Gutting stock muffler

[JBO]

Thinking of creating my own sport muffler. However, I'm not sure what to use to cut the muffler to get to the baffles, and I don't have a large tool set. Any hand tool that will work that is fairly inexpensive? Secondly, I don't have a welder and have never welded. Could a product like "cold steel" (which is a putty that hardens like steel and is good to 600 degrees) or JB Weld be used to put the cut out back on? If this is not feasible, anyone have any idea what a muffler place would charge to do this (and would they even be willing to do it)?

[Paul Crowther]

I'll bet whatever you do will a cause a small loss of power and may not even sound much better. Why not wait till you need to replace it THEN get a better sounding unit?
Paul

[Schrup]

So let me get this straight, you want to hack open your muffler, rip out the baffles, then JB weld it back together. Please post pics for our entertainment!!!

[juanbenae]

i'd have to say thats a bad idea. roll the windows down whilst you drive for better sound.

what year is your car? you might be better off getting a cat by-pass, or a euro pre-muffler. do searches (lower left is search option) for both here and read up on what might work best.

[Tim Hancock]

JBO, If you have an air compressor, you can use a die grinder with a 4" thin abrasive wheel. This will cut thru it easily. As far as the JB weld goes, I highly doubt that it will hold up. You need to find someone with a welder.

I have tig welded many aircraft exhaust systems (321 stainless). If the exhaust system is highly corroded and getting thin you may end up with cracking near the welds later down the road.

Look up welding services in your phone book.

I do not know enough about these engines yet ( I just purchased my first 911 and am on the bottom of the learning curve) to comment on the performance gains (or losses) you may experience from this modification but I bet you can find some muffler alteration info by searching this awesome forum.

[raceman]

actually the mod to muffler you`re suggesting is a feasible one,IF you`re talking about modding the stock muffler from the 84-89 cars or the dual in of the same style.l`ve seen the mod done many times and it works well if done right.A hole is cut on the end of the muffler opposite the stock location(you`re making a symetrical dual out) and with then within the muffler another hole is cut into the baffling.l`ve heard of people cutting the whole thing apart but it`s been established that this is not nessasary.Finally WELD another tailpipe(stock one looks best from a damaged unit) or weld two new exits that match.The other way to do this is welding two additional exits straight out the back,early sport exhaust style.Several on the board have done just that.These rear exits can be capped for street use.l recommend having this work done by a good performance exhaust tech/welder though

[Wil Ferch]

Raceman:
The right-side addition of a stock tip was done to my car..but I would add that the right side hole should be made very small...as small as 1/4-1/2" ( at first)....surrounded by a welded-on tip. Why? If you cut a 1.75" ( or whatever it s stock) hole on the right side, you soon find out that 60-80% of the sound and volume will come out the right side. You may want a balanced approach to this. Then, you can "open up" the hole in progressively larger increments to your satisfaction. In any case, the right and left tips are the same diameter.
---Wil

[JBO]

Wil- if you drill that small a hole, how can you get any baffles out or drill them (which I read is what you are supposed to do to increase the growl, which is what I'm after)?

[911pcars]

Tom Tweed might want venture here and post the sport muffler modification pic (or do a search for ttweed - sport muffler). Basically it's open up the right end of the muffler, then cut an opening in an internal bulkhead; cut a flap at the top and create similar openings in two other bulkheads.

You can use a cutoff tool to create the flap, but for all other operations you'll need the services of a welder and some pipe material - curved for a right side tailpipe and straight, twin pipes for a factory sport muffler look.

Sherwood

[911nut]

I cut my muffler into 3 pieces to take out the glass packing and perforated pipe. I made 2 baffles and welded them into the shells before welding the shells back together.
I did realize a performance gain and the sound is priceless.
Do it!

[ttweed]

Originally posted by 911pcars
Tom Tweed might want venture here and post the sport muffler modification pic

Your wish is my command, Sherwood:


I have only done a single out sport muffler, using this drawing as a basis, but completely removing the slotted pipe section, and for that we cut a large, rectangular hole out of the upper (and inner) portion of the shell in the middle, between the bulkheads.

My understanding is that if you do the twin outlet as shown, the two inner torched openings can be cut and the pieces drawn out thru the two holes you cut for the exhaust pipes. No other access holes are necessary in the outer shell. Cut off the old single outlet, patch the hole up, and you're there.

As most epoxies lose all their wonderful physical properties well before 600F, and your exhaust gas temps can exceed 1000F, using JB Weld is not a good idea. Get a welder at a muffler shop to do it. The last one I had done cost $80.

TT

[Zeke]

As someone pointed out recently, once you cut the holes for the dual outlet pipes sport style, it's a direct shot from the inlet. I see no reason anymore to do any intenal cutting. Maybe that makes it a bit quieter, but it doesn't open it up any more unless I, too, am missing something in that drawing.

Same for the right end pipe mod. That opens the chamber up to the outside and, like Wil says, the gasses are now allowed to exit directly thru the right pipe. Whereas, they still have to go thru the system to get out of the original left pipe.

I think the internal holes cut as shown would be more appropriate for a dual out, side exit unit. BTW, this only applies to dual in mufflers. I have no idea what the flow pattern of the single in muffler looks like. And JBO didn't tell us what he has.

[Wil Ferch]

JBO:
To be clear, the PO did the mod to my car, and it seems that only a right tip was added and *possibly* the right side baffle that is near the very end was burned or drilled through ( mine's an 85 and has this baffle plate near the new right side opening..unlike the flow path for the pre-74 shown by Tom Tweed). If you check this BBS, it's been discussed before, IMHO, if I were to do it myself with what I know now, I would start with a very small new right-side hole to try to flow balance ( sound balance) better....and enlarge step-by-step. As it is, I'm considering adding a "plug" on the right side with a section cut out or a hole drilled. Think doughnut ring with a screw fitment through the tip sidewall.
--Wil

[Steve W]

One of my customers in Finland shared with me his experiment with modifying his stock muffler on his Euro Carrera. Hope he doesn't mind my sharing this info:


Hi Steve,
I`ve opened her up at the right side this evening. 1 1/4 " = 29 mm.
Groooowwwl. Seems to be about equal exhaust flow both sides with this hole,
just a little more at the original outlet. I think I`ll go for this or maybe
1-2 mm or so bigger.

It may be imagination, but i think there`s not much difference in the
"loudness department" inside at 4`th at 100 km/h and without any
resonance/booming.
Feels like it pulls ever so slightly better. Not much, but seems sort of rev
a bit easier. Maybe 3-5 hp above 4000. Little difference below this revs,
but sort of lost some of the lag and pulls more evenly. Sort of awakened
the stock chip a tad.
I dont know what kind of fuel setting that will be appropriate for this
exhaust mod, but maybe a tad less as for a regular "sports-exhaust" ?
Really don`t have a clue Maybe half of the fuel amount you added ?????
You`ll have to decide whats best !


Hi Magnus,
>
> Good to know that the noise in the car is without resonance or boom. Is
the
> sound good or
> does it sound like an exhaust leak?



Hi again Steve,
The sound is somewhere between "good" with a hint of exhaust leak. I will
take it up to a 32 mm hole. I`m going to add some nice 90 mm tips from BOSI.
There wasn`t any shop in Norway that I know of that could deliver the one
from BOSI with a resonator built in. So I`m going to tune this myself making
my own resonator. 2,5" tube with lots of holes maybe with a little "hat" at
the outer end - weld on, slide the nice and shiny 3,5" over and tackweld.
Original outlet is so muted that I think it`s unnecessary with a resonator.
We`ll se. I just I hope that I`m not going into booming/resonating by doing
this. I`ll keep you informed.



Hi Steve,
My new 90 mm exhaust tips look very cool, pointing 45 out and slightly down.
I will post you a pic later.
Opened up to 38 mm, very cool exhaust note but this is to much for my
liking. Too loud and a little booming also. This would have been annoying on
longer trips. Have modified with entering a water-pipe union into the hole
in the muffler that takes the hole down to about 32 mm with the possibility
to blank it off completely if I want to. I think this is very smart ;-)
The sound is better with a slightly bigger hole because the hint of ex leak
sound is now gone. It is though a little odd pfffffffffffffff sound at idle
because the hole with the union now is directed more into the wall of the
tip. And the ex gas slams into the rolled lip of the tip. Should have
drilled the hole a little more backwards. Will modify this at some ore
another way. The rule must be; don`t drill before you know exactly vere the
tip will be placed for best looks.
Cut tips at an 20 degree angle facing directly upwards on the right side tip
and facing three o`clock for the left tip.
It do got some improvement. The lag is substantially less now I`m sure.
Are you aware of the fact that a muffler from a -86 do not have the same
internals/baffles as the older ones. The older ones look like the one you
have poste pics of at the BB. I do recall to have read somewhere that
the -86 had a muffler with 10 percent better flow. It must be caused by this
rearranging of the internals.
I can not read out the whole Porsche part # because my original was so badly
rusted on the outside. I
think the sound is somewhat darker and more mellow on the newer one.
But what the heck, its pretty alright with the older ones too..

Kjetil has finally made up his mind. Your chip is better in many ways, but
this we already know.
You will now have two promotors in Norway, me in the north and one more in
the capitol of Norway, Oslo which is 16500 km south of me and in the region
with the most Porsches in Norway. Yes, we sure have a long country.

If you think my exhaust mod can do with a tad more fuel, please do so.
One/two duty cycles ?
I think so because I can feel difference between the 32 mm hole open vesus
capped off. If You are convinced though, that such a small hole do not do
any leaning them burn it the way You mean its best.

Magnus

[SCWDP911]

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