Loud Mystery "Pig Squeal" sound under hard acceleration

[ajoosten]

I just bought a modified 2009 135i Stage 2+ . I was out doing some 0-60 times for the fun of it, very badly I might say, with a lot of wheel spinning and other things that don’t improve times. After that I noticed that under hard acceleration this very loud pig squeal comes out of the car. It did not happen before my bad driving.

https://youtu.be/ER9MeuRpJ2M

Click the link fr the sound clip. In the clip there is the squeal and then road noise and then a long squeal. I can control the squeal based on pedal placement. I would say about 1/3 pedal depressed where the torque really starts to hit is where the noise starts. If I press the pedal all the way to the floor the sound stops after a while. This may just be me getting out of the power band. It still accelerates but it does not pull as hard as it used to.
I also got a Lean Code on the drive after this noise started to happen.
I have searched YouTube for similar noises but haven’t found this one yet.

Any ideas on what the noise is?

[tomcat0071]

Sounds like your car has a supercharger mate

[SkullV]

Sounds like a boost leak.

[kprocivic]

I'd check the drive belt.

[Jorgensen54]

Good luck! On my last overboosted car, this meant the turbo needs rebuilt/replaced.

[kirill1221]

sounds like a boost leak to me. If we could get a list of all the mods you have under the hood, someone should be able to further assist you.

[ajoosten]

I hope it is a boost leak. I'm going to soap down everything next week to see if I can find anything. I took apart all of the easy stuff last week and did not find it. Any ideas why it won't do it in neutral? Could torque on the drive train cause something to move in the intake system?

VEHICLE:
2009 BMW 135I (N54 engine) 6 Speed
75,000

ENGINE/DRIVETRAIN
BMS N54 Dual Cone
AFE Kidney grill air scoops
Active Autowerk 7” Intercooler
VRSF Charge pipe
Limited Edition HKS SSQ BOV
Cobb Accessport V2
Agency power down pipes and mid pipes (fully catless)
BMS aluminum catch can
BMW Performance Oil Cooler
ACT pressure plate with 6 Puck race clutch
Spec single mass flywheel
BMS CDV
BMW Low Temperature Thermostat

[Silenus]

Originally Posted by ajoosten

I also got a Lean Code on the drive after this noise started to happen.

There is an air leak. Smoke test the car, or pay someone to do it.

[kirill1221]

As far as i know, when the car is in neutral, it doesn't build as much boost as it does when you're in gear and theres a load. Listening to the video again, it could also be a belt driven accessory starting to fail. AC compressor, alternator, power steering pulley.

[ajoosten]

If you blip the throttle to almost redline the car generates a lot of boost for a split second. I was able to do this with a buddy and locate the leak fairly quickly. Turns out this was a loose boot connecting the turbos to the intercooler on the high pressure side. Car if fixed and pulls like it use to with no pig squeal.

[Jorgensen54]

Originally Posted by ajoosten

If you blip the throttle to almost redline the car generates a lot of boost for a split second. I was able to do this with a buddy and locate the leak fairly quickly. Turns out this was a loose boot connecting the turbos to the intercooler on the high pressure side. Car if fixed and pulls like it use to with no pig squeal.

Very glad to hear