Borla exhaust

Thanks Cory, I didnt know how they were attached... I will then look for that option as they look pretty awesome !
maybe wrapping the tips (behind the diffuser) and adding the tips will help even more.
 
I'm pretty sure all that black plate is for is purely aesthetics. It's to prevent light from shining through the exhaust tip from behind and also to cover up the ugly mufflers. The frequency range you're trying to reflect is around 100- 150 Hz and at that range the wavelength is between 9 ft and 11 ft. The sound will go right through that little plate like it's not even there.

The only real way to reduce exhaust drone in an existing exhaust is by putting on a Helmholtz resonator (aka 1/4 wave resonator).

I'd post some great links for you guys but I'm a new member, so I can't... but there's good ones on eng-tips, grassrootsmotorsport, and fastfordmuscle.
 
And it is obvious that these frequency ranges we are hearing that we call drone are probably at the resonant frequency of that area of the car back there and are coupling up to act like a passive radiator in a speaker.
 
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After hearing some improvement by others following their installs, I went ahead applying a sound deadener material into the trunk to see if that would quiet down the exhaust noise in the cabin. I also took some noise level measurements using a decibel meter to try and verify the effectiveness.

I purchased the Noico 80 mil sound deadener mat and the 170 mil sound insulation foam materials. I went with these because I wasn't totally convinced of what the results would be and didn't want to drop the money for something more expensive like Dynamat. Plus, others have done a similar install with reported success.

The install went relatively smoothly, but took a lot more time measuring, adjusting, and rolling than I had anticipated. This was my first time doing any type of sound deadener, but this product was really easy to work with and forgiving if you had to peel it up and reapply into any creases/surfaces. I did manage to tear the foil backing a few times, but it was easily patched up with foil flashing tape. The diamond pattern on the back was helpful in telling the progress areas where you had rolled. All together I would estimate that the total time spent on the install was around 10 hours. I ordered the 18 square foot package of the 80 mil mat and used all but one full sheet and a few remnants. I did not end up using the Noico Green 170 mil sound insulation foam because I wanted to see how the mat itself performed.

Prior to the install of the mat, I took a noise reading using a decibel meter that I rigged up in the front passenger seat about where someone's head would rest. My measurement run consisted of driving down the local surface streets using a "normal for me" right foot and then going one exit down the highway (~1.5 miles) trying to get the revs up. I started out (surface -> hwy) in comfort mode, then exited, turned around and backtracked the same route (hwy -> surface) in sport mode. The car was empty aside from the meter and myself - no radio, minimal AC. The contents of the trunk consisted of the battery, spare tire, jack kit, tire cover, stock carpet pad, cargo tray, and cargo net.

Test before deadener:
  • Comfort mode, surface streets (~45 mph @ 2k RPM) to Hwy (~90 mph @ 4.5k RPM) = 84 dB max
  • Sport mode, Hwy to surface streets (similar speeds) = 82.3 dB max
Interesting reading, but it did confirm my suspicion that comfort mode seemed louder. My guess is that the car's desire to keep the RPMs relatively low (1.5-2.5k) create more of a resonating rumble when pulling off.

Test after 80 mil deadener:
  • Comfort mode, surface streets to Hwy = 81.3 dB max
  • Sport mode, Hwy to surface streets = 82 dB max
Conclusion: The mat installation definitely reduced the loudness of the in-cabin noise from the exhaust. The decibel meter recorded an overall drop of around 3 dB in comfort mode. Not sure about the frequency difference, but resonance of the exhaust system in the cabin of the car is definitely improved over not having the mat installed. In my opinion the noise is definitely reduced, but you can absolutely still hear the Borla exhaust. On a recent road trip, a highway "drone" was present when cruising (~2k RPM) but negligible; normal conversation wasn't an issue and the radio would have easily drowned it out. Following these results, I may try installing the foam insulation mat around the trunk areas and on the underside of the stock carpet pad. Overall, I would say that I am happy with the results.

Check out the images below for more details on my install and setup:

The decibel meter set up on a tripod inside the cabin near the passenger headrest.
1kkMAuE.jpg


Post install images:
sZv9PgH.jpg

sMkxXDD.jpg


Also, for kicks, I set up my GoPro to record a time-lapse of the install:
 
Just installed the borla...

I keep forgetting I’m fat and older than I once was. Didn’t have jack stands so only used race ramps on the rear tires.

It wasn’t fun. Took a slow 4 hours starting at 8:30 am. Didn’t have breakfast.

Atlanta’s heat index while I did it was 95 degrees.

I’m exhausted. Lol

Hard to get leverage on old bolts without elbow room. Lots of PB blaster last night helped. Would have taken double without that.

Someone suggested taking the rear rubber hanger bracket off... I feel it is mandatory. Once you have the mufflers in the bracket, you can’t slide it back enough to connect to the pipes with HFC (or resonators... not sure what they are technically).

Anyway... startup was arousing. Yes. That is the right word.

Loud but if you are smart about gear and throttle input, you won’t piss of the PoPo.

So far, no drone. Well engineered. Everything lines up perfect.

I have pre-install decibel measurements below. Will post soon the post install data.
69C4B5CB-3047-401E-870C-C77E3B2CADB1.webp 1B7D9259-38DE-49BE-BE23-CD33FE2573A4.webp 2A2E359F-1F54-4AC1-8DEB-50417FF3C068.webp

You also need a 19mm socket.
 
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Max dB stock


4 hours sitting

Exterior Startup:78.9

Exterior Rev:91.5

Interior Startup:65.1

Interior rev:73.0

Interior idle:41.2


Overnight sitting

Exterior Startup:82.4

Exterior Rev:97.7

Interior Startup:65.3

Interior rev:72.1

Interior idle: 43.1

Outside idle:70.9


Normal sitting

Exterior Startup:78.7

Exterior Rev:90.3

Interior Startup:66.2

Interior rev:69.7

Interior idle: 41.9


Driving (in sport mode)

82.6 interior win up driving wot

86.3 interior win down driving wot

66.6 interior win up driving normal acceleration

60.3 interior win up driving cruising

73.6 interior win down driving normal acceleration

72.3 interior win down cruising
 
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Just curious, did you have any trouble getting to the top nuts all the way at the front? I have a cordless impact drive and used a 15" extension to get to those. I had all four wheels on jack stands and it wasn't much easier. I was exhausted after the 2-2.5 hours of this install. BTW, I installed the Thermal unit but same thing basically.
 
Just curious, did you have any trouble getting to the top nuts all the way at the front? I have a cordless impact drive and used a 15" extension to get to those. I had all four wheels on jack stands and it wasn't much easier. I was exhausted after the 2-2.5 hours of this install. BTW, I installed the Thermal unit but same thing basically.
I did have difficulties. I had bought extensions as suggested (you or someone else... can’t recall)... amazon shipped wrong one. So Did it the old fashioned way with normal 19mm box wrench and a BFH. Once it budged, switched to my 1/2 socket and 19mm and cranked it in small amounts since the x pipes were in the way. It sucked.

I don’t own an impact gun. Will be on my list along with proper 1/4 | 1/2 extensions.

Also, I didn’t have enough room to use my long throw torque wrench. So I just cranked them down as much as one can at those angles using standard 1/2 sockets.

I’ll check them in a week and re-crank if needed.
 
I love my cordless impact wrench. If you wrench on your car enough it is surely worth it. Especially if you are like me and getting older and easy to wear out!
 
Max dB stock


4 hours sitting

Exterior Startup:78.9

Exterior Rev:91.5

Interior Startup:65.1

Interior rev:73.0

Interior idle:41.2


Overnight sitting

Exterior Startup:82.4

Exterior Rev:97.7

Interior Startup:65.3

Interior rev:72.1

Interior idle: 43.1

Outside idle:70.9


Normal sitting

Exterior Startup:78.7

Exterior Rev:90.3

Interior Startup:66.2

Interior rev:69.7

Interior idle: 41.9


Driving (in sport mode)

82.6 interior win up driving wot

86.3 interior win down driving wot

66.6 interior win up driving normal acceleration

60.3 interior win up driving cruising

73.6 interior win down driving normal acceleration

72.3 interior win down cruising

Quick clarification. What "weighting" did you use when you took these measurements? Did you use "A" or "C"?
 
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From interior to exterior to high performance - everything you need for your Stinger awaits you...
Rynil2000 - Which dB weighting did you use when you took your measurements? "A" or "C"? Also, did you turn off the in-cabin Exhaust Sound enhancer when you ran your tests?
 
Quick clarification. What "weighting" did you use when you took these measurements? Did you use "A" or "C"?
I have no idea what you mean by a or c.

I’m using a $30 decimal meeting from amazon. I’m sure it is +/- 5 dB accurate.

This isn’t for others to know EXACTLY how loud it is. It’s for me to know the approximate delta between the old and new in similar settings.

This isn’t a pure scientific experiment.

And augmented engine sound on my 18 can only be set to minimal. Not off. And that might only work on custom. Startup by default is eco or custom and doesn’t really matter.

Road tests were done in sport.

I’ll post the final results soon (tonight).

But for example. If old cold rev external was 91 dB, it just registered as 116 if I recall.

Generally speaking, In some conditions it will gain 20-30 dB higher. Others exactly the same as stock. But the tone change is the dramatic figure. And I swear downshifts/revs are much quicker. Might be my imagination. We’ll see.
 
I have no idea what you mean by a or c.

dB is a pure measure of sound pressure.

dB(A) and dB(C) are "weighted" measures, designed to give more weight to the sound pressures generated in the range that humans can actually hear. dB(C) is weighted towards higher frequencies in the human-audible range than dB(A).

I’m using a $30 decimal meeting from amazon. I’m sure it is +/- 5 dB accurate.

An increase of 3dB is a doubling of sound pressure. An increase of roughly 10dB is required for a human to perceive the sound as twice as loud.

+/- 5dB accuracy isn't great - it means that a two sounds could give the same dB reading even if one sounds twice as loud to a human.

But all is not lost - read on. :)

This isn’t for others to know EXACTLY how loud it is. It’s for me to know the approximate delta between the old and new in similar settings.

This isn’t a pure scientific experiment.

The conditions for such an experiment would be beyond most of our capabilities to out together I suspect. What you're doing is perfectly valid though, within the constraints of the gear you've got!

And augmented engine sound on my 18 can only be set to minimal. Not off. And that might only work on custom. Startup by default is eco or custom and doesn’t really matter.

Something something stupid "augmented engine sound" crap. I wish car manufacturers would stop this stupid shit.

Road tests were done in sport.

I’ll post the final results soon (tonight).

But for example. If old cold rev external was 91 dB, it just registered as 116 if I recall.

Generally speaking, In some conditions it will gain 20-30 dB higher. Others exactly the same as stock. But the tone change is the dramatic figure. And I swear downshifts/revs are much quicker. Might be my imagination. We’ll see.

The more often you repeat the experiment, the more data you'll have, and the better you'll be able to adjust your reading of the data to help remove the error factor in the equipment - you can remove outlying results and come up with a sample set that can give you something that better reflects what you hear - as you said, what you hear is the most important thing here, the absolutely values aren't as important.
 
I have no idea what you mean by a or c.

I’m using a $30 decimal meeting from amazon. I’m sure it is +/- 5 dB accurate.
The weighting button is the "C/A" button just below the "On/Off" button on your meter. As Manaz already described, it applies somewhat of a filter to the overall measurement. The "A" weighting will filter out the lower and higher frequencies. The "C" weighting will be more flat. Since the exhaust is usually in the lower frequency range, an "A" weighting will probably show a much lower dB level than the "C" weighting because the "A" weighting will filter it out.

And augmented engine sound on my 18 can only be set to minimal. Not off. And that might only work on custom. Startup by default is eco or custom and doesn’t really matter.
I'm just curious because in my '19 I can turn it "Off" in the Advanced Settings and wanted to know how much that effect the dB meter was picking up.
 
The weighting button is the "C/A" button just below the "On/Off" button on your meter. As Manaz already described, it applies somewhat of a filter to the overall measurement. The "A" weighting will filter out the lower and higher frequencies. The "C" weighting will be more flat. Since the exhaust is usually in the lower frequency range, an "A" weighting will probably show a much lower dB level than the "C" weighting because the "A" weighting will filter it out.


I'm just curious because in my '19 I can turn it "Off" in the Advanced Settings and wanted to know how much that effect the dB meter was picking up.
All measurements were “a”.

I’m not redoing them.

Enjoy.
6CAF6156-5144-46CB-9316-93EC93D7FD66.webp
 
From interior to exterior to high performance - everything you need for your Stinger awaits you...
Rynil2000 - Which dB weighting did you use when you took your measurements? "A" or "C"? Also, did you turn off the in-cabin Exhaust Sound enhancer when you ran your tests?
I'm told by my engineers, of whom I borrowed the meter, that it defaults to A - so A. I was only using the max dB feature at the time. The "in-cabin exhaust sound enhancer" was never on. The Borla is plenty loud on its own :)

I would be interested in seeing a frequency curve; just for kicks. So if anyone has an app to recommend? :coffee:
 
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Just curious how are you guys turning off the sound enhancer? I cannot find a setting anywhere but three volume levels it can be set on for the custom driving mode.
 
Just curious how are you guys turning off the sound enhancer? I cannot find a setting anywhere but three volume levels it can be set on for the custom driving mode.
On my 2019 GT1, I hit the Setup button, then go to Vehicle, then Active Engine Sound... my options are Off, Minimized, Normal and Enhanced.
 
All measurements were “a”.

I’m not redoing them.

Enjoy.
View attachment 27943
“A” is good and most representative of the human ear.

I wasn’t asking you to redo them, just was curious as to what you used so I could better interpret your results.

Good work!
 
On my 2019 GT1, I hit the Setup button, then go to Vehicle, then Active Engine Sound... my options are Off, Minimized, Normal and Enhanced.

I guess 2018 is not there.
 
From interior to exterior to high performance - everything you need for your Stinger awaits you...
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