Fluttering noise on cold starts (new maddad mids) Video

[whitebimmer09]

So I have my new mid pipes and exhaust (maddad) and now I notice that on cold starts it sounds like fluttering noises by the bottom of the engine (By the stock dps). I brought it back to my exhaust guy and there are no leaks, if this a common noise with the mid pipes? I saw something on the 1M stuff but no real answer.

I still have stock turbos and I'm hoping its waste gate rattle but I don't thing that's it. Is this just the way it sounds?

It stops making noise after a few minutes.

Any thoughts?

[darkrom]

I don't hear anything like that with my mad dad mids, but stock axle back.

[ShocknAwe]

can you post a vid?

[whitebimmer09]

I tried to post the video here but it won't work right so

You can really hear the sound at :12, it goes away after the cold start procedure stops. I don't know if its waste gate rattle or if that is how our engines sound.

This I think is that noise all our cars make after an exhaust. That back pressure noise. I have not stood behind the car during revs so I can't tell

[Solo_M_Tech]

I've never noticed mine doing that, then again I've heard E9X M3's making the same sound after exhaust work.... Could have something to do with reduced back pressure and the diameter of the pipe. I know maddad uses bigger piping than stock, and if your car is a N54 model, the removal of the secondary cats and resonator would explain the reduced back pressure. Just a possiblitiy

[whitebimmer09]

The second video I think is normal but on the first video at the :12 second mark, that noise seems out of the norm. But who knows with these things.

[Solo_M_Tech]

Switch the midpipes back to stock and see if the noise is still there.... if it is keep looking, if not it's just the mids.

[whitebimmer09]

I sucks that I don't work on my own car, I have to bring it back to my exhaust shop where they installed it. They are really cool its just throwing money at them.

I looked around and fund this video, and it seems to have the same sound.

[quick99si]

It sounds like the WG fluttering to me. To verify, you can have someone start the car (on a COLD engine!) while you stand by the rear turbo ready to put your fingers on the actuator rod. When you hear the noise, try to open/close it manually and see if the sound changes.

[Dackelone]

Originally Posted by quick99si

It sounds like the WG fluttering to me. To verify, you can have someone start the car (on a COLD engine!) while you stand by the rear turbo ready to put your fingers on the actuator rod. When you hear the noise, try to open/close it manually and see if the sound changes.

^^+1. Sounds like it to me too. WG's.

IF you have a N54 you can pull off the vacuum hose behind the pass headlight and the rattle should go away. That would confirm it's your WG's.

[whitebimmer09]

I'm going to play with it tomorrow, I am really hoping that it is my turbos. I am always worried that their warranty is going to run out before they fail. It's funny because I get my mids and something fails. I thing it's been doing this for a bit but I was never able to hear it since it was so muffled.

BMW shouldn't give me a hard time about the mids, right? I can't imagine after all the stuff I read. I don't want to have to switch back ect. Besides I have someone picking the stock mids tomorrow.

[whitebimmer09]

So I took off the vacuum hoses, the first one made no change, but when I unplugged the second one it made much more noise, so I plugged it back in and it was fine

[135Pats]

Sounds like WG flutter to me. Totally normal on cold starts. On my car it can't be noticed in any scenario but a door-open cold start.

[whitebimmer09]

Cool, going to ignore it.