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Really bad drone from new catback exhaust? How to fix?

sauerkraut

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I recall seeing a video on youtube of the fake engine noises without the engine running. The system was in some sort of diagnostic mode, and the fake noises went up and down when the RPM indication changed.

In other words, I don't think the microphone has anything to do with the fake engine noises. I think the engine noises are recorded and played back; the microphone is part of the active noise cancelation system. You have to disable the fake engine noises in the computer.
Correct, the EB has two things going on with this.

ESE = Engine Sound Enhancement
This is the fake engine noise you're referring to and has nothing to do with the microphone.

ANC = Active Noise Cancellation
This is where the rear microphone comes into play. Even the stock exhaust has drone, its just not loud enough to be noticed by 99% of drivers. ANC is listening (the mic) and sending reverse sound waves in order to cancel out the noise and make the cabin quieter. The rear mic is in fact what is listening to do this. The thing is, it was designed with the stock exhaust in mind so its listening for specific frequencies. Once you put on an aftermarket exhaust, those frequencies are totally different. The system still tries to compensate, but is no longer working as well as it should.

TLDR
Disconnecting it does help with aftermarket exhausts.
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lsiunsuex

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Where is the rear microphone in a convertible though?
 

TorqueMan

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The thing is, it was designed with the stock exhaust in mind so its listening for specific frequencies.
My understanding is the ANC system is listening for low frequency sounds between 30Hz and 180Hz that are difficult to attenuate with insulation. The system doesn't distinguish between frequencies in that range; it cancels out (or tries to cancel out) ALL noises--exhaust, engine, wind, road, etc.--recorded by the mic in that frequency range. The system can't do anything about noise outside of that range, including exhaust system drone.

Disconnecting it does help with aftermarket exhausts.
I don't believe disconnecting the microphone will have the desired effect. In fact, you may make things worse because the system is currently attenuating exhaust noise in the frequency range the system works at. If you want to give it a try I'll be interested to hear the results.

If I'm honest, I don't think disabling the fake engine noises will help all that much with exhaust noise either, but it at least has the potential of reducing cabin noise, and perhaps eliminating some resonant frequencies between the fake engine noise and the real exhaust noise.
 

Bull Run

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I recall seeing a video on youtube of the fake engine noises without the engine running. The system was in some sort of diagnostic mode, and the fake noises went up and down when the RPM indication changed.

In other words, I don't think the microphone has anything to do with the fake engine noises. I think the engine noises are recorded and played back; the microphone is part of the active noise cancelation system. You have to disable the fake engine noises in the computer.
+1

Access port uses the tech to show the map selection so if you have AP, turn the car on without starting the engine, and select maps 2 or higher to hear the fake engine noise at given RPM.

I tried disconnecting the rear microphone before and can confirm that it does not disable the fake noises. As [MENTION=31737]TorqueMan[/MENTION] mentioned, only was to turn it and ANC off is via ForScan or equivalent.
 

Bull Run

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As for the drone reduction, I had a large increase in drone between low 1K RPM to low 2K RPM when I switched from my previous setup to my current setup of just one Magnaflow chambered muffler with a single 3" inlet and dual 2.5" outlets (it also acts as a Y pipe).

I heard good things about Vibrant resonators, so I ordered one and had the shop weld it on before the Magnaflow. It made a noticeable reduction in drone, so I'd say it was worth about 4 lbs of net weight gain. Some drone remains, but it's now on par with the differential noise I hear due to aluminum diff busing inserts.
vibrant_resonator.JPG
 

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lsiunsuex

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Alright - so that was NOT the microphone in question, lol... cutting it off neither reduced the noise nor allowed me to talk hands free over carplay, lol...

'need to find the soldering iron now, haha.

Whatever. It's become tolerable. It's growing on me.
1.JPG
2.JPG
 

TorqueMan

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It's become tolerable. It's growing on me.
Did you want to try turning off the fake engine noise? I'd be interested to see if that helps at all. For the record, I don't think it'll make that much difference, but it's pretty easy to do and doesn't cost anything except time.
 
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lsiunsuex

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Did you want to try turning off the fake engine noise? I'd be interested to see if that helps at all. For the record, I don't think it'll make that much difference, but it's pretty easy to do and doesn't cost anything except time.
I will when I place another Amazon order / get a new ODBII adaptor. Whatever crap one I bought last year didn't work with Forscan and I forgot about it after a while. And I haven't met anyone in the area that's into tuning / modifications to borrow one. Even went out looking for performance shops the other day (somewhere local to buy Methanol) and couldn't find anyone. Not much of a crowd here.
 

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sauerkraut

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I don't believe disconnecting the microphone will have the desired effect. In fact, you may make things worse because the system is currently attenuating exhaust noise in the frequency range the system works at. If you want to give it a try I'll be interested to hear the results.
It does work, mine has been disconnected for over a year now; I tested it back then too.

Rear mic plugged in = higher drone.
Rear mic unplugged = still drone due to MBRP Race, but significantly less.
 

MakStang

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^ That
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