[rjd_F30]

Current Standings:



Hey everyone,

So BunkerJ Noelified and myself talked about starting a volume comparison thread for different exhaust setups for the N20/N26 a while back. This is that thread The idea came about when Noel mentioned that his catless + AWE setup was far too loud for his taste, and I was surprised, because I have what I would've imagined to be a similar setup, catless + MPE, and find it to be fairly tame, and only loud when you want it to be (perhaps a trade between us is in order). So we thought it would be a good idea to start a thread that will act as a collection of objective tests that measures the loudness of different setups, so anyone deciding on what they want for their N20/N26's loudness can use this as a resource. Hopefully we'll get a good collection of data on different variations of catted and catless and all the different cat-back setups so people can know how loud their setup will be before they buy.

Now, for the sake of accessibility and simplicity, I decided to use a mobile app that uses a phone's microphone to measure decibel ratings. While it will probably be slightly less accurate than a high-grade decibel meter (although app store reviews say it's just as good), it will get close. So, I'll start.

App used: Decibel X: dB, dBA Noise Meter
Phone used: iPhone 7

I enoucrage everyone else who participates to use the same app for more consistency. The same phone would be ideal too, but that's not as realistic...

Testing method:
(results below)

Both idle decibel rating and a sport mode rev to 6,500 rpm were measured. Oil temp was at 205° on the nose, so the car was warmed up in case that has any impact on how loud the exhaust will be.

Idle (sport mode; flap open): Phone was placed on the ground exactly 3 feet away from exhaust tips, screen up, with microphone side closest to exhaust outlet. Record the idle for at least 10 seconds. The car was at normal idle speed with A/C off.

Rev (sport mode; flap open): Phone was placed on the ground exactly 3 feet away from exhaust tips, screen up, with microphone side closest to exhaust outlet. Foot to the floor rev to 6,500 rpm.

So anyone else who decides to participate, try to emulate the above testing method as best as you can.

Results:
(Anyone who participates feel free to delete my data/info and use this as a template to share your own.)

Car: 2013 328i
Engine: N20
Exhaust setup: Catless downpipe, stock N20 mid pipe, M Performance Exhaust
Average Decibel Level at Idle: 81.8 dB
Peak Decibel Level reached for rev to 6,500rpm: 113.8 dB



So you'll notice that I reported the average for idle, and peak for the rev, just thought that made the most sense. Do share the graph Decibel X generates if you can though, just so we get the full picture.

Ok there ya go! I know we've got at least BunkerJ and Noelified as 2 more entries, but the more the merrier! If you're interested, feel free to share what you got and see how your setup stacks up against others. Hopefully this'll be helpful to people deciding on an exhaust setup.

P.S. If you're running a burble tune and your car gunshots like I know many catless cars do, make sure to report the peak of the actual rev, not the gunshot that may confound that peak reading. My car didn't pop like it sometimes does while I was measuring, but I'm sure that will be a consideration for some.

[sspade]

Great thread. Really interested in the results and may participate. Ill have a catless downpipe with stock N26 mid pipe and muffler installed this weekend barring anything crazy going wrong. Not sure where Ill need to go from there but hopefully this thread will help me decide.

Honest question(s):

Is it good to rev your car to 6500rpm with no load and also, what is the factory rev limiter set at (and is yours removed)?

[rjd_F30]

Originally Posted by sspade

Great thread. Really interested in the results and may participate. Ill have a catless downpipe with stock N26 mid pipe and muffler installed this weekend barring anything crazy going wrong. Not sure where Ill need to go from there but hopefully this thread will help me decide.

Honest question(s):

Is it good to rev your car to 6500rpm with no load and also, what is the factory rev limiter set at (and is yours removed)?

Nice, that's exactly what I started it for. Hopefully this thread will help you decide, and feel free to participate both before and after you install your downpipe. It would be cool to have data on a stock car (exhaust wise) as well for a baseline.

Bringing the car to 6500rpm whether stationary or while driving is not harmful if done in moderation. I wouldn't sit in park and bang it off the limiter, but high rpms are not harmful in moderation. Yes, my car has the stock rev limiter and/or redline. Redline I think is 6900rpm or thereabouts, and the rev limiter is probably about the same, but I'm not 100% sure.

[Noelified]

Awesome thread. I can't wait to do a my control tests and post.

I don't want to make this sound confusing, because it's not and I think this will be an awesome thread to help people decide on an exhaust setup. However, I do want to point out, we need to keep in mind the Decibel Scale going into this. It's a logarithmic scale, far from a linear scale. The relative loudness we perceive cannot be objectively measured. Most people will perceive a sound to be twice as loud as another when they are about 10dB apart. Where 0dB is the quietest sound a healthy human ear can hear (not complete silence), and every increase of 3dB represents doubling of the sound intensity (Acoustic power). For instance something 60dB will sound twice as loud as 50dB. Yet that 10dB represents 10x increase of intensity. In this example, you would need to combine 10 of the 50dB devices together to register 60dB (meaning 10 of them would not register 500dB).

Here is an example of the scaling factor:
You can see something registering 80dB sounds twice as loud as 70dB but 4x as loud as a 60dB sound.

Once we start posting our data points, it will make much more sense comparatively.

[bheng89]

Interesting thread. Looking forward to seeing some other numbers!

[BunkerJ]

Originally Posted by sspade

Honest question(s):

Is it good to rev your car to 6500rpm with no load and also, what is the factory rev limiter set at (and is yours removed)?

If your car is warmed up, then it's fine. On top of that, no load means less stress. Just don't bang it at 7k and I'm sure she'll love it.

I should have time after work today to get this going. I found the same app as you. Just need to find an area where someone isn't going to get mad at me.

[Noelified]

Originally Posted by BunkerJ

I should have time after work today to get this going. I found the same app as you. Just need to find an area where someone isn't going to get mad at me.

I know what you mean, I had the same setup. I won't be surprised if you are above 120dB on the revs if you manage it without the gunshot pops.

I did a quick check this morning heading out to work. Cold start idle averaged 108dB and thats with a stock cat.

[BunkerJ]

Originally Posted by Noelified

I know what you mean, I had the same setup. I won't be surprised if you are above 120dB on the revs if you manage it without the gunshot pops.

I did a quick check this morning heading out to work. Cold start idle averaged 108dB and thats with a stock cat.

And that's why I have my cold start removed.

[rjd_F30]

Originally Posted by BunkerJ

If your car is warmed up, then it's fine. On top of that, no load means less stress. Just don't bang it at 7k and I'm sure she'll love it.

I should have time after work today to get this going. I found the same app as you. Just need to find an area where someone isn't going to get mad at me.

I had the same issue lol. I'm sure we'll learn that your car is louder than mine pretty soon, but I still couldn't do this in my neighborhood lol. The back lot of an abandoned Walmart in my area did the trick though, perfect place for car shenanigans.

Originally Posted by Noelified

I know what you mean, I had the same setup. I won't be surprised if you are above 120dB on the revs if you manage it without the gunshot pops.

I did a quick check this morning heading out to work. Cold start idle averaged 108dB and thats with a stock cat.

108dB on the cold start with a stock cat Really interested to see your normal idle and rev readings.

[rjd_F30]

Originally Posted by bheng89

Interesting thread. Looking forward to seeing some other numbers!

Me too! Feel free to make a stock cat MPE entry

[Noelified]

Car: 2016 428ix
Engine: N26
Exhaust setup: Stock cat downpipe, AWE resonated mid pipe, AWE axle-back exhaust. (AWE cat-back Exhaust Suite)
Tune: Stock
Average Decibel Level at Idle (Eco): 93.1dB
Average Decibel Level at Idle (Sport): 92.8dB
Peak Decibel Level reached for rev to 6,500rpm (Sport): 112.7dB




FWIW, I didn't save the report but cold start idle in Eco averaged 108dB. I'll record again in morning and add to this post.

[rjd_F30]

Originally Posted by Noelified

Car: 2016 428ix
Engine: N26
Exhaust setup: Stock cat downpipe, AWE resonated mid pipe, AWE axle-back exhaust. (AWE cat-back Exhaust Suite)
Tune: Stock
Average Decibel Level at Idle (Eco): 93.1dB
Average Decibel Level at Idle (Sport): 92.8dB
Peak Decibel Level reached for rev to 6,500rpm (Sport): 112.7dB

Attachment 1915747
Attachment 1915748
Attachment 1915749
FWIW, I didn't save the report but cold start idle in Eco averaged 108dB. I'll record again in morning and add to this post.

Nice! Thanks for taking the time and posting results. So to analyze (and see if I understand how dB works): because a 10 dB increase is perceived as 2x louder than something else, and my car at revving is 1 dB louder than yours, my car is 10% louder? Is that right? And by the same logic, since your idle is 3.8 dB louder than mine (in eco), it's 38% louder, still hinged on the fact that 10db is 2x as loud (perceptively, not by actual intensity).

EDIT: Ok, I now see that what I said is incorrect. I'm gonna do some reading on the decibel scale, and hopefully when I'm done I'll be able to make a chart that lists what % louder each setup is than stock. Might have to have a chat with one of my physics professors.

EDIT 2: nvm I was right (for the most part) lol

[Noelified]

Originally Posted by rjdnyy224

Nice! Thanks for taking the time and posting results. So to analyze (and see if I understand how dB works): because a 10 dB increase is perceived as 2x louder than something else, and my car at revving is 1 dB louder than yours, my car is 10% louder? Is that right? And by the same logic, since your idle is 3.8 dB louder than mine (in eco), it's 38% louder, still hinged on the fact that 10db is 2x as loud (perceptively, not by actual intensity).

Yeah, I would say that's right in a way, at least as close as a comparative "loudness" as we can get.

[Noelified]

Originally Posted by rjdnyy224

Nice! Thanks for taking the time and posting results. So to analyze (and see if I understand how dB works): because a 10 dB increase is perceived as 2x louder than something else, and my car at revving is 1 dB louder than yours, my car is 10% louder? Is that right? And by the same logic, since your idle is 3.8 dB louder than mine (in eco), it's 38% louder, still hinged on the fact that 10db is 2x as loud (perceptively, not by actual intensity).

EDIT: Ok, I now see that what I said is incorrect. I'm gonna do some reading on the decibel scale, and hopefully when I'm done I'll be able to make a chart that lists what % louder each setup is than stock. Might have to have a chat with one of my physics professors.

I think we can look at it this way. For idle, I'm at say 93dB (rounded) you're at 89dB -- thats about 4dB so I'm 40% closer to twice as loud (perceived loudness).

[McQueen2014]

Great idea to designate a baseline for everyone to test with but you forgot a couple of variables that can make a lot of difference.

1. Distance to a reflective source... I.e. a wall or ceiling, other vehicles, people standing around watching you test.

Someone doing this in a single car garage (door open presumably) would likely get a higher reading than someone in the middle of 40 acres of freshly mown grass.

Maybe add in a stipulation to be in an open parking lot with no vehicles near the rear of the vehicle that are closer than 3 spaces beside or 2 rows away directly behind.


2. The mic on you phone isn't very directional so ambient will augment any readings as well (1+2=2.1 and all that). So testing near the local AF base while F16 or C-17s are taking off, might be a bit skewed... Perhaps a baseline pre-test ambient wouldn't be a bad idea either...

Oh man... I gotta get out more...

[rjd_F30]

Originally Posted by Noelified

I think we can look at it this way. For idle, I'm at say 93dB (rounded) you're at 89dB -- thats about 4dB so I'm 40% closer to twice as loud (perceived loudness).

Ok got it, so I was right, at least principally. I was going to ask where we go after 10dB louder mark or 2x as loud, but I found this calculator and general explanation pretty helpful: http://www.sengpielaudio.com/calculator-levelchange.htm. If you scroll down a bit there's some calculators and stuff that is pretty helpful...

Anyway now that that's out of the way, and I kinda get how to use dB comparitvely, I'm gonna make a chart so that no one else has to bother doing the research I did lol. We just need some data from a stock car and then I'll get the chart started.

Also, pretty surprised by your results! A 4 dB increase in idle volume is pretty significant, something one would notice for sure at least. But then it's a bit quieter than catless + MPE on the revs, not by much but a bit quieter nonetheless. Really interesting... Proves that AWE is in fact pretty damn loud. I'm excited to see what AWE and catless registers, and maybe I'll understand why you said it was too loud.

[rjd_F30]

Originally Posted by McQueen2014

Great idea to designate a baseline for everyone to test with but you forgot a couple of variables that can make a lot of difference.

1. Distance to a reflective source... I.e. a wall or ceiling, other vehicles, people standing around watching you test.

Someone doing this in a single car garage (door open presumably) would likely get a higher reading than someone in the middle of 40 acres of freshly mown grass.

Maybe add in a stipulation to be in an open parking lot with no vehicles near the rear of the vehicle that are closer than 3 spaces beside or 2 rows away directly behind.


2. The mic on you phone isn't very directional so ambient will augment any readings as well (1+2=2.1 and all that). So testing near the local AF base while F16 or C-17s are taking off, might be a bit skewed... Perhaps a baseline pre-test ambient wouldn't be a bad idea either...

Oh man... I gotta get out more...

Very good point. Don't collect your data in a parking garage, crowded lot, side alley, or anywhere else it could be skewed by amplification and reflection. Point 2 is also true, but unless ambient is louder than your car which is very unlikely, it shouldn't matter. But worth pointing out

[Noelified]

Originally Posted by McQueen2014

Great idea to designate a baseline for everyone to test with but you forgot a couple of variables that can make a lot of difference.

1. Distance to a reflective source... I.e. a wall or ceiling, other vehicles, people standing around watching you test.

Someone doing this in a single car garage (door open presumably) would likely get a higher reading than someone in the middle of 40 acres of freshly mown grass.

Maybe add in a stipulation to be in an open parking lot with no vehicles near the rear of the vehicle that are closer than 3 spaces beside or 2 rows away directly behind.


2. The mic on you phone isn't very directional so ambient will augment any readings as well (1+2=2.1 and all that). So testing near the local AF base while F16 or C-17s are taking off, might be a bit skewed... Perhaps a baseline pre-test ambient wouldn't be a bad idea either...

Oh man... I gotta get out more...

All good points. My fault for assuming anyone should know not to test in a closed garage, or car wash bay etc. And you're right, ambient sound can add to the reading even if presumably immeasurable. Maybe once the car is in position we record an ambient reading before starting the car. Not that we would do any subtracting or anything but it would give visibility to the test environment.

In regards to holding the phone 12in from the exhaust tips, I'll run a few different tests with surfaces both absorptive and reflective to see if it alters the reading much.

[Noelified]

Originally Posted by rjdnyy224

Ok got it, so I was right, at least principally. I was going to ask where we go after 10dB louder mark or 2x as loud, but I found this calculator and general explanation pretty helpful: http://www.sengpielaudio.com/calculator-levelchange.htm. If you scroll down a bit there's some calculators and stuff that is pretty helpful!

Anyway now that that's out of the way, and I kinda get how to use dB comparitvely, I'm gonna make a chart so that no one else has to bother doing the research I did lol. We just need some data from a stock car and then I'll get the chart started.

Great site you found, I like their charts at the bottom too. Could be helpful.
I also found this chart in the Decibel X app, helps give perspective.

Originally Posted by rjdnyy224

Also, pretty surprised by your results! A 4 dB increase in idle volume is pretty significant, something one would notice for sure at least. But then it's a bit quieter than catless + MPE on the revs, not by much but a bit quieter nonetheless. Really interesting... Proves that AWE is in fact pretty damn loud. I'm excited to see what AWE and catless registers, and maybe I'll understand why you said it was too loud.

Yeah, I think this really helps in a way to remove each individuals idea of "loud" when asking about different setups. I mean, I may say 110dB is too loud and someone else might say they love it, but at least we know its 110dB. Very interesting my idle is that much louder with stock cat but revs, pretty close. This does go to show AWE really did their R&D with our specific engines and what kind of sound most want out of it. I wish I could have dropped the $$ on their switchback system.

Ha ha, Yeah BunkerJ needs to get his setup tested, I'm curious to see the numbers.

[rjd_F30]

A quick note to everyone: notice that the testing method for the idle rating has changed. Noelified brought up some discrepancies with my original readings, and so we decided to change the idle testing method to what is now specified in the OP. That is: phone on the ground exactly 3ft from the exhaust tips, screen up, microphone towards exhaust tips and in sport mode. Rev testing method is unchanged. I updated my results accordingly

[sspade]

N26, stock exhaust.

(Dont mind the shuffling around at the end of clip, forgot to hit pause).

[rjd_F30]

Originally Posted by sspade

N26, stock exhaust.

(Dont mind the shuffling around at the end of clip, forgot to hit pause).

Nice, thank you. Is that a rev to 6500rpm in sport mode (just to be clear)? And I'm assuming that first blip is the rev? That shuffling at the end looks pretty close to the first blip, I just want to make sure it's not confounding. Your stock baseline is going to serve as the hinge that we use measure how loud everything else is over stock, so it's pretty important and I want to make sure I got it right . Would you mind getting an idle (a/c off, 3ft back from tips) reading as well? Thanks!