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      08-27-2011, 03:21 PM   #1
coolhandshin
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Booming sound when shifting up in SPORT mode?

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I found out that NORMAL and SPORT mode definitely have different exhaust sound when accelerating.

But annoying thing is, when in SPORT mode and accelerating hard, there is this 'booming' or 'humming' sound (that fills up the ears like low bass sound) for ~0.5 seconds while the gear automatically shifts up.

NORMAL and COMFORT mode does not produce this booming sound even at high rpm shifting.
Also, if you are in SPORT mode and not in high rpm, it also does not produce such sounds.

Do you also have similar experience or is my car a little weird?
Am I suppose to enjoy this sound since it's a V8?
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      08-27-2011, 08:43 PM   #2
jettie1767
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You must be flooring the car a lot. I haven't heard the booming sound you're talking about.
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      08-27-2011, 10:28 PM   #3
coolhandshin
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Quote:
Originally Posted by jettie1767 View Post
You must be flooring the car a lot. I haven't heard the booming sound you're talking about.
Still in breaking in period, so I'm not flooring it really.
In fact I'm not going past 4500 rpm but I get the booming when I reach around 3000 with gear shifting up.

Since its only audiable during the short moment when shifting up, my guess and others is that its got to do with the new transmission
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      08-29-2011, 07:01 AM   #4
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I haven't heard that at all unless it's barely audible. Maybe you can post a recording of the sound.
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      08-29-2011, 06:40 PM   #5
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I have driven the new convertible less than 250 miles, so I do not suggest that I know what is going on, but I do know that these sophisticated new transmissions are controlled by chips that do a rev-match blip of the throttle on some shifts...any chance that's what you're hearing...?
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      08-30-2011, 12:14 PM   #6
coolhandshin
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Ok so here's an update:

I took the car to the BMW services and they agree there is definite booming sound when automatically upshifting in SPORTS mode, however they aren't quite sure why it's causing it, but they don't think it's something wrong cause it's doesn't sound like something's breaking or out of place, instead one could possibly enjoy the sound. well, maybe.. they will report the case to BMW headquaters.

I enquired my odd sound to a very experienced mechanic who has been dealing with BMW and other german cars for a long time, and well reputated in a internet BMW community in Korea, and at once he says it's got to be something to do with that dual flap on the exhaust.

It is known that the exhaust flap opens only at certain rpm's and when you accerelerate and rpm goes up, the flap opens. At this time, there is no booming sound. However when you constantly accerelerate, the car shifts into higher gear, and the rpm suddenly drops. The flap that was opened closese, and it creates a stoppage of air or whatever aerodynamics involved, and that's when you hear the booming sound.

It's not suppose to be any harm to the car.

However I wonder if this happens to all the 650i Converts and Coups with dual speed variable flaps or just to some? and would this sound be intended?

I did try to get it on video, but with my iPhone 4, the bass sound was not recorded well and could just barely hear it. In real life, it is quite noticeble.
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      08-30-2011, 10:07 PM   #7
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Mine does this in sport mode too but I'm certain this is how it's supposed to work. It makes the car sound a bit more angry.
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      08-30-2011, 11:51 PM   #8
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Quote:
Originally Posted by xraymd View Post
Mine does this in sport mode too but I'm certain this is how it's supposed to work. It makes the car sound a bit more angry.
As someone mentioned before, it is a bit odd comparing to the rest of engine and exhuast sounds which aren't the most aggresive i've heard.

It does make the car more sportier and fun, letting me know its changing gears at a fast pace but I really got to find out if it's really intended to really stary enjoying it
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      09-01-2011, 10:50 PM   #9
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Sad your service guys don't know about this.

A throttle blip with gear changes is fairly common on many newer performance cars, not just the 6. The altered sound isn't covered in the manual but neither is the fact that switching to sport mode makes the transmission use fewer gears or that it holds gears longer. Don't worry about it, your car is OK
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      09-12-2011, 03:21 PM   #10
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Something BMW has been doing to all turbo engine exhausts is a raw popping/bubbling/gurgling at liftoff or when shifting. It happens on my X3 35i, my 535i loaners, the 335i, the new Z4 28i, and the x5 50i. Do not worry. When driving past people, it is a very impressive noise.
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      09-12-2011, 06:19 PM   #11
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Quote:
Originally Posted by juddholland View Post
Something BMW has been doing to all turbo engine exhausts is a raw popping/bubbling/gurgling at liftoff or when shifting. It happens on my X3 35i, my 535i loaners, the 335i, the new Z4 28i, and the x5 50i. Do not worry. When driving past people, it is a very impressive noise.
Thats not the same sound they are talking about. Only downshifts in Sport and Sport plus. Sounds like a boom and actually distracts you will you are moving along. almost like there is a kid playing a boom box next to your head... infact when i drove the 650i, i thought it was a loud car next to me playing the stereo loud.

I hope BMW comes up with a fix to it. I bet the software will be updated... and problem solved...
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      09-12-2011, 06:24 PM   #12
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Definitely a different sound. I came out of an e93 335, and it didn't make this sound.

jk3355 - You're right in the description of the sound, just like a boom box in the next lane. But why are we waiting for a fix? It's a great sound, and it's not by accident. If you don't like it, keep the tranny out of sport mode and you won't have to hear it. You can set sport mode so that the chassis goes firm but the transmission stays in standard mode.
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      09-13-2011, 08:30 AM   #13
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Quote:
Originally Posted by xraymd View Post
Definitely a different sound. I came out of an e93 335, and it didn't make this sound.

jk3355 - You're right in the description of the sound, just like a boom box in the next lane. But why are we waiting for a fix? It's a great sound, and it's not by accident. If you don't like it, keep the tranny out of sport mode and you won't have to hear it. You can set sport mode so that the chassis goes firm but the transmission stays in standard mode.
No I'm almost positive it's the same sound. The way you describe it illuminates an aspect of the way it sounds to me. I only heard it once in a 335, but all others many times. I'll post a video of my X3 making the noise soon.

Listen to the occasional booming/popping in this video. It's very apparent. If it's not the same, then I don't know. http://e89.zpost.com/forums/showthread.php?t=575302
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      09-13-2011, 11:31 AM   #14
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xraymd, jk3355 - definitely the same sound I'm talking about; boombox in my ear when shifting.

I tried the video juddholland mentioned on the new 4 cylinder Z4; I don't think it's the same sound.
And also it's kinda hard to hear a bubbling sound on a 650i, contrary to what some others have mentioned..
Maybe I haven't revved high enough, just getting over 5000rpm as I gradually go over the break-in limits.


I came across the exact same sound that I was talking about. The video's not on a 650i, rather it's on a X6M with a 6 geared M steptronic, and I dunno if it's coming from the same mechanism or not.

But it's definitely the same sound at the perfect timing as I hear it, check it out:





Also on a 650i, I managed to catch a glimpse of that sound.
Play from 1:00 to 1:08.





So I hear the same sound on an M, I am happy..?

Last edited by coolhandshin; 09-13-2011 at 12:44 PM..
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      09-14-2011, 12:42 PM   #15
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Don't know about the X6M video, but your video captures is perfectly.
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      09-16-2011, 01:28 PM   #16
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I got to drive a new 650i convertible about a month ago and noticed the "bass hit" sound when shifting in sport mode only. Seems like it was only under moderate to hard acceleration. I figured it had to do with the flapper valve or possibly from turbo blow-off dumping into the exhaust tract during the shift. It was definitely distracting. My salesman didn't have much experience with the car as it was the first new 6er they'd received. He was a little startled by it too since he'd never noticed it either. Definitely strange and not something I'd like to hear all the time.
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