[StarMan]

Exterior Sound >

Interior Sound (normal city driving - and me talking for 5 minutes about it) >

Originally Posted by dphjr

Out of curiosity, where did you guys go to get the deletes fabricated? Just a local shop?

Yup just local muffler ship. $150 - $250

Originally Posted by BMW GENIUS

JB4 and FBO, E85, and Map 7 @ 18.5 psi and still nothing lol

i give up. Maybe add some white-lightning or something of that nature

[Mywifes335]

Originally Posted by starvmarv

Exterior Sound >

Interior Sound (normal city driving - and me talking for 5 minutes about it) >

Yup just local muffler ship. $150 - $250



i give up. Maybe add some white-lightning or something of that nature

Is that mild, aluminized or 409 stainless steel? Also what kind of tips are those?

[Mywifes335]

Originally Posted by starvmarv

Exterior Sound >

Interior Sound (normal city driving - and me talking for 5 minutes about it) >

Yup just local muffler ship. $150 - $250



i give up. Maybe add some white-lightning or something of that nature

Uno mas: are you still running a cat?

[StarMan]

Originally Posted by Mywifes335

Is that mild, aluminized or 409 stainless steel? Also what kind of tips are those?

3" pipe (not sure if Mild or Aluminized seeing the pretty much look the same, will need to call the guy up. one just has the extra coating to prevent rust, but it is not Stainless steel) and the tips can be purchased link below (The slant is perfect with our diffuser):

EDIT: They are Aluminized pipes (contacted Muffler shop this morning)

http://www.ebay.com/itm/Stainless-St...-/161205829476

Originally Posted by Mywifes335

Uno mas: are you still running a cat?

Stock Cats and Resonator (only AFE Intake and Muffler delete)

[Mywifes335]

Originally Posted by starvmarv

3" pipe (not sure if Mild or Aluminized seeing the pretty much look the same, will need to call the guy up. one just has the extra coating to prevent rust, but it is not Stainless steel) and the tips can be purchased link below (The slant is perfect with our diffuser):

http://www.ebay.com/itm/Stainless-St...-/161205829476

Sweet. Those tips are a steal.

Are you gonna do a coating on the pipes to stave off rust? I had aluminized and it can rust over time.

[StarMan]

Originally Posted by Mywifes335

Sweet. Those tips are a steal.

Are you gonna do a coating on the pipes to stave off rust? I had aluminized and it can rust over time.

I might as well, i think have a can somewhere in the garage i used for my grill haha

EDIT: Just contacted the muffler shop that did the pipe, they are indeed aluminized pipes

[Mywifes335]

Cool. They'll last a couple years of you keep them salt free.

[StarMan]

About two days of driving, i love the tone and aggressive sound of the car, but the drone at 2500-3300 (mostly present for City driving) is still a bit much for me (i knew i was going to get drone, but didn't thing it was going to get that much).

I have been reading many people doing J-Pipe OR branched off pipe resonators, to reduce drone. I may order http://synapseengineering.pinnacleca...parent=23&pg=1 or have my muffler shop fab one up for me. Seeing that our cars drone more at the 2500-3300 range the pipe will need to be long.

I'll keep you guys posted after results.

[Mywifes335]

Originally Posted by starvmarv

About two days of driving, i love the tone and aggressive sound of the car, but the drone at 2500-3300 (mostly present for City driving) is still a bit much for me (i knew i was going to get drone, but didn't thing it was going to get that much).

I have been reading many people doing J-Pipe OR branched off pipe resonators, to reduce drone. I may order http://synapseengineering.pinnacleca...parent=23&pg=1 or have my muffler shop fab one up for me. Seeing that our cars drone more at the 2500-3300 range the pipe will need to be long.

I'll keep you guys posted after results.

Dude! You are THE MAN. You just saved me the trouble of doing a full bypass. I'm sorry to hear that you gotta go back to the drawing board. One piece of advice from prior experience with my N54 335i...straight through resonators don't really help with drone if you've got it with this setup. You gotta do either a full body muffler with some resonance canceling chamber or a Helmholtz chamber. But this shit is all math.

http://www.performancecarweb.com/showthread.php?t=144

I've got a bypass on the flap side exit (left tip) right now but otherwise running the stock muffler.

Was going to get an m performance muffler used but both being sold were made for the performance diffuser.

Now decided to do the muffler gutting that I originally set out to do but didn't feel like spending ~$300 for just labor.

Seems like the guys who have the muffler delete are ok with drone. I can't...too old.

[StarMan]

Originally Posted by Mywifes335

Dude! You are THE MAN. You just saved me the trouble of doing a full bypass. I'm sorry to hear that you gotta go back to the drawing board. One piece of advice from prior experience with my N54 335i...straight through resonators don't really help with drone if you've got it with this setup. You gotta do either a full body muffler with some resonance canceling chamber or a Helmholtz chamber. But this shit is all math.

http://www.performancecarweb.com/showthread.php?t=144

I've got a bypass on the flap side exit (left tip) right now but otherwise running the stock muffler.

Was going to get an m performance muffler used but both being sold were made for the performance diffuser.

Now decided to do the muffler gutting that I originally set out to do but didn't feel like spending ~$300 for just labor.

Seems like the guys who have the muffler delete are ok with drone. I can't...too old.

Haha, i don't mind loud nor a little bit of drone (my 370z Nismo was loud with little drone and previous M3 had headers, catless, and was very loud when accelerating, but zero drone). I figured i'll try out the muffler delete only, seeing that it doesn't cost much to do in the first place (and easy to go back if i didnt like it). Thing is, the muffler delete on our cars sounds amazing on the outside, i guess our definition of the amount of drone is different compared to others!

The link you sent is the J pipe i was talking about. I'll give it a go, if the drone isn't reduced any I will just sell the muffler delete section (which looks identical to the Fabspeed Muffler Bypass system), accept my loss, and save up my fun money for AWE exhaust in the future.

[Mywifes335]

which M3 did you have? The older ones didn't drone at all. E36s sound amazing.

With the full muffler body exhausts I'm always afraid that they'll sound no better than stock. Inherently, the N54/N55 engines just don't produce a good exhaust sound from the factory. In my opinion they don't sound much like the old naturally aspirated 6s.

I'm getting the muffler gut done next Tuesday and will post results if you're interested.

In speaking with the muffler shop I work with, drone is largely the result of exhaust flow that travels at a low velocity - so you won't hear it at idle (no velocity) and at WOT. Partial load is the worst - the exhaust is "lazy" coming out and the pulses can't get out quick enough. Thus, chambers are where these sound waves go to "die".

[StarMan]

Originally Posted by Mywifes335

which M3 did you have? The older ones didn't drone at all. E36s sound amazing.

With the full muffler body exhausts I'm always afraid that they'll sound no better than stock. Inherently, the N54/N55 engines just don't produce a good exhaust sound from the factory. In my opinion they don't sound much like the old naturally aspirated 6s.

I'm getting the muffler gut done next Tuesday and will post results if you're interested.

In speaking with the muffler shop I work with, drone is largely the result of exhaust flow that travels at a low velocity - so you won't hear it at idle (no velocity) and at WOT. Partial load is the worst - the exhaust is "lazy" coming out and the pulses can't get out quick enough. Thus, chambers are where these sound waves go to "die".

I had e36 M3 ... sounded fantastic. I will be putting stock exhaust back on and save up to get the AWE exhaust. Muffler delete sounds amazing, maybe it was for me 10 years ago, but not anymore.

I may decide to try to branch off a pipe to kill the drone, but we'll see. If not I'll be selling the muffler delete bypass soon with the sleeve adapter so anyone can easily install without having to go to the muffler shop (it'll basically be just like a Fabspeed bypass).

[rainfall]

Not that a lot of people will care, but removing the cat is bad for the environment. It's not just more CO2. There are more toxic stuff that are thrown to the atmosphere.

loud exhausts damage pedestrians' hearing. Again, not that a lot of people will care, but just saying.

https://en.wikipedia.org/wiki/Catalytic_converter

[Mywifes335]

Um......

[StarMan]

I drive my car in manual mode all the time; this is what 10 years of stick shift driving does to you haha. Need to keep my hands busy and feel i am still in control of the shift points.

So i put the car into Comfort "D" mode (can't believe i didn't even try it after delete before) and all of the shift points on normal take off, is right before the more "annoying" drone point. So in city driving, shifting below the 2500 RPM range is great with minimal drone (unless going up a hill or accelerating quick to takeover). Feeling a little better about the delete, but i still think this won't be a long term option.

Haven't decided about the branch off resonator yet.

[Mywifes335]

Originally Posted by starvmarv

I drive my car in manual mode all the time; this is what 10 years of stick shift driving does to you haha. Need to keep my hands busy and feel i am still in control of the shift points.

So i put the car into Comfort "D" mode (can't believe i didn't even try it after delete before) and all of the shift points on normal take off, is right before the more "annoying" drone point. So in city driving, shifting below the 2500 RPM range is great with minimal drone (unless going up a hill or accelerating quick to takeover). Feeling a little better about the delete, but i still think this won't be a long term option.

Haven't decided about the branch off resonator yet.

I'm the same way. But Comfort in D is so frustrating at times. I know personally I can't live with drone but can't live rolling in Comfort D either. Loud I can deal with. I had an Evo with nothing but a resonator and two Agency Power fart cans as exhaust - very loud but no drone. Plus, it shot flames at WOT or lift.

But dude, watch out, don't hurt the environment or deafen pedestrians, OK?

[StarMan]

So I got around doing some calculations for creating a Helmholtz resonator (which is basically a branched off Closed-Pipe resonator or J-Pipe, as it is most commonly known) to reduce or even eliminate specific frequency drone that occurs at a certain RPM (Honda S2000 uses this method in its factory exhaust system to eliminate drone)
**Please note that the method below, will only reduce that certain frequency, so if you want to eliminate the low end drone you’ll still have the drone at the 2500 and above range and vise versa). Basically the sound wave will enter the closed pipe, reach the end, bounce back and cancel out.

The Formula:

[(1125 f\s divided by Hz ) divided by 4] multiplied by 12 = pipe length in inches

1125 f\s – speed of sound in feet per second
Hz – the measured frequency of the drone you want to reduce or eliminate at a certain RPM
4 – the 1\4 wave length
12 – converting it into inches
Pipe length – the length of the pipe that branches out of the stock system

Tools:
You will want to download a frequency counter app on your SmartPhone or tablet. (Having a computer with a good quality mic will give you the best results, but I had none)
You will want a camera or a second person to view the RPM and Frequency (Hz) to determine what frequency you find most annoying at a certain RPM to reduce (this way the driver keeps eyes on the road at all times)

After you have gathered that information plug in the numbers into the formula

At 3300 RPM I was at around 150Hz
At 2500 RPM I was at around 143Hz
At 1500 RPM I was at around 125Hz
*This was using the app. Not sure if it is 100% accurate but it is good enough to give you a rough estimate

For example, if I want to reduce the drone at cruising level I will want to see what RPM I am stable at 50MPH. Say for example 1500RPM.

[(1125f\s ÷ 125hz)÷ 4] x 12 = 27inches

To reduce the drone at 1500RPM you will need to make a 27 inch pipe (closed off at one end) branching out of the exhaust.

The shape of the pipe should’t matter, but most people make a J shape due to space restriction. Some have said closer to the engine will be most effective, others say it does not matter. I had no choice but to do it at the end right before the split to the pipes due to space.

You will want to use the same size pipe for the resonator as your exhaust. (but you should be fine going under half an inch).

Because the pipe is closed off, no air will go in it, therefor performance will not be at all effected. Only the sound waves enter.

MY RESULTS (STILL A WORKING PROGRESS):

I went to my welder guy, and he was able to create the pipe per my specification and I can honestly say I am very happy with the results. There is still the tiniest bit of drone but the reduction is noticeable in the cabin. I feel like I can make it better, but need more trial and error. What I should have done (and what I will do sometime in the next few weeks, is make the J pipe an open, then add a “closed ended” sleeve at the end of it so that I can adjust the length to fine tune it.

I’ll keep you guys posted






(I was going to do a before and after video, but the camera mic isn't the best, so hard to tell the difference. Here is a very short video after J pipe install, driving up a small incline, where drone is most noticeable in these types of set up. As you can tell it isn't at all bad anymore)

Acceleration video:

PLEASE NOTE. I tried my best to get the most accurate information possible above. If you see something that is not accurate, please correct me . I am not responsible for any time, damages, or money wasted trying this mod. It is still a working progress and frequency measurements may be off depending on App\Software and Hardware used (such as microphone quality or an off calibrated measurement system\tool). Please use this guide as a reference only. Thanks.
*I like being the guinea pig sometimes

[Mywifes335]

Bro, above and beyond.

Based on your original experience, I went with the stock muffler mod. We removed all the packing material (enoug to make 2 wigs) and covered the 3rd perforated chamber. The first chamber acts as a place where the exhaust noises go to die.

Result: just a little more sound at idle but noticeably louder at WOT and a hint more straight six sound cruising. So far a bit quiet still.

Going on Saturday to remove the small stock resonator and fit a straight pipe. Also installing the tips you have.

A different approach but hopefully create similar results!

I'll take some pics this weekend and post.

[Mywifes335]

So far, my out of pocket has been $200+. Even after Saturday, the total cost will be about 1/2 the cost of a used M Performance muffler and tips.

[StarMan]

Originally Posted by Mywifes335

So far, my out of pocket has been $200+. Even after Saturday, the total cost will be about 1/2 the cost of a used M Performance muffler and tips.

HA! Same here, i am a bit more satisfied with my muffler delete with the J-Pipe.

Looking forward to your videos.

[Bee Pee]

Marv - as a mechanical engineer with 30 + yrs exp, I never tire of reading/seeing/hearing sound theory being applied in practice.

Originally Posted by starvmarv

Acceleration video:

Your car sounds superb inside as a result of your endeavours.

Great job.

BP

[Mywifes335]

Originally Posted by starvmarv

HA! Same here, i am a bit more satisfied with my muffler delete with the J-Pipe.

Looking forward to your videos.

Marv, with all of your R&D you should totally stake claim to this design. Perhaps even try to "patent" it for the M235i application. No one has a legit muffler delete like this that cancels out drone - at least not to my knowledge.