Intermittent choppy whistling under boost load

[DyeperRash]

So I have a bit of an issue. Based on what I have read around here on the forums and watching YouTube videos, I don't think it is turbo bearings, but I am not sure. I've replaced the DV to no avail. I am not sure where to do from here.

The best I can describe it, is its an intermittent choppy whistling noise. It does not happen every single time I accelerate hard (happens about 70% of the time), nor does it do it the entire power band of accelerating. It does not seem to matter if the engine is cold or warm. I have not noticed any extra smoke from the exhaust. I have linked a video that I took from inside the cabin and you can hear it. (It doesn't sound like any of the other videos I've seen that the turbos are 'whistling')

Below is the timeline/details of the issue and car.

2009 A4 Quattro - 64k Miles (Purchased about a month ago-- Totally stock, no noises)
I live at an altitude of 4,300 feet
Installed an APR Carbonio intake
Did not notice this odd intermittent choppy whistling noise after installing the intake
3-4 days after Intake install, got an APR Stage 1 tune done
Either that same day after leaving the shop, or the next day, I started to notice this odd noise while accelerating hard.
Can usually only hear the noise from about 2,000 - 3,800-ish rpm.
I do not hear the noise under normal/light driving-- Only when accelerating harder
Does not make the noise if sitting still and raising the revs
Sound immediately goes away after releasing the throttle
Installed a GFB DV+ Diverter Valve -- sound still there. No change. (Stock DV was the newer style, not the diaphragm style)
No codes from the VAGCOM
I took some logs of the requested boost/charge vs actual log from vagcom-- I am no pro at reading this, but it seems like I am not losing any boost. (At least the time that I was logging) VAGCOM RUN 1 VAGCOM RUN 2
However, sometimes I do think I am losing boost because I can see my needle slightly bounce as I am accelerating while the noise can be heard. However, this is not very often that I notice this.
The sound can still be heard if I change the APR program to 'stock', but it is not nearly as loud/often as running the 91 octane program.

I took it into the shop that did the APR tune to take a look. For $125, they did an initial diagnoses and checked a few different things, including removing the intercooler pipe and found some oil in it. Now they want to charge another $350 to take the downpipe off and take a look at the turbo to find out if there is any give/play in the shaft and to look at the bearings.

Is it possible that this is just the sound of air rushing in through the turbo or exhaust and its completely normal? The reason why I don't think its normal is that I can run the 'stock' program and I can still hear it, and this only reared its head after getting the stage 1 tune done.

Any thoughts anyone? Quite the head scratcher-- but I am no mechanic by any means.

The first part of the video is hitting it hard in automatic. Second part of video I am in 3rd gear hitting it hard, and then letting it rev down. You can hear it 2-3 seconds, 5 seconds, 10-11 sec, and 18-19 sec.

[van462]

I hear intake whistle, do you have the stock airbox to test with.

[1_clean_Audi]

i hear the whistle, maybe your turbo is going bad>? does it only happen when accelerating? or can you rev the car and hear it.?

[DyeperRash]

I hear intake whistle, do you have the stock airbox to test with.

I do-- I can give that a try. But whats interesting, is that this sound only appeared after getting the APR Stage 1 Tune. I already had the APR Intake before getting the tune and I never heard the noise.

i hear the whistle, maybe your turbo is going bad>? does it only happen when accelerating? or can you rev the car and hear it.?

Yes, it only happens when accelerating. (Mentioned in original post) Also, I cannot hear it while sitting in park and revving it.

[DyeperRash]

So I put back on the stock airbox and the issue is still there.

I need to do some more tests, but I think it actually only does it when the throttle is open between 50-75%. I don't think it does it when I put the pedal to the metal.

[van462]

One other thing you can check. On the very front of the turbo is the N75 valve that controls the wastegate. It has three hoses on it. One from the pressure side of the turbo that feeds the N75 from the bottom. A side or front hose that goes to the waste gate. The top port is the bleed port and feeds back at the air inlet of the turbo. Look these hoses over for cracks. You could also pull the hose off the N75 that goes to the wastegate actuator and pressurize it to 7 to 10 psi, verify the wastegate moves and see if it hold pressure of possible lose air thru the diaphragm.

[Rock803]

I'm having a similar issue. Some mods. New n75, new dv ( same with gfb dv+ or stock ). Tune, stock box with afe filter. Occurs between +/- 2500 to 3500 rpm. The sound is slower than the one in the video. Same throttle input (1/3rd) but goes away when pushed farther. Has a 'surge' feeling to it. Any help would be appreciated.
Thanks, Adam

The Edge

[Rock803]

Bump for someone's help.

The Edge

[AudiTony25]

I noticed this after the tune too.. Not sure the cause. So I had the tune before and after their most recent update, and it was after their update the car felt more powerful.. Also got more whistle


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[B8bully]

any updates on this i have the simliar problem ( whsilting and surging ) driving me insane

[rcprato]

Bad waste gate on turbo? You usually get the under boost code though with bad waste gate


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[Zuzuwu]

any updates on this i have the simliar problem ( whsilting and surging ) driving me insane

Compressor surge. Common with a lot of aftermarket tunes. There’s a reason the stock tune increases boost gradually instead of just pegging straight to 20psi


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[B8bully]

Pulling turbo this weekend checking waste gate and putting new seals thanks guy appreciate it I'll post if I fix ussue

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[Forzdaze96]

Pulling turbo this weekend checking waste gate and putting new seals thanks guy appreciate it I'll post if I fix ussue

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I'm guessing you didn't fix this?

I had a new engine installed, and they didn't swap over my turbo with only 20k on it. I heard this exact sound for a bit, and just installed a JB4 2 weeks ago, using stage 1 map it is VERY noticeable now. I would like to solve as well now, as everything i've read and seen points to turbo itself.....