DIY: The 135 Muffler Innards Mod

[mechanicalmagic]

I was going to mod the inside of the 135i muffler for a bit more sound.

Here's the story:
http://home.comcast.net/~david.johns...MWMuffler.html

Dave J.

[EspressoBoy]

hmmm can you post a before and after sound clip?

*grin*

EspressoBoy

PS
I had to ask...... I just had to.
I am also a pirate! But not sure how long more.... (see flag)
I don't make a very good pirate... I drink too much espresso and not enough rum.

[mechanicalmagic]

If I put it back together, sure.
I'm still trying to decide what to do.

Dave J.

[jtsherri]

Doing this makes the exhaust sound quite a bit more aggressive than stock. Based on the pics, I'm not sure it'll offer much more performance; however I have heard the result of 2x cars with this done and it sounds great.

[BlackjackMulligan]

Originally Posted by mechanicalmagic

I was going to mod the inside of the 135i muffler for a bit more sound.

Here's the story:
http://home.comcast.net/~david.johnson11/BMWMuffler.html

Dave J.

aww man you gotta weld it back up and see how it sounds now!

[mechanicalmagic]

OK, I'll put it back together, and give it a go.

Suggestions on the proper way to provide good sound clips would be appreciated.

I do have a DB sound meter, not sure if the still/mov camera has sound, and I don't think SHE will let me put HER laptop and webcam outside. (SHE is rather cautious when it comes to HER computer.)

DJ

[Addict...Nah Im A Junkie!]

At "Pull that glass out of there, time for the real fun." on the site it looks like you scalped an AARP member!!!

[mechanicalmagic]

Originally Posted by Addict...Nah Im A Junkie!

At "Pull that glass out of there, time for the real fun." on the site it looks like you scalped an AARP member!!!

Thank you for the compliment. As an AARP member, for quite a while, I wish my hair looked that young, or had that much.

<on old guy memory>
One of my heros in the 60's was an old guy. He had a repair shop in Fresno, for sports cars, last name was Cardwell. He was in his 70's, and drove a Cobra. In those days it was like American Grafitti, drag races from one light to the next. The cops knew him, knew he was not going to do anything stupid, never got a ticket. But he, and his wife, with her little scarf were out EVERY Saturday night. Taking on all comers, from one light, to the next. Never lost.

He was out autocrossing several times, but there was no competition.
</on old guy memory>

DJ

[bman6074]

subscribed. I am interested in hearing the before and after. Nice job on cuting it open and explaining how things are wokring. Unfortunatly I can't add any help as i dont' know enough about the flow in a muffler.

[BlackjackMulligan]

Originally Posted by mechanicalmagic

Thank you for the compliment. As an AARP member, for quite a while, I wish my hair looked that young, or had that much.

<on old guy memory>
One of my heros in the 60's was an old guy. He had a repair shop in Fresno, for sports cars, last name was Cardwell. He was in his 70's, and drove a Cobra. In those days it was like American Grafitti, drag races from one light to the next. The cops knew him, knew he was not going to do anything stupid, never got a ticket. But he, and his wife, with her little scarf were out EVERY Saturday night. Taking on all comers, from one light, to the next. Never lost.

He was out autocrossing several times, but there was no competition.
</on old guy memory>

DJ

ahhhhh sounds like good times. Unfortunately I grew up in the early 90's when a Beretta GT was considered a "hot rod"

[mkPOTO]

subscribed for soundclip

[Addict...Nah Im A Junkie!]

AARP was stuck in my head because I have been looking up my mothers benefits for her over the past week. Lol. I always wanted grey hair when I was little, as it comes in I still like it.

[Gogud]

I am glad someone has decided to have a go at the stock muffler. I think about it every time I open the shed and step over the damn thing. Since I have the replacement installed, there is no burning need to get on it. From the photos of the inside, it appears that improvement will require experimentation. Flow improvement should be as important as increased sound level. Mechanicalmagic, if you haven't already welded yours up, you may want to consider the following:

The primary chamber with packing may impact sound levels only and the latter stages may yield better results. What I envision is something like this:

1) Design some sort of inexpensive flow meter to gauge the restriction and changes. A fairly high volume air sourch is needed. You may have or can borrow a dust collection blower--1hp motor connected to a fan with a 4" outlet. Other possibilities are a leaf blower, A/C blower, or a compressor with a large hose. Neck down to outlet to the size of the muffler inlet. Add a vertical clear plastic tube just before the muffler. The tube dia. should be just large enough for a ping pong ball to easily move inside and be longer than thought necessary to allow fine tuning. The size of the inlet hole and if necessary an outlet hole at the top will be determined by how the system reacts.

2) Take a reading with the stock muffler.

3) Cut and modify the innards.

4) Replace the cut panels and seal with duct tape, 3M putty tape, or whatever you have that works.

5) Take readings, reopen and try different mods, and compare results.

6) If possible, try the modded muffler on the car before welding it up. Use hi temp muffler patch tape, hi temp silicone, or some combination of things. If you warm the car up before switching and only run it long enough afterward to get a good sound recording, you may be able to get away with materials that don't do well at high temps. When satisfied, weld it.

There are some unknowns that might make the whole effort worthless. Will the air source produce enough flow? Will the tube/ball be sensitive enough to indicate the differences? I am guessing that commonly available mechanical pressure gauges and shielding gas flow gauges are not sensitive at the pressures involved. Perhaps a flow bench will work but who has access to one?

[pondo]

I'd use a golf ball in a clear 1.5" PVC pipe. I think the diameters are perfect from the days i made a golf ball cannon in high school (hair spray propellant, gas grill sparker for an igniter and a golf ball launched into the clouds).

Necking down a leaf blower could be difficult though and they provide quite a lot of CFM air.

[Zirenz2006]

that glass wool looks like someone stuffed a gray wig in there

[mechanicalmagic]

Originally Posted by Gogud

Mechanicalmagic, if you haven't already welded yours up, you may want to consider the following:

The primary chamber with packing may impact sound levels only and the latter stages may yield better results. What I envision is something like this:

1) Design some sort of inexpensive flow meter to gauge the restriction and changes. A fairly high volume air sourch is needed. You may have or can borrow a dust collection blower--1hp motor connected to a fan with a 4" outlet. Other possibilities are a leaf blower, A/C blower, or a compressor with a large hose. Neck down to outlet to the size of the muffler inlet. Add a vertical clear plastic tube just before the muffler. The tube dia. should be just large enough for a ping pong ball to easily move inside and be longer than thought necessary to allow fine tuning. The size of the inlet hole and if necessary an outlet hole at the top will be determined by how the system reacts.

2) Take a reading with the stock muffler.

3) Cut and modify the innards.

4) Replace the cut panels and seal with duct tape, 3M putty tape, or whatever you have that works.

5) Take readings, reopen and try different mods, and compare results.

6) If possible, try the modded muffler on the car before welding it up. Use hi temp muffler patch tape, hi temp silicone, or some combination of things. If you warm the car up before switching and only run it long enough afterward to get a good sound recording, you may be able to get away with materials that don't do well at high temps. When satisfied, weld it.

Well, you are about 3 hours too late. Welded it up this morning.

I did TRY to setup a flow bench. I used my 1.5 hp shop vac blower motor. The three inch output fits into the input flange very nicely. I also got out a Dyer Pressure gauge (0-1" of water) with at least 100 increments. My first attempt using some rubber hose was just great. .26" pressure with the valve open, .96" with the valve closed. Then I tried to duplicate the test. Got negative pressure all the time (Venturi effect). So I tried all sorts of other ways to sample the pressure. No luck, got frustrated, F&#$ it.

As an aside, with the shop vac motor running full blast, there was VERY little air coming out of the gaping holes. I could have used toilet paper to cover the holes, wet on the edges to hold it in place.

I could have built a rotameter flowmeter, but didn't think about it. And after looking inside the muffler, I don't think there's any good way to reduce the restrictions, on a stock muffler.

OK, if you were to cut the entire top, and bottom off, leaving just a band to hold things together, then you could cut off the top pipe, and fab a longer radius "S" pipe. weld it in. Then cut out the lower pipe, and fab a new one. Then weld up all the holes. I pondered filling the holes, but the access from the top only made it a no-go.

(But that sort of defeats the purpose, it can be seen. As in "But officer, look it's got the stock muffler. BMW part numbers, look here".)

And, for you sound nuts. I spent this morning trying to figure out how to get some sound clips, given what I got. (I even had to resort to RTFM on the camera.) My sound skills are not yet proven.

And again, any suggestions on how to get a GOOD sound clip?

[mechanicalmagic]

OK, I got the resonator on and did my best at some sound. Not my best work.

Click the third line:

"Goto the Second Part of the story"
for the details.

I will be at some GGC BMWCCA events, car #223, Cashmere SIlver 135i.

Dave J

[PrimoM3]

Nice job. Would be great if you could make a table of your findings with each setting - stock, golf tee and hairless. Include the decibel reading at idle, 1000 rpm steady, 3000 rpm steady, etc. I'd also inlcude a notes section for each where you could include your personal thoughts and impressions.

Again, nice work.

[mechanicalmagic]

Originally Posted by Primo135

Would be great if you could make a table of your findings with each setting - stock, golf tee and hairless. Include the decibel reading at idle, 1000 rpm steady, 3000 rpm steady, etc. I'd also inlcude a notes section for each where you could include your personal thoughts and impressions.

I thought about that. But, even slamming the throttle to the floor didn't give me what I wanted, was not repeatable. And without the car under load, it was not representative of the real world.

To do this right, I would need a chase car, with a GOOD microphone, or a track situation. Don't got it.

If anybody has a good comparison vehicle, in the SF Bay area, I'm ready to do a side by side. I'm not happy with my sound clips, but I don't know how to make them better. I'm not going to do another swap just to make another useless sound file.

More suggestions Please.

Dave J.

[blklacker]

Soo golf T myth does work