[Sered]

Originally Posted by ConradConrad

So I understand the idea is to go for a PE sound which I have never heard but something comes to mind.

In my old mustang world you had SLP loudmouth series mufflers(resonators)

The louder version was completely flow through
see here for pic

Then you had the quieter more refined loudmouth 2 version
See here for pic

So I wonder if what the speculations are you leave the one perforated pipe,then cut out the little catalytic looking thing and add another perforated pipe and then pack the rest of the open space of the muffler with packing?

That 'catalytic thing' is just a resonator; removing it would probably be bad for sound.

I'm thinking the way to do this is to replace the perforated pipes with solid pipes and keep the same packing inside the muffler.

[NoTempoLimitN54]

Originally Posted by Sered

I'm thinking the way to do this is to replace the perforated pipes with solid pipes and keep the same packing inside the muffler.

What would the packing do if the tubing is solid? The sound waves would not be able to penetrate into the packing and loose energy (high frequency noise). It might dampen the resonance slightly, that would be about it.

That said, if the solid tube mod is effective, an easier way to do it would be to wrap the perforated sections with that heat wrap they sell for headers and tie it off with stainless traps. No cutting/welding needed (except to open the muffler can).

Helmholtz resonators are tuned to specific frequencies. The ports you see on speakers are the same type of resonator. So those resonators are probably tuned to dampen a particular resonant frequency, probably the one that is perceived as "drone".

The "catalytic looking thingy" may be an expansion chamber. That might cause some restriction.

Anyone have any info on the 335is mufflers and how they differ from the stock/PE?

What's a used stock E92 335i exhaust worth?

[TommyLights]

Originally Posted by NoTempoLimitN54

What would the packing do if the tubing is solid? The sound waves would not be able to penetrate into the packing and loose energy (high frequency noise). It might dampen the resonance slightly, that would be about it.

That said, if the solid tube mod is effective, an easier way to do it would be to wrap the perforated sections with that heat wrap they sell for headers and tie it off with stainless traps. No cutting/welding needed (except to open the muffler can).

Helmholtz resonators are tuned to specific frequencies. The ports you see on speakers are the same type of resonator. So those resonators are probably tuned to dampen a particular resonant frequency, probably the one that is perceived as "drone".

The "catalytic looking thingy" may be an expansion chamber. That might cause some restriction.

Anyone have any info on the 335is mufflers and how they differ from the stock/PE?

What's a used stock E92 335i exhaust worth?

A used stock exhaust runs about $100.

[Sered]

Originally Posted by NoTempoLimitN54

What would the packing do if the tubing is solid? The sound waves would not be able to penetrate into the packing and loose energy (high frequency noise). It might dampen the resonance slightly, that would be about it.

Exactly, it becomes a big fat resonator instead of just a pipe with an empty shell (a muffler delete). Muffler deletes sound terrible.

Originally Posted by NoTempoLimitN54

That said, if the solid tube mod is effective, an easier way to do it would be to wrap the perforated sections with that heat wrap they sell for headers and tie it off with stainless traps. No cutting/welding needed (except to open the muffler can).

Would that be cheaper than a simple cut/weld? I haven't looked up the costs of header wrap in a long time but I do remember it being expensive. Your idea would also make the mod reversible. Interesting.

Originally Posted by NoTempoLimitN54

Helmholtz resonators are tuned to specific frequencies. The ports you see on speakers are the same type of resonator. So those resonators are probably tuned to dampen a particular resonant frequency, probably the one that is perceived as "drone".

Yup. I was looking at making a set for cat-replacements. The equations for a Helmholtz design are easy enough, it's just a matter of finding the frequency you want to remove. 370z ARK pipes do this same thing and are VERY effective.

[StevenY.]

^ If we can do muffler delete with heat wrap, it seems like it would be much cheaper than a muffler delete. I see some that are $15 for 15 feet whereas a muffler delete costs around $1xx? Someone want to try? Would be interesting since some people don't mind drone from a muffler delete. Also the fact that it would be easily reversible instead of getting the muffler welded back on is nice.

[elim11]

Originally Posted by StevenY.

^ If we can do muffler delete with heat wrap, it seems like it would be much cheaper than a muffler delete. I see some that are $15 for 15 feet whereas a muffler delete costs around $1xx? Someone want to try? Would be interesting since some people don't mind drone from a muffler delete. Also the fact that it would be easily reversible instead of getting the muffler welded back on is nice.

Reversibility, you are correct. Cost, I don't think so. You have to cut the muffler open and then weld it. It seems more time consuming than just a regular muffler delete

[Beemw335]

First step should be removing half the packing materiel and rewelding it back. Im sure thats the is exhaust.
Pe, probably wrap half the perforated pipe and leave other half unwraped + remove some packing.

[StevenY.]

Originally Posted by elim11

Reversibility, you are correct. Cost, I don't think so. You have to cut the muffler open and then weld it. It seems more time consuming than just a regular muffler delete

True, I completely forgot about rewelding the muffler back.

@beemw335 don't think anyone has mentioned half perforated and half covered, could be on to something unless they have already factored that out.

[e92oholic]

Originally Posted by e92ben

Actually I just got the car back from dealer for wastegate & turbos..
So I had to reschedule with the shop Saturday 7:30 am. It's gonna happen lol I'm making sure of this. Saturday afternoon I'm gonna make a full new thread on this

what happened to the new thread....

[DrAmazing]

^^^ this.
Maybe he was on to something and BMW had him taken care of before he could tell everyone that a PE is just an OEM with less stuffing and a few less holes.

[TommyLights]

Based on my own experiment I would have to agree.

[DrAmazing]

Looks like someone could stick a tiny camera on a stick up the back end of a PE and see the perforated pipe from the inside without taking it apart. Maybe even a dentist mirror and a flashlight would do it. Anyone have a spy camera used for looking under doors like splinter cell?

[DrAmazing]

Something like this

[elim11]

Originally Posted by DrAmazing

Looks like someone could stick a tiny camera on a stick up the back end of a PE and see the perforated pipe from the inside without taking it apart. Maybe even a dentist mirror and a flashlight would do it. Anyone have a spy camera used for looking under doors like splinter cell?

Read the earlier post. E60holic got a video scope and confirmed PEhas no holes

[DrAmazing]

Originally Posted by elim11

Read the earlier post. E60holic got a video scope and confirmed PEhas no holes

I thought i had read every page. Good info there.

[e92oholic]

Originally Posted by elim11

Read the earlier post. E60holic got a video scope and confirmed PEhas no holes

nothing visible i could see but i couldnt get all the way in.

[ConradConrad]

OK so then I'm thinking step one is to open it up, wrap the perforated pipes or replace to make it solid, close it up and give it a listen... and move from there

[StevenY.]

Originally Posted by ConradConrad

OK so then I'm thinking step one is to open it up, wrap the perforated pipes or replace to make it solid, close it up and give it a listen... and move from there

Then wouldn't that just be a muffler delete?

[kpjo4]

Originally Posted by StevenY.

Then wouldn't that just be a muffler delete?

no because the muffler packings should still be present.

[Beemw335]

Originally Posted by kpjo4

no because the muffler packings should still be present.

It wouldnt do anything.
Theres holes in the pipe so that the sound could escape and get absorbed by the packing.
No holes= muffler delete. Plain and simple.

[ConradConrad]

Actually thats not right. It would not be a muffler delete.

The pipe goes into the muffler where it forks/splits one end goes into a perforated section of pipe which is the equalizer(connects both mufflers) and the other end goes into the resonator/catalytic looking thing with the packing inside.

Thus enlighten me how only touching the perforated pipe makes a muffler delete?

[Sered]

Originally Posted by Beemw335

It wouldnt do anything.
Theres holes in the pipe so that the sound could escape and get absorbed by the packing.
No holes= muffler delete. Plain and simple.

Yes, it would. Soundwaves, like lightwaves; when absorbed by a medium are then generally re-emitted by that medium as a new source. For soundwaves, this effect is most prevalent in what's commonly called 'droning' and generally requires lower freqs to do it.

So long as the packing is there, it is NOT a muffler delete. Will it be as loud as one? Almost I'm sure, but alot of the nasty rasp and drone that was previously absorbed by the mufflers will still be absorbed, just to a smaller degree.

Furthermore, wrapping the perf pipes with header-wrap will allow some sound through. More than solid pipes.

On topic: I'm still waiting for videos. I ALMOST got this done this weekend, but the gf wanted $600 worth of Halloween/Renn-fair costume and I bought a Kegerator for a party Maybe next weekend. If no one else wants to do this, I'll be doing it by next weekend most likely.