[mannsourr]

Hello everyone,

I recently installed the MPPSK to my 540i, however, I immediately noticed that there is a rather loud and annoying whistling noise that appears with hard acceleration; you can hear it very well in the video below, especially 50 seconds into the video during my second acceleration run. My theory is that this is due to the exhaust not fitted correctly (i.e. could be a loose clamp?) and a small leak is causing the whistling noise under high pressure from hard acceleration.

The dealer has been very cooperative in trying to trouble shoot this issue and has so far two created PuMA cases with BMW, however its still not resolved. They were also very open to me attending the troubleshooting sessions with them (at my request) and to test the car after each attempt at fixing it.

Unfortunately, I had to take my car back from them before they could complete the job due to the ongoing COVID-19 situation causing them to close the service center temporarily due to local regulations.

I am curious to hear if any of you faced any similar case or can propose any ideas of how to approach/troubleshoot this problem? Perhaps we are too focused on the exhaust and the issue is coming from the engine bay?

[kring]

Could be the bumper or something closer the the muffler, because the MPPSK is different all the way from the downpipe, that could be a sharp edge or the air getting pinched that's causing that. line the bumper edge on inside with painters blue tape, look for any edges along the muffler, mount points, pipes. could be as simple as a drop of weld on the edge of the muffler. also on the exhaust tips, have you tried removing those to see if it's just them? It could be air getting sucked in through the tip where the pipe is facing the front of the car. those tips are sharp so be careful, and most whistling is caused by a sharp edge or a hole or indent that causes a pressure imbalance and then vibration.

That would be the easiest check, my first thought was it is exterior related since I only heard it as the car built up speed, when you reved and started out it's blowing air through exhaust and I didn't hear it. or do you hear it then too?

[mannsourr]

Thanks kring! I will certainly try those ideas and let you know if it helps.

Btw, I found a couple videos on YouTube with similar issues, very strange for this issue to be this common. I'm beginning to think its a manufacturing defect?

(@1:19)

(@2:01

[kring]

Your's is way more pronounced than the those two videos. I would suspect they don't hear it while driving. The first video when I hear it most, It keeps whistling while he's coasting at high speed, just not as loud, so that tells me it's probably on the exterior. I'm going to put my money on it being the tips as most likely cause or the bumper inside edge right near the the tips. localized to that square foot of the car. I'm also thinking it's not inside the exhaust or you would hear it at slow speeds.

good luck, keep us posted.

edit - listing a few more times, it sounds like a sucking whistle vs a blowing whistle... not sure why I think that... but it reminds me of a jet engine or intake point. and the only place it's sucking in air could be at the tips. it sounds too high pitch to be coming all the way from the engine through the exhaust, I would think anything that high pitch up by the turbos would be totally drowned out by the time it made it through the full exhaust.

[nsa100]

Mine whistled when I first had it installed on heavy acceleration at high rpm.

The whistling stopped after about 6 months. Could just harmonics until the exhaust 'beds in'. The overall tone of the exhaust becomes slightly deeper as well.

[Bibbles]

I've never noticed anything on mine, is it something you could hear from inside the car or just what you noticed when you had the go pro on the back? Any excuse for me to get out in the car and accelerate hard is always welcome!

[nsa100]

On mine it was just when the windows were down.....so I could appreciate the sound