Exhaust Issue

MDuckie · 11-01-2023, 08:16 PM

Hey all.

I have a DCT M2CS. Two months ago I had the Akrapovic slip on and link pipe installed. About a month in (100-150ish miles?) after a long driving session, the first real lengthy drive with the exhaust, I noticed that there was an odd noise coming from the exhaust at around 2000 rpm, maybe upwards of 3000 rpm under casual exceleratipn. Initially I thought it only happened going from first to second gear in auto mode. It sounds like a resonance/buzz/rattle that can last half a second long or reverberate three consecutive times within 2 seconds. At first I thought it was a valve and that it was being caused by the valve closing and possibly being loose (my valves still behave like the stock system). The valves randomly close at 2k/3k and then reopen at a bit higher rpm.

Fast forward to now with about ~300 miles on it and a couple trips to the shop that installed it, it seems to be coming from the down pipe/flex area right before the link pipe. At this point I can also now replicate it pretty easily after warming the engine/exhaust up at the same rpm (2k/3k) at really any gear. Still at a casual throttle/load. It seems like it’s doing it a lot more after heat cycles but it could be because I’ve been trying to replicate it over and over for the last 100 miles. It may be related to heat cycles?.

I’m not sure what to think or what to do. Is it a normal noise? Did it always make that noise and I didn’t hear it because I still had the second cat? If so, is my down pipe defective? It’s really weird that the noise presented itself right after I replaced the exhaust but the shop says it’s not the exhaust or installation.

Oh and by the way, I think my warranty ends in a little over two weeks.

Hopefully someone has some experienced this before or has helpful insights.

The sound while driving is very obvious but this is what we figured it might be once we got it on the lift:

:
https://youtu.be/oXtb1MHfNjE?si=-yzVpn51rTxRxbb8

It sounds like a more prolonged version of that while under actual load. If that sounds like a normal noise then it’s not what’s causing it. I’m not well versed in all of this.

QM · 11-01-2023, 08:26 PM

I suggest you open a warranty claim through your Akra dealer. I had a faulty valve in my Akrapovic exhaust. I sent in videos and photos per Akra’s request. Once they confirmed the diagnosis, Akrapoivic sent a new exhaust to the shop and paid for reinstall. The shop mailed the original exhaust back to Akra. This process takes time.

Beenz · 11-01-2023, 08:30 PM

I can’t speak from direct personal experience on my CS specifically, but I do know of some others who had installation teething issues. If you thumb through the forum exhaust discussions you will see a few, it seems like most have eventually gone with a full system.

Not saying your installer is deliberately trying to be dodgy but the facts are that it’s only an issue after installation AND the noise is right near where alterations were done. For eg they accidentally bent the DP a little bit and now it rubs/rattles…? Or damage within the Cat?

I have experienced an installer damaging the guts of a hi-flow cat on installation. It was really irritating because the only way to fix it was cut the pipes off and start again.

Jimjamz · 11-01-2023, 10:25 PM

I initially went with an AA straight midpipe with the Akra slip on. I was getting fumes in the cabin and the droning was not good. I removed the link pipe and reverted to stock and all was good with the remaining Akra slip on. I put it down to poor fitting of the AA and Akra systems.

(K) · 11-10-2023, 12:40 AM

This is going to sound stupid but have you checked the tips for pebbles?

I had a similar issue with rattles on my Akra system (M2C) and it *sounded* like it was coming from the downpipe area while driving. I reactively condemned the heat shields and even went as far as thinking it was the wastegate but the car was too new for that to make sense. I went out and put the car on the QuickJack, started tapping on the exhaust with the car off, cold, and traced it back to the rear. Ultimately it lead me to the carbon fiber tips. Sure enough, there were small pebbles wedged between the carbon fiber sleeve and titanium pipes. I got to picking with some pick tools and removed all the errant pebbles. The car was quiet again ever since.

gmhl10 · 11-10-2023, 04:26 PM

Try getting a rubber mallet and start lightly banging around your exhaust area to replicate the sound from underneath the car.

11-01-2023, 08:16 PM	#1
MDuckie Private 93 Rep 70 Posts Drives: M2CS Join Date: May 2018 Location: CT iTrader: (0)	Hey all. I have a DCT M2CS. Two months ago I had the Akrapovic slip on and link pipe installed. About a month in (100-150ish miles?) after a long driving session, the first real lengthy drive with the exhaust, I noticed that there was an odd noise coming from the exhaust at around 2000 rpm, maybe upwards of 3000 rpm under casual exceleratipn. Initially I thought it only happened going from first to second gear in auto mode. It sounds like a resonance/buzz/rattle that can last half a second long or reverberate three consecutive times within 2 seconds. At first I thought it was a valve and that it was being caused by the valve closing and possibly being loose (my valves still behave like the stock system). The valves randomly close at 2k/3k and then reopen at a bit higher rpm. Fast forward to now with about ~300 miles on it and a couple trips to the shop that installed it, it seems to be coming from the down pipe/flex area right before the link pipe. At this point I can also now replicate it pretty easily after warming the engine/exhaust up at the same rpm (2k/3k) at really any gear. Still at a casual throttle/load. It seems like it’s doing it a lot more after heat cycles but it could be because I’ve been trying to replicate it over and over for the last 100 miles. It may be related to heat cycles?. I’m not sure what to think or what to do. Is it a normal noise? Did it always make that noise and I didn’t hear it because I still had the second cat? If so, is my down pipe defective? It’s really weird that the noise presented itself right after I replaced the exhaust but the shop says it’s not the exhaust or installation. Oh and by the way, I think my warranty ends in a little over two weeks. Hopefully someone has some experienced this before or has helpful insights. The sound while driving is very obvious but this is what we figured it might be once we got it on the lift: : https://youtu.be/oXtb1MHfNjE?si=-yzVpn51rTxRxbb8 It sounds like a more prolonged version of that while under actual load. If that sounds like a normal noise then it’s not what’s causing it. I’m not well versed in all of this.
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11-01-2023, 08:26 PM	#2
QM First Lieutenant 287 Rep 312 Posts Drives: 2020 M2CS 6MT Join Date: Oct 2015 Location: Illinois iTrader: (2)	I suggest you open a warranty claim through your Akra dealer. I had a faulty valve in my Akrapovic exhaust. I sent in videos and photos per Akra’s request. Once they confirmed the diagnosis, Akrapoivic sent a new exhaust to the shop and paid for reinstall. The shop mailed the original exhaust back to Akra. This process takes time.
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11-01-2023, 08:30 PM	#3
Beenz Private First Class 153 Rep 161 Posts Drives: M2CS Join Date: Aug 2020 Location: Aus iTrader: (0)	I can’t speak from direct personal experience on my CS specifically, but I do know of some others who had installation teething issues. If you thumb through the forum exhaust discussions you will see a few, it seems like most have eventually gone with a full system. Not saying your installer is deliberately trying to be dodgy but the facts are that it’s only an issue after installation AND the noise is right near where alterations were done. For eg they accidentally bent the DP a little bit and now it rubs/rattles…? Or damage within the Cat? I have experienced an installer damaging the guts of a hi-flow cat on installation. It was really irritating because the only way to fix it was cut the pipes off and start again.
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11-01-2023, 10:25 PM	#4
Jimjamz Colonel 4582 Rep 2,203 Posts Drives: G81 M3 Touring (Frozen Black) Join Date: Dec 2012 Location: Australia iTrader: (0) Garage List 2023 BMW G81 M3 Tou ... [8.00]	I initially went with an AA straight midpipe with the Akra slip on. I was getting fumes in the cabin and the droning was not good. I removed the link pipe and reverted to stock and all was good with the remaining Akra slip on. I put it down to poor fitting of the AA and Akra systems.
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11-10-2023, 12:40 AM	#5
(K) Captain 1278 Rep 837 Posts Drives: '21 M2C 6MT (R.I.P.) Join Date: Jan 2021 Location: Massachusetts, USA iTrader: (6)	This is going to sound stupid but have you checked the tips for pebbles? I had a similar issue with rattles on my Akra system (M2C) and it sounded like it was coming from the downpipe area while driving. I reactively condemned the heat shields and even went as far as thinking it was the wastegate but the car was too new for that to make sense. I went out and put the car on the QuickJack, started tapping on the exhaust with the car off, cold, and traced it back to the rear. Ultimately it lead me to the carbon fiber tips. Sure enough, there were small pebbles wedged between the carbon fiber sleeve and titanium pipes. I got to picking with some pick tools and removed all the errant pebbles. The car was quiet again ever since.
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11-10-2023, 04:26 PM	#6
gmhl10 First Lieutenant 385 Rep 367 Posts Drives: Not a M2 CS Join Date: Feb 2020 Location: Austin, TX iTrader: (0)	Try getting a rubber mallet and start lightly banging around your exhaust area to replicate the sound from underneath the car.
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