993_Pilot

Certainly possible, but the original weld quality is crap. The only good reason that I can see not to, is that it may be more difficult to cut them open accurately and you will be cutting through two layers. The end caps of the cans are slip fit before they are welded. It might also make it a bit harder to get everything lined up with all the tack welds before you start to run the bead to seal them up. If you use a Production type wire feed welder, and move along quickly, you could duplicate the crappy welds, but I am not sure why you would want to... Unless you have a concourse quality car and need the stock look, or have an emissions/inspection issue? I cut a bit down, because that is what Robin does with his RSR's and I wasn't sure what I was getting into until I opened them up. It worked well for me and I don't care about the look that much because they can't be seen unless you lay under the car.

993inNC

You did TIG weld those cans back together didn't you Jeff? Not MIG?

993_Pilot

I don't have a TIG welder, even if I did, my skills aren't that great. I paid someone to TIG weld it for me. I'm sure the original welds were done with a MIG... and by someone in a hurry!

993inNC

LOL.....I hear ya. Well at least you had it done right I don't know, but I would imagine that Porsche had someone sitting welding muffs all day. It takes a good hour a piece to do them right, my guess is they aren't made with top quality SS and a quick weld by machine is all thats necessary. I have multiple sets for our doing our (DACH) modified muffs and they all pretty much look the same from the factory.....crappy!

rwestervelt

Hey Jeff

Any update on this front? I am preparing to do an internal LPMM.

-Rick

993_Pilot

I do have an update, but not the one you're looking for. My original intention was to do the same thing with a larger internal LPMM type bypass. What actually happened, was that when I was fitting the pipe for the bypass, I tried to tack it in place with my MIG welder before I took it down to the guy who does all the TIG welding for me. Unfortunately, that was a poor decision, because I blew through the pipe in a few spots and caused a big mess. I should have let him do all the welding. Another lesson learned.

What I ended up doing was a complete internal gutting of the muffler. It has worked well for friends on their motorcycles, so I thought that I would give it a try. I cut the pipes where you see the red lines and discarded everything to the left, and stitched the cans back up. (see picture below) I got the cans done and mounted up on Saturday, but I haven't had a chance to do much driving yet. My impression so far, is that they are a much deeper tone at idle than either stock or my previous mod and they have a bit more volume too, which is exactly what I wanted. As the throttle is opened up I was afraid that these would end up being too loud, but they have ended up about right in tems of volume for me. I wish that I had heard the DACH's, RSR's or LPMM's in different sizes to give you a comparison. I will do a more complete wrte-up one I have had a chance to drive with them a bit more.

rwestervelt

Thanks for the update. Sorry to hear about the MIG blowout. It sounds like you ended up with a good result nevertheless.

-Rick

brucec59

Jeff, it looks like you'll have basically no mufflers at all after this, more like a really big bypass pipe! Hopefully you won't have resonance with that big empty can.

Which makes me wonder, why doesn't someone make something that just connects the cat to the tip directly (as in the red arrow below - Jeff, I hope you don't mind me stealing your pic). I guess that's basically what a supercup muffler is...

What about a simple turn-down pipe at each outlet of the cat? (asside from the fact that it would look terrible)

993_Pilot

No problem with the picture theft. This is a public forum and I put the pictures up for public use and educational reasons.

After I cut out all the internals, I briefly considered installing a 180 degree bend to connect the inlet and outlet, but decided that it would probably be too loud. A turn down straight from the cat could probably be done well enough to not be too ugly and would save quite a bit of weight, but I am sure this would also be way too loud... at least for the street.

You might think there was no "muffling" going on in an empty can, but there definitely is. There is a bit of resonance, but it isn't too bad. There is also a very slight slight burble when under deceleration / engine braking. It isn't a popping like an exhaust leak, but more of a rumble. My current plan is just to live with them for a while before I do anything else. I may eventually do the LPMM to my previously modded cans ... who knows.

This project has been an experiment for me, and I am sure the experimenting will continue.

Miller_arch

One thing about this muffler mod excitement is the price of these things on eBay has gone through the roof!

Akerlie

Jeff,

Did you repack the muffler with fiberglass before you closed it again ?
Or did you leave it empty ?

Best regards

993_Pilot

I left it empty.

Akerlie

Thank you for the quick answer, then i can weld mine tonight.
Thank you for the writeup

993_Pilot

Did you put a bigger bypass in or do anything different? I hope you took a few pictures and post your impression once you've had a chance to hear them.

Akerlie

I followed your method in detail
I do not want the sound level to be to far away from stock.
If I want more sound i can always get a cat bypass, and than easily go back if I am taking the family along for a trip.

When i was polishing my left muffler i noticed that it was pretty beat up, it had several thin cracks and i was really struggling to get it apart. The "seem" on top of the muffler also was starting to open up.
Has anyone seen this on their mufflers ?
Doesn't seem like it has been in a accident or nothing, more like it is just getting old (the car has 65K miles).
I TIG'd the seem but filled the cracks with MIG.
The right hand side muffler was good as new, both are Gillet's stmped with 95/11.

I won't be driving the car until May but i might post a sound clip from the garage before that