[billypopo]

I’ve got that noise that sounds like i’m being chased by a cop :

2021 M2C sound

Amplitude is somewhat driven by rpm as you can see so that’s why i’m thinking turbos, leak? Or just a bad strap? Car has 18k miles.

[Track/S]

Turbos

[AJAXF1]

i agree turbos. if it were the diff the sound would be more consistent with your speed, not revs. not sure on the cause cuz my exhaust is too loud for me to hear anything.

[AWDtoRWD]

Sorry, I'm new to inline turbos, but what is the potential issue here?

[billypopo]

Originally Posted by AWDtoRWD

Sorry, I'm new to inline turbos, but what is the potential issue here?

Curious to know as well. I’ll obviously bring it to the dealer as it’s still under warranty but it’s always easier when you have an idea of the problem!

[billypopo]

Usual dealership answer : ‘’we can’t hear anything in the video and when we test drove it all we can hear is normal turbo sound’’…

[doughboy]

Could be an auxiliary belt as turbo speed / whine is throttle / boost level related not rpm related.

I.e on a hill more gas means faster turbo but same engine speed.

[doughboy]

Originally Posted by AWDtoRWD

Sorry, I'm new to inline turbos, but what is the potential issue here?

What's an inline turbo? Like a sequential turbo? S55 doesn't have that though. It's a diesel thing.

[Track/S]

Originally Posted by doughboy

Could be an auxiliary belt as turbo speed / whine is throttle / boost level related not rpm related.

I.e on a hill more gas means faster turbo but same engine speed.

The noise is clearly coming from the turbos.

[daap1193]

I have the same noise on my car with DP, is coming from the turbos, some people said its normal, due to the small size of the turbos, I had the same sound on my old 420i when the turbo fail but it came with a low boost error code. usually this noise comes when the turbo gets unbalanced but I dont think is our case because the turbos provide enough boost so they dont trigger any code.

[Track/S]

Originally Posted by daap1193

I have the same noise on my car with DP, is coming from the turbos, some people said its normal, due to the small size of the turbos, I had the same sound on my old 420i when the turbo fail but it came with a low boost error code. usually this noise comes when the turbo gets unbalanced but I dont think is our case because the turbos provide enough boost so they dont trigger any code.

When a turbo is unbalanced it does not throw any error code, it just sounds like the OP.
To give an error it must be broken or wastegate is worn.

[chris719]

Originally Posted by Track/S

When a turbo is unbalanced it does not throw any error code, it just sounds like the OP.
To give an error it must be broken or wastegate is worn.

Is it typically benign for S55, or will these noisy turbos need replacement?

[Track/S]

Originally Posted by chris719

Is it typically benign for S55, or will these noisy turbos need replacement?

It's not the first case I've seen, it should be put in the balancing machine and see the graph. Normally they become unbalanced due to excess rotation.

No need replacement them, can be rebalanced.

[billypopo]

With the car still being under warranty and the dealership saying it’s normal, what you do?

Rebalancing turbos sound expensive, is it?

[Track/S]

Originally Posted by billypopo

With the car still being under warranty and the dealership saying it’s normal, what you do?

Rebalancing turbos sound expensive, is it?

insist and tell them that it is not normal...
It is not expensive I charge 100 euros per unit.

[KevinC]

Originally Posted by billypopo

With the car still being under warranty and the dealership saying it’s normal, what you do?

Find a new dealership, or maybe just a new SA who gives a shit and "gets" it.

When I bought my M2c I sought out a new SA and my dealer has bios for every employee. I found a guy who is an M car enthusiast for ages, currently owns 2, plus a 400 hp Beetle (!) that I can relate to. The dude is awesome and always fun to chat with when I'm in for service. He's the kind of guy who is not going to blow off a problem like this - perhaps OP can find a similar SA?

[bhong]

I have this exact noise. 2020 with 20k miles. Started happening after I got new spark plugs. I'll check back with the shop to make sure they tightened everything properly.