[Wizper_F32]

I have a strange turbine sound coming from the engine bay of my F32 2015 435i (n55) when decelerating. It sounds like a helicopter just after it turns its engines off. The noise starts at around 30mph 2,000rpm and is most audible when I’m slowing to a stop.
I tried to record a video/audio file of the sound but it’s hard to hear. U can hear it best at the beginning of the video and the last few seconds at the end of the video.
I’ve read other posts where they are having the same issue but there are no conclusions to what it is. Most of them are saying it’s an alternator pulley and I’ve read others saying it’s a bearing in the transmission.
I recently installed a plumb back turbosmart BOV and I’m concerned that the sound is my turbo being stressed/failing.
Any input would be helpful. I’m going to grab a scanner and try and get some codes read. My JB4 is saying it cannot successfully display codes right now and I’m stressing out. Let me know what u think the sound is please. Thanks,
- Wiz

https://youtube.com/shorts/S8kywG2p3...IQ3TFIAqTyFA5M

[LuxoM3]

I'm going to guess regenerative braking. It's engaging and charging the system.
(Me, 2015 435i with 80k miles).

If you want to experiment with it NOT being on... try turning off the auto start/stop feature (little button under the Start/Stop Engine button) and then the next time you come to a stop, shift into neutral and hold the car at the stop in neutral versus using the brake and leaving it in drive. Shift back into drive when the light turns green.

[Wizper_F32]

Originally Posted by LuxoM3

I'm going to guess regenerative braking. It's engaging and charging the system.
(Me, 2015 435i with 80k miles).

If you want to experiment with it NOT being on... try turning off the auto start/stop feature (little button under the Start/Stop Engine button) and then the next time you come to a stop, shift into neutral and hold the car at the stop in neutral versus using the brake and leaving it in drive. Shift back into drive when the light turns green.

It’s still making the noise. It almost seems louder today. My JB4 isn’t successfully generating any codes. I feel blind.
I looked under the the front end today and noticed some oil around the charge pipe. I’m convinced that my turbo is going. I’m concerned it failed because of the turbosmart BOV being installed in the incorrect orientation. Does anyone know if this is facing the correct direction? The cables to the actuator are facing down and to the left. The plum back is facing up/slightly to the right.

[LuxoM3]

Oil seepage around the charge-pipe isn't that end of world and there isn't anything mechanical in the charge pipe to make noise.

Blow-off valve, stock or not, it's a valve with a simple motor, so nothing dramatic enough to make noise loud enough to be heard.

OK so when trouble shooting, try to stick with the original problem without going down too many rabbit holes.

"I have a strange turbine sound coming from the engine bay of my F32 2015 435i (n55) when decelerating. It sounds like a helicopter just after it turns its engines off. The noise starts at around 30mph 2,000rpm and is most audible when I’m slowing to a stop."

There's only so many things that can make noise on deceleration:
1. brakes - because you are braking
2. transmission / driveline
3. alternator - when these are dying, you can hear the bearing and/or they don't charge the system...

How many miles on your car? Automatic or stick?
And are you specifically doing anything like braking or downshifting when this noise occurs?

[Wizper_F32]

It’s my turbo. I did some research on the sound and it’s dead on. I stopped driving it since it has gotten progressively worse. My F32 has 89k. I’m just going to go stage 2 pure and verify the VR9’s orientation simultaneously. The noise occurred after 30mph initially, but I could hear it best while slowing to a stop. It didn’t matter if I downshifted or not. It consistently made a turbine sound as I slowed to a stop once it started. My transmission is an auto.

[LuxoM3]

Wizper_F32:

I agree with you, but thinking it's NOT your turbo.

I was shaving this morning and thought about your post some more. I had an old turbo kit from GReddy for my Miata years ago and that kit was like a stage 1 without a blow-off valve. So whenever I got off boost, I'd get this whirring sound because the boost pressure had no where to go. Once I got the upgraded BOV, sound went away.

"I recently installed a plumb back turbosmart BOV"

Given this is literally your own change, I highly suggest pulling the new Turbo Smart valve off and putting your stock one back on first before thinking it's the turbo. It's a quick, cheap and easy first diagnostic step.

Good luck man!

[Wizper_F32]

I’ll definitely throw it back on real quick. Couldn’t hurt to check, right? I’m pretty certain based off of the performance of the car and the intensity of the sound, that no matter what caused the issue; this turbo is blown. And the BOV is the last thing I have installed so I am guessing that is what caused it. But it could be that I pushed my tune too hard, I don’t know. I’m having my mechanic take a look at it next week to make sure I’m fixing the actual issue and find any other issues I’m oblivious to. I will keep u posted with what his diagnosis is. I appreciate ur input and helping me figure this out. I have checked a bunch of posts about this exact same issue and no one has ever posted the conclusion to what the source of the issue was.