MPE buzz at 1500rpms

[CeeTeeX5]

Hi All,

Now that it's getting in to windows down season, I'm noticing a slight metallic buzzing sound at around 1500 rpms that seems to be caused by the exhaust resonance frequency at that RPM. It's noticeable when the vehicle is cold and seems to go away after the car/exhaust have warmed up. I notice it when the rpms drift over 1500rpms in each gear as I'm acceleration. It's mostly noticeable in eco mode and sometimes in comfort mode. I'm thinking this is mainly because you're generally in the low RPM range in those two modes when driving casually.

It almost sounds like the heatshield around the exhaust is vibrating against something causing that metallic buzzing but I can't seem to put my finger on it.

Has anyone noticed this or have this issue? Any ideas on how to narrow down the sound?

I'm thinking about just buying some dynamat and sticking it to the heatshield to see if that makes any difference.

[menelaos]

Have noticed some throttle issues at low rpms too, eco and comfort modes.
I keep my windows closed 24/7, 365 days and music is on, so it's tough to catch those sounds.
Will open window and test case you described and report back.

[CeeTeeX5]

Well, I don't think noise in my situation is actually coming directly from the exhaust. Not sure what throttle issues you are having but I haven't noticed any throttle issues with the MPE. Are you referring to sound or throttle response?

[Hashtag]

I have MPE + MPPK and don't notice anything like that at 1500rpms. The only thing at that speeds is popping

[menelaos]

Originally Posted by CeeTeeX5

Well, I don't think noise in my situation is actually coming directly from the exhaust. Not sure what throttle issues you are having but I haven't noticed any throttle issues with the MPE. Are you referring to sound or throttle response?

Responses, I think that valve on the rear right had a role to play.
Nothing major, I just don't think the throttle response is the same as it used to be; could be the BMS intake too.
Another member reported similar issue with ACS exhaust.

Update: took it for ride, rolled down windows, nothing from the rear.

[CeeTeeX5]

Originally Posted by menelaos

Responses, I think that valve on the rear right had a role to play.
Nothing major, I just don't think the throttle response is the same as it used to be; could be the BMS intake too.
Another member reported similar issue with ACS exhaust.

Update: took it for ride, rolled down windows, nothing from the rear.

Cool, thanks for checking

[Violator]

Originally Posted by Hashtag

I have MPE + MPPK and don't notice anything like that at 1500rpms. The only thing at that speeds is popping

+1
Hope you get it figured out

[Hashtag]

Originally Posted by Violator

+1
Hope you get it figured out

I assume it's the crackling popping, and burbling from the MPPK +MPE. I hear it from time to time when I'm in bumper to bumper traffic. It's pretty faint for the most part and I drive with the windows up 99% of the time. Is the popping not normal or should I be looking into this ?

[Violator]

Originally Posted by Hashtag

I assume it's the crackling popping, and burbling from the MPPK +MPE. I hear it from time to time when I'm in bumper to bumper traffic. It's pretty faint for the most part and I drive with the windows up 99% of the time. Is the popping not normal or should I be looking into this ?

Oh no, it’s normal, mine is always popping and burbling. I drive mostly in Sport or Sport+.

[BeeMdblU]

Originally Posted by Violator

Oh no, it’s normal, mine is always popping and burbling. I drive mostly in Sport or Sport+.

how do I get more of that?

[Kzang]

Originally Posted by Hashtag

I assume it's the crackling popping, and burbling from the MPPK +MPE. I hear it from time to time when I'm in bumper to bumper traffic. It's pretty faint for the most part and I drive with the windows up 99% of the time. Is the popping not normal or should I be looking into this ?

That's 100% normal. I think Violator was saying hope you figure it out to the op.

[Violator]

Originally Posted by BeeMdblU

how do I get more of that?

Make sure you have the MPE and MPPk, put it in Sport and let it rip.

[menelaos]

Just wondering: could it be the tip clamps have loosen up?
Mine are welded, so not sure if this is what's causing it for you.

[CeeTeeX5]

It’s not the clamps. I checked the connections when I had the car on a lift installing the lip. I’m ordering some sound dampening self adhesive sheeting to stick to the heatshield above the exhaust to see if that killz that buzzing.

It’s completely gone after the exhaust has warmed up and the exhaust tone has changed.

[Violator]

Originally Posted by CeeTeeX5

It’s not the clamps. I checked the connections when I had the car on a lift installing the lip. I’m ordering some sound dampening self adhesive sheeting to stick to the heatshield above the exhaust to see if that killz that buzzing.

It’s completely gone after the exhaust has warmed up and the exhaust tone has changed.

That sounds like it could be internal. Have you taken it back to BMW for a look?

[menelaos]

Did they weld the exhaust to the downpipe, or just used clamp?
My guy did it for "insurance".

[menelaos]

Originally Posted by Violator

That sounds like it could be internal. Have you taken it back to BMW for a look?

You mean something in the exhaust chamber going awry?

[CeeTeeX5]

Originally Posted by Violator

That sounds like it could be internal. Have you taken it back to BMW for a look?

I haven’t since they didn’t install it. If the sound dampening stuff doesn’t solve it I might take it in.

[r33_RGSport]

@CeeTeeX5 , check the tip.
I start noticing BMW MPE tips are cheaply made.
I am on my 2nd set of tip on my G30 540i MPE.
Starting to rattle again.

[CeeTeeX5]

Originally Posted by r33_RGSport

@CeeTeeX5 , check the tip.
I start noticing BMW MPE tips are cheaply made.
I am on my 2nd set of tip on my G30 540i MPE.
Starting to rattle again.

Oh interesting. I’ll check the tips too.

[LocksmithNick]

If it’s the tips, maybe powder coat them? The extra thickness might help dampen the rattle just enough.

[CeeTeeX5]

Originally Posted by LocksmithNick

If it’s the tips, maybe powder coat them? The extra thickness might help dampen the rattle just enough.

The tips are actually already powdercoated. I did push on the outer finisher "cap" of the tips a bit and they do have some very slight play against the inner portion. I might put a bead of silicon sealant along that inside edge where the outer cap and the inner sleeve meet.

On that note, I was really trying to focus on the sound today and noticed it kind of sounds like metal vibrating against plastic which is why I'm leaning towards the heat shielding or potentially something in the bumper vibrating.