Request Help Diagnosing Extra "Air Sound" with Burbles & Pops

[jmciver]

So yesterday I noticed a new sound coming from under/behind the car in addition to the normal burble and pops/overrun. It sounds like a quick, split second burst of air, almost like a very quick blow-off, at the beginning of the overrun and then right at the completion of the overrun sequence. It almost sounds like a slight, pressurized exhaust leak. So the sequence is: lift off gas -> "air sound" -> burble and pops/overrun -> "air sound"

It only makes this sound when the car is in Sport or Sport+, when overrun is active. In Efficient mode, when overrrun is not active, there is no air sound so I don't think it is some component that is flopping around under the car. My car was at the dealer last week getting some work done: oil pan replacement and trans oil drain/refill. My first thought is that maybe a vacuum fitting may be loose or something, which might explain the very brief air noise I am hearing, or possibly an exhaust leak that only occurs with the overrun. But other than that, I don't have s clue as I am not familiar with what may have been taken apart when the other work was being done.

I am pretty sure I am not "hearing things" even though I just got my car back from the dealer. It can be easy to get a bit paranoid and your mind plays tricks on you. But I have always been a fan of the burbles and pops, sometimes listening to it with the windows down and radio off (I know, a bit weird - but I am sure I am not alone ). So when I first heard this extra air sound, I knew something didn't sound right. I don't have any CELs or warning lights and the car otherwise seems to be running fine.

So anybody with a '16+ stock ZCP care to listen to their own overrun to help verify my mind is not playing tricks on me? Any ideas what this could be? I plan to take it back to the dealer but would like to be armed with some troubleshooting ideas if possible. While I can hear the air noise in question while driving with the windows down and radio off (especially if close to barriers on the side of a road or in a tunnel), I can also hear it very clearly when blipping the throttle in the garage - as the noise bouncing off the walls makes it real easy to hear. The engine just needs to be a bit warm since the burble and pops don't become active until ~2-3 min after the engine is started, especially if it is a cold start.

Thanks!

[apexit]

My intakes exaggerate turbo noises. Lately I've been running around in Sport+ mode and have noticed this too. It's the blow off/ diverter valve, I guess the extra boost or other settings makes it more pronounced.

[jmciver]

Originally Posted by apexit

My intakes exaggerate turbo noises. Lately I've been running around in Sport+ mode and have noticed this too. It's the blow off/ diverter valve, I guess the extra boost or other settings makes it more pronounced.

That could make sense, but this sound is very specific and occurs a split second before the burble and pops, and then right after the burble and pops stop - and sounds out of place. This is regardless of RPM. I know about the intake/turbo spool noise you are talking about. I hear it every time I am in Sport+ and hit the gas hard.

However, I never remember hearing any type of blow-off valve noises from this car as my understanding is that the blow-off is recirculated back into the intake and not to atmosphere (I could be wrong here though ). As I mentioned above, I can make it do this sound even blipping the throttle at idle - where boost buildup should be very low. But of course the most convincing thing to me is that I am VERY confident it was not there before.

I just wish I had a local, stock ZCP owner close to me to listen to since I know exactly what to listen for to verify with certainty that something is amiss (or not).

[apexit]

You hear it after the burbles too? If you're hearing it 2x when you let off the throttle it's def. not one of the fun turbo noises.

[jmciver]

Originally Posted by apexit

You hear it after the burbles too? If you're hearing it 2x when you let off the throttle it's def. not one of the fun turbo noises.

Yup, it is almost like it is a switch noise, turning the burbles on, then off. Except the switch noise sounds like a very quick puff of air, like when you disconnect an air hose from filling your tires with air.....

[CaryTheLabelGuy]

It's the EWGs opening. It's actually a rattle.

The EWGs have more function than just controlling boost. They play a large roll in Sound Tuning as well. In aggressive burble overrun mode, the DME opens the EWGs.

[jmciver]

Originally Posted by CaryTheLabelGuy

It's the EWGs opening. It's actually a rattle.

The EWGs have more function than just controlling boost. They play a large roll in Sound Tuning as well. In aggressive burble overrun mode, the DME opens the EWGs.

Thanks for chiming in..... So why is it that I don't remember hearing them before? I would like to think my mind is not playing tricks on me. I was thinking that something may not have been put back together properly during the oil pan replacement work that was just done (i.e. some interference removal since the sub frame needs to be dropped to get to the oil pan).

What would be the next step to possibly address the issue?

[CaryTheLabelGuy]

Originally Posted by jmciver

Thanks for chiming in..... So why is it that I don't remember hearing them before? I would like to think my mind is not playing tricks on me. I was thinking that something may not have been put back together properly during the oil pan replacement work that was just done (i.e. some interference removal since the sub frame needs to be dropped to get to the oil pan).

What would be the next step to possibly address the issue?

You're very welcome.

Wastegate rattle gets worse with time. IMHO, they are always audible to me. Every S55 I've heard had it, some are just worse than others.

If it's supper annoying, BMW would need to replace the turbos to stop it and it would probably eventually come back.

[jmciver]

Originally Posted by CaryTheLabelGuy

You're very welcome.

Wastegate rattle gets worse with time. IMHO, they are always audible to me. Every S55 I've heard had it, some are just worse than others.

If it's supper annoying, BMW would need to replace the turbos to stop it and it would probably eventually come back.

Well that doesn't sound too encouraging, especially since the sound seemed to coincide with some recent repair work. I was hoping this would be a "relatively" easy fix due to something that may not have been put back together properly, like a loose hose clamp or something as the noise I am referring to sounds like a split second release of air to the atmosphere, not a rattle. Based on the info you have provided, it sounds like the valve that controls air from the EWG (or some type of air control device) for the overrun feature is not operating properly, which is why I can now hear the quick, but noticeable, puff of air right before and right after the overrun sequence, when I didn't hear it before.

So if I do take this back to a dealer to investigate this air noise, what would be your recommended tactic? Is there any more knowledge I can use as ammo to help address this issue? I always like to come in armed with specific info so that the dealer knows they are not dealing with an amateur when it comes to troubleshooting problems, and to help prevent a complete "Easter egg" hunt as they try to diagnose the problem. What always sets me off with any dealer is when they give me the automatic response of "that is normal" or something similar without really considering that something may be wrong that requires at least some basic troubleshooting to help diagnose the issue. This is even after I provide them a detailed description of the problem.

[CaryTheLabelGuy]

Originally Posted by jmciver

Well that doesn't sound too encouraging, especially since the sound seemed to coincide with some recent repair work. I was hoping this would be a "relatively" easy fix due to something that may not have been put back together properly, like a loose hose clamp or something as the noise I am referring to sounds like a split second release of air to the atmosphere, not a rattle. Based on the info you have provided, it sounds like the valve that controls air from the EWG (or some type of air control device) for the overrun feature is not operating properly, which is why I can now hear the quick, but noticeable, puff of air right before and right after the overrun sequence, when I didn't hear it before.

So if I do take this back to a dealer to investigate this air noise, what would be your recommended tactic? Is there any more knowledge I can use as ammo to help address this issue? I always like to come in armed with specific info so that the dealer knows they are not dealing with an amateur when it comes to troubleshooting problems, and to help prevent a complete "Easter egg" hunt as they try to diagnose the problem. What always sets me off with any dealer is when they give me the automatic response of "that is normal" or something similar without really considering that something may be wrong that requires at least some basic troubleshooting to help diagnose the issue. This is even after I provide them a detailed description of the problem.

I assure you, it's not a puff of air. The EWG commands the wastegate full open right as the burble sequence starts and slams them closed when the burble sequence is finished.

The electric stepper motors that make up the EWG units can have a weird sound when they move and the wastegate actuator arms do have a rattle (what I was speaking of earlier).

What was your recent repair? Did it involve downpipes and/or turbos?

[jmciver]

Originally Posted by CaryTheLabelGuy

I assure you, it's not a puff of air. The EWG commands the wastegate full open right as the burble sequence starts and slams them closed when the burble sequence is finished.

The electric stepper motors that make up the EWG units can have a weird sound when they move and the wastegate actuator arms do have a rattle (what I was speaking of earlier).

What was your recent repair? Did it involve downpipes and/or turbos?

It was an oil pan replacement. While not directly related, I was thinking that when taking the car apart for the oil pan job, which required dropping the sub frame and other interference parts to be removed, something else was either "bumped" or not put back together properly, hence the new sound I am hearing with the overrun sequence.

[CaryTheLabelGuy]

Originally Posted by jmciver

It was an oil pan replacement. While not directly related, I was thinking that when taking the car apart for the oil pan job, which required dropping the sub frame and other interference parts to be removed, something else was either "bumped" or not put back together properly, hence the new sound I am hearing with the overrun sequence.

Can you try and get a video of it?

[jmciver]

Originally Posted by CaryTheLabelGuy

Can you try and get a video of it?

I will give it a shot, although I suspect trying to capture on audio what I am hearing may be challenging.

[CaryTheLabelGuy]

Originally Posted by jmciver

I will give it a shot, although I suspect trying to capture on audio what I am hearing may be challenging.

Probably, but it would be better than nothing.

[jmciver]

Ok, I took two videos a little over 20 seconds each, blipping the throttle several times. The first video is from the top of the car, on the passenger side of the engine compartment. The second video is from the bottom (side) of the car, also on the passenger side. The offending noise in question can be heard in each video, although it is easier to hear in the second video. It is also harder to hear the noise at the beginning of the overrun sequence, but you can definitely hear it at the end of each overrun sequence. Once you know what to listen for, it will be easier to hear it at the beginning of each overrun sequence.

https://youtu.be/nxD_OTGb_64

https://youtu.be/_bQ9Q6Pr1XA

[CaryTheLabelGuy]

Originally Posted by jmciver

Ok, I took two videos a little over 20 seconds each, blipping the throttle several times. The first video is from the top of the car, on the passenger side of the engine compartment. The second video is from the bottom (side) of the car, also on the passenger side. The offending noise in question can be heard in each video, although it is easier to hear in the second video. It is also harder to hear the noise at the beginning of the overrun sequence, but you can definitely hear it at the end of each overrun sequence. Once you know what to listen for, it will be easier to hear it at the beginning of each overrun sequence.

https://youtu.be/nxD_OTGb_64

https://youtu.be/_bQ9Q6Pr1XA

Those are the EWGs actuating. Just like I thought.

I wouldn't worry about it, it's very normal as even my ZCP does this and did this since brand new.

[jmciver]

Originally Posted by CaryTheLabelGuy

Those are the EWGs actuating. Just like I thought.

I wouldn't worry about it, it's very normal as even my ZCP does this and did this since brand new.

I guess what is most frustrating is the fact that I don't remember hearing this noise before the recent work was done. The videos were able to capture it better than I thought they would, when relatively close to the source. However, I can hear the EWG noise sitting in the drivers seat (with the windows down) and it is almost as discernible as it is in the video. I still may take my car to the dealer to see what happens. If they have a ZCP on the lot, maybe I could do a direct comparison to put my mind at ease (or possibly get a warranty repair done)...... That said, I am not a fan of taking things apart that don't really need to be taken apart either.

At least I have some knowledge of what I am dealing with now - thanks.