aftermarket, get the quality and respect, self respect.

A. You have money, you buy Inconel or Titanium, or if you haven't you have a system made from T309, the materials used inside of a muffler are diversifed and depend on the system and so on.

B. Inconel tends to hold a organic tone, and Titanium a metalic sound.
The T309 is deffinitly organic in tone. You will not regret the T309, it's pretty standard amongest a lot of Ferrari exhuast makers. Very nice look too. You're 930 is white, so the delicate super-plished glow of the T309 will surfice and withstand the extremes a turbo application can place on lesser materials.

We really only do three materials, Titanium, Inconel, T309. Well boys, I am off, for some coffee.

[RarlyL8]

Folks throw those mufflers away so it should be easy to find one to play with if that is your desire. I am sure it could be made to work.
The CAT is the true issue. With that in place there is little hope of significantly improving performance on the muffler side. I've been playing with CATs in hopes of building a nice system for those desiring such. Even the "sport" cats kill performance on these turbo cars, and they sound terrible.

[WERK I]

Originally Posted by RarlyL8

.................snipped for space.......
If it is just the look you are after you may consider grafting a set of tailpipes onto an aftermarket muffler.

+1
A much better approach than an experimental surgical removal of baffles and hoping for the best.

[Schwarzeritter]

I agree with Rarly, going with a high quality cyatalist is most pragmatic.
Rarly has some nice work, perhaps he can package something for you're
machine a Cayatalist and Muffler.