[Oktom2]

Hello

My M2 has an Akrapovic 300 cell sport cat paired with the stock exhaust. For some reason, it sounds much quieter than any video I can find online of the same setup. This is something that has been worrying me for a while.

At first I thought that was the way the car is supposed to sound with the stock exhaust, so I bought an Akrapovic Evolution exhaust, installed it but it sounded really quiet (day and night vs videos of the same exhaust). I brought the car to an exhaust installer shop and they confirmed that was not the way it was supposed to sound.

My car had an ECU tune done by the previous owner at a local shop so I thought that maybe the tune was affecting it, so I reverted the tune to stock.(I had plans to go with another tune later on anyways). It did not change anything.

I suspected that something was wrong with the exhaust (broken control kit? broken valve? something stuck inside the line?) so I removed it and put back the stock exhaust which surprisingly sounds a bit louder than the Akrapovic one. Later on I used a small camera to inspect inside the line and could not identify anything blocking the air flow.

Now I am back with the stock exhaust, but when I compare how my car sounds to any video out there of a car with catted downpipes, it really seems quiet. There is very little sound when rev'ing up, mostly engine noise. When rev'ing down it is somehow loud.

After I went back to the stock exhaust I did see a 180001 bad cat error code and I thought that was just the o2 sensors being over sensitive so I just deleted it.

Could it be that I have a clogged cat?! Or could it be something wrong with the turbo?
I didn't want to make this post and tried to find information online but I couldn't find anything close to what I am experiencing.

Before I go to a shop and remove the downpipe for a visual inspection, I would like to hear your opinion on my car exhaust sound. What problem it could be..

I made a quick video, in sport+, with the engine warm, the valves opened and rev'ing up to 6k~7k RPM.

Any opinion will be appreciated.

[Oktom2]

Oh and this is with the Akrapovic Evolution:

Very different than all videos of the same exhaust... :/

BTW my car has no OPF.

[tenkies]

I have an Akra with a AA catted DP and I feel like my car sounds much louder and more aggressive that what your videos show. Changing exhausts shouldn't throw a Cat error. I think it wouldn't hurt to get your Cat checked.

[bmxcamel]

Is the video with stock exhaust after the car is up to operating temperature? I see you said that is sport+ although from sound alone it sounds like comfort mode.

The lack of burbles/pops leads me to think the car is either cold (I don't get pops and burbles until a few min after starting) or not opening the exhaust valves when you switch modes

[gphung]

FWIW OP mentioned on Facebook that it was indeed a clogged Akra catted DP. OP's car had an aggressive burble tune that was passed on from the previous owner.

[AndrewC1989]

Originally Posted by gphung

FWIW OP mentioned on Facebook that it was indeed a clogged Akra catted DP. OP's car had an aggressive burble tune that was passed on from the previous owner.

Thanks for following up. I hate when people ask for help and then leave everyone hanging once it's fixed on their end, as if their solution couldn't help others

[Oktom2]

Hi

I just saw the replies today. Thanks.
I asked on this forum and I got no answer for days, so I took the initiative to remove the cat (the purpose of this post was to get opinions before I decide to spend money on having it inspected), before anyone had posted any reply here. Indeed the sportcat was clogged. That was the reason for the quieter sound.
Last time I checked here, my post had zero reply so I didn't rush to post an update.

Here is a picture of the cat (turbo side) :

[Oktom2]

Originally Posted by bmxcamel

Is the video with stock exhaust after the car is up to operating temperature? I see you said that is sport+ although from sound alone it sounds like comfort mode.

The lack of burbles/pops leads me to think the car is either cold (I don't get pops and burbles until a few min after starting) or not opening the exhaust valves when you switch modes

It was sport+ and the engine was warm (after 1h driving).

[Oktom2]

Originally Posted by tenkies

Changing exhausts shouldn't throw a Cat error.

I also thought so but I am new to this platform and sometimes things are different than what you are used to see. (first bmw here)

[Oktom2]

Originally Posted by AndrewC1989

Thanks for following up. I hate when people ask for help and then leave everyone hanging once it's fixed on their end, as if their solution couldn't help others

Sorry I didn't know everyone was "hanging".

[CalAcacian]

Originally Posted by Oktom2

Hi

I just saw the replies today. Thanks.
I asked on this forum and I got no answer for days, so I took the initiative to remove the cat (the purpose of this post was to get opinions before I decide to spend money on having it inspected), before anyone had posted any reply here. Indeed the sportcat was clogged. That was the reason for the quieter sound.
Last time I checked here, my post had zero reply so I didn't rush to post an update.

Here is a picture of the cat (turbo side) :

wow, that's absolutely terrible. No wonder you weren't getting any noise. You probably took a good hit to power too with that much resistance. Unless you were standing on the limiter for minutes at a time this never should have happened.

[Oktom2]

What I am not sure is why did it shrank like this.
When I google failed cats all the pictures look very different to this. It looks like it was exposed to extreme heat coming from the piping surrounding it. Anyone has experience with this kind of pattern?

[Oktom2]

Originally Posted by CalAcacian

wow, that's absolutely terrible. No wonder you weren't getting any noise. You probably took a good hit to power too with that much resistance. Unless you were standing on the limiter for minutes at a time this never should have happened.

The day before I removed the cat, the car felt like it had less than 200hp.. It felt so slow I knew something was not right (much slower than the day before). It leads me to think that the cat got bad over time, but I almost nevet had any burbles during driving, which is really weird. The previous owner said that he had a burble tune and then reverted it because that was too much burbles. I wonder if the damage was done at that time and then the cat slowly degradated from its bad condition? (not sure if it makes sense)

[CalAcacian]

Originally Posted by Oktom2

The day before I removed the cat, the car felt like it had less than 200hp.. It felt so slow I knew something was not right (much slower than the day before). It leads me to think that the cat got bad over time, but I almost nevet had any burbles during driving, which is really weird. The previous owner said that he had a burble tune and then reverted it because that was too much burbles. I wonder if the damage was done at that time and then the cat slowly degradated from its bad condition? (not sure if it makes sense)

A bad burble tune certainly could cause the cat to experience extreme temps that would cause damage/melting, but I haven't heard of any burble tune I know of for this car having that effect. This is a really strange failure.

[Oktom2]

I could not find any other case of a similar failure until I found this post:
https://f30.bimmerpost.com/forums/sh....php?t=1693551
The shape of the cat material looks very similar to that guy. Kind of shrinked.

[Altra]

Wow that is absolutely wild how clogged the cat got....had no idea they could get this bad!

[AndrewC1989]

Originally Posted by Oktom2

Sorry I didn't know everyone was "hanging".

Sorry if I came off rude. Have a happy holiday.

[cecaa850]

Looks like it's been running rich or mis-firing. Whatever caused it needs to be corrected or it'll ruin the next one.

[CalAcacian]

Originally Posted by cecaa850

Looks like it's been running rich or mis-firing. Whatever caused it needs to be corrected or it'll ruin the next one.

OP mentioned that he reverted the tune to stock after purchasing from the prior owner who had a burble tune on, so there shouldn't be an issue anymore.

This is a good lesson on burble tunes, they can be just fine for 99% of users, but we have to be careful of ramping up the parameters too high and causing issues like this. I can't imagine that having this much heat in the exhaust does a stock turbo any favors either, they aren't designed to handle that much heat.

[tenkies]

Originally Posted by CalAcacian

wow, that's absolutely terrible. No wonder you weren't getting any noise. You probably took a good hit to power too with that much resistance. Unless you were standing on the limiter for minutes at a time this never should have happened.

Whoa...never seen a Cat melt failure like that one. I'm guessing it was a really bad tune. I'd get your turbo checked out as well. All the back pressure and heat...not sure what it'll do the turbo.

[Pray for Mojo]

That's not clogged its melted and completely deformed the cataylst. I'm surprised with all that additional back pressure that the car still ran. Bit worried about your turbo long term now, with all that heat and no where to go.

[CalAcacian]

Originally Posted by Pray for Mojo

That's not clogged its melted and completely deformed the cataylst. I'm surprised with all that additional back pressure that the car still ran. Bit worried about your turbo long term now, with all that heat and no where to go.

It might not be a bad idea to get an oil analysis done. You could be looking at coked oil if the turbo was getting to hot.