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View Full Version : Anyone else with booming sound when shifting up in SPORT mode?


coolhandshin
10-10-2011, 05:03 AM
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 on the exact moment the gear automatically shifts up.

It's almost like a boombox next to my car during shifting.

I have posted this on bimmerpost forum, and some have agreed they hear that same sound; some enjoy it, while some find it distracting.

BMW Services don't know if it's intended or abnormal; they say they'll get back to me.

Anybody else also with the same strange noise?

Do you like it?

Here's a sample; play from 1:00 to 1:08.
The booming sound is somewhat more louder and boomy than the video

http://vimeo.com/25390582

dkreidel
10-10-2011, 03:34 PM
Yep - that is a "feature" on the AT cars - and one of the reasons I purchased a MT 650; mine doesn't do it but all the AT cars I test drove did.

Read some of the car rags road tests - they talk about it quite a bit.

dk

coolhandshin
10-10-2011, 04:46 PM
Read some of the car rags road tests - they talk about it quite a bit.

dk

Actually I read those road tests quite closely for any mention of the booming sound but couldn't find any.

Can you give a link to what you read?

Thanks

RocX6
10-12-2011, 03:37 PM
I have a vert and I hear it all the time (always in Sport). The first time I heard it I thought it was cool. I never thought that it wan't normal, just figured it involved the Turbo. But now I'm contacting the performance guy at my dealer to get some insight into it. This post made me more curious. I'll post any info I get. :thumbup:

long time
10-16-2011, 12:07 PM
I'm a boomer too

So is my F13...

car-fan
10-17-2011, 08:17 AM
I have a vert and I hear it all the time (always in Sport). The first time I heard it I thought it was cool. I never thought that it wan't normal, just figured it involved the Turbo. But now I'm contacting the performance guy at my dealer to get some insight into it. This post made me more curious. I'll post any info I get. :thumbup:

Personally, I can't get enough of it. Compared to the other cars with the N63 TTV8 I believe the 6 may be the most vocal. The other cars are library quiet in comparison "on or off" throttle. I'm pretty sure it has to do with the exhaust tuning via the ECU. I envision it to be similar to one of the effects created by pressing the Sport button on the current Cooper S models which creates "backfire style pops" when you let off the throttle.

Just my two cents :thumbup:

tbod
01-01-2012, 09:20 AM
I know this is old but I'm bored.......

Turbo bypass valves relieving pressure to the exhaust system. If you hear some people on some imports (supras, etc) run the bypass to atmosphere and they have that loud whooshing sound when letting off the throttle. Our cars just send it out the exhaust. It sounds weird because our turbos are so small. The turbo vanes still spin when off the throttle so the pressure has to be routed somewhere then the throttle valves are closed.

My theory anyways.


Bypassed to atmosphere....

http://www.youtube.com/watch?v=0ttbegQ0kT0

Socal1979
01-10-2012, 02:22 PM
I noticed the same sound when shifting gears in my 2012 650ic (automatic). The sound feels like it's coming from the back or vibration of the trunk lid. I took it in to the dealer and told them of the noise. They told me everything was normal on the car.

Frankly, it's kind of annoying. But I can live with it.

I love the car.

Elias
01-10-2012, 02:54 PM
I'm a stickler for any abnormal noise, I had the ticking sound on my 535 and it drove me crazy. I don't recall any booming sound at all but I will be looking for it next time I drive my car.:dunno:

Itinj6
01-11-2012, 06:30 AM
I personally love that booming sound. It's more prominent in sport mode from 1st- 2nd gear and gets more faint when shifting into higher gears.

I'm really curious as to how it sounds outside the car though

Elias
01-11-2012, 07:15 AM
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 on the exact moment the gear automatically shifts up.

It's almost like a boombox next to my car during shifting.

I have posted this on bimmerpost forum, and some have agreed they hear that same sound; some enjoy it, while some find it distracting.

BMW Services don't know if it's intended or abnormal; they say they'll get back to me.

Anybody else also with the same strange noise?

Do you like it?

Here's a sample; play from 1:00 to 1:08.
The booming sound is somewhat more louder and boomy than the video

http://vimeo.com/25390582

Sorry but I didn't hear any abnormal sounding Boom in the video, just sounded like a powerful V8 roar taking off!:confused:

TopDownInFL
01-11-2012, 11:04 AM
I know the sound you're talking about - I assume that's one of the turbos kicking in for the lower band.

Itinj6
01-11-2012, 07:30 PM
My guess is that it's the blowoff valve.

john mclane
06-08-2012, 02:17 PM
Confirmed from BMW headquarters: It's the closing of the muffler valve causing air backpressure in the muffler and then the "booming" noise. Interesting that they "fixed" in the first attempt by replacing some ARS valves. The sound remained the same and when I threatened a lemon process, they contacted HQ that stated the sound is like that. Allegedly they reproduced the sound on a new model there, will pick it up later and "ll want to hear that happening.
Still annoying nonetheless, Perhaps I'll push for a M muffler replacement...

Itinj6
06-08-2012, 02:32 PM
I personally love that sound. It was much more prominent in my non M-Sport, probably because the exhaust note on it was quieter.

john mclane
06-08-2012, 03:17 PM
Just got the car back
I tested a 650 with m package and the noise and booming nuisance are the same, so swapping won't do.

tbod
06-08-2012, 03:29 PM
Haven't been on here in awhile. The booming sound is the second clutch in the 'dual-clutch' assembly engaging. It has to do it quick so the first clutch doesn't drag and the acceleration loss is minimal. In non-sport mode or light acceleration, the computer engages it slower so it's not as harsh. The sound is well worth it for shifting speed. I got to drive a Lamborghini Aventador a few weeks ago and it has a single clutch design. It's an awesome car but the shifting was slow as hell. Made me appreciate the dual clutch in my car.

john mclane
06-08-2012, 03:53 PM
Haven't been on here in awhile. The booming sound is the second clutch in the 'dual-clutch' assembly engaging. It has to do it quick so the first clutch doesn't drag and the acceleration loss is minimal. In non-sport mode or light acceleration, the computer engages it slower so it's not as harsh. The sound is well worth it for shifting speed. I got to drive a Lamborghini Aventador a few weeks ago and it has a single clutch design. It's an awesome car but the shifting was slow as hell. Made me appreciate the dual clutch in my car.

650i is an automatic, not dual clutch...


Booming noise is from the counter pressure within the muffler as the valve closes

tbod
06-08-2012, 04:54 PM
650i is an automatic, not dual clutch...


Booming noise is from the counter pressure within the muffler as the valve closes


Yes the automatics are dual-clutch. Google dual clutch transmissions.


So you're saying the exhaust valves are closed under full acceleration and open when shifting? I don't understand the purpose of that.

john mclane
06-08-2012, 05:07 PM
Yes the automatics are dual-clutch. Google dual clutch transmissions.


So you're saying the exhaust valves are closed under full acceleration and open when shifting? I don't understand the purpose of that.

They open under acceleration on sport mode, during shifting they close as the rpm drops, which causes the back pressure and the nasty boom noise

I forced them open and tried again, the noise is mostly gone...

Itinj6
06-08-2012, 06:11 PM
My valves are open all the time, no matter what mode I'm in.

john mclane
06-08-2012, 09:12 PM
My valves are open all the time, no matter what mode I'm in.

What did you do? Is the sound less puny?

Itinj6
06-08-2012, 09:17 PM
What did you do? Is the sound less puny?

I did nothing other than take delivery lol.

When I cold start it, only the outer pipes are open. When the car warms up and idles come down, the inner valves open and stay open. I flipped through the various modes and no change. Funny as I think it sounds better (throatier / louder) with the valves closed.

Bönz
06-09-2012, 04:04 AM
I've never noticed a booming. I'll run this experiment today. I don't hear it in the vid.



Yes the automatics are dual-clutch. Google dual clutch transmissions

Nope. The 8 speed auto in the 6er is a ZF torque converter / planetary gear based slush box. One of the best in the world IMO, but a slush box nonetheless.

The only clutches in it are the band clutches surrounding the ring gears on each planetary set and the torque converter's lock-up clutch. These are not the clutches BMW refers to in a DCT.

DCTs (as found on the M3, M5 and M6) are fundamentally manual based synchromesh transmissions with electro-hydraulic control and two wet concentric input clutches. One tied to the even gears, one tied to the odd.

john mclane
06-09-2012, 04:27 AM
i've never noticed a booming. I'll run this experiment today. I don't hear it in the vid.





Nope. The 8 speed auto in the 6er is a zf torque converter / planetary gear based slush box. One of the best in the world imo, but a slush box nonetheless.

The only clutches in it are the band clutches surrounding the ring gears on each planetary set and the torque converter's lock-up clutch. These are not the clutches bmw refers to in a dct.

Dcts (as found on the m3, m5 and m6) are fundamentally manual based synchromesh transmissions with electro-hydraulic control and two wet concentric input clutches. One tied to the even gears, one tied to the odd.

+1

tbod
06-09-2012, 07:15 AM
The ***8216;heart***8217; of the new double-clutch transmission in technical terms is formed by the two oil-cooled wet clutches. One of the two clutches is for the even (2, 4, 6, 8), the other for the uneven (1, 3, 5, 7) gears and, in addition, for the reverse gear.

While driving, one of the two clutches is always closed, the other is open. When accelerating ***8211; and when shifting down ***8211; the clutches are activated in an alternating process, one after the other. When shifting gears, therefore, the first clutch opens just as the second clutch is closing.



Yes all automatics have a TC but the clutches refer to the activation on the gear sets on a particular shaft (there are 2).


I never said that there was a clutch disc on a pressure plate which it sounds like you were referring to. I've built several transmission in my life so I understand how they work. The BMWs is a work of art. Only quicker shifting car than my 650 I ever drove was a new 458 Italia.

southern6er22
06-09-2012, 07:56 AM
Nope. The 8 speed auto in the 6er is a ZF torque converter / planetary gear based slush box. One of the best in the world IMO, but a slush box nonetheless.

The only clutches in it are the band clutches surrounding the ring gears on each planetary set and the torque converter's lock-up clutch. These are not the clutches BMW refers to in a DCT.

DCTs (as found on the M3, M5 and M6) are fundamentally manual based synchromesh transmissions with electro-hydraulic control and two wet concentric input clutches. One tied to the even gears, one tied to the odd.

Wow. This post is going to require a lot of Googling/Wikipedia-ing to figure out what you just said lol. All sounds good to me though :)

Bönz
06-09-2012, 08:36 AM
The 'heart' of the new double-clutch transmission in technical terms is formed by the two oil-cooled wet clutches. One of the two clutches is for the even (2, 4, 6, 8), the other for the uneven (1, 3, 5, 7) gears and, in addition, for the reverse gear.

While driving, one of the two clutches is always closed, the other is open. When accelerating – and when shifting down – the clutches are activated in an alternating process, one after the other. When shifting gears, therefore, the first clutch opens just as the second clutch is closing.



Yes all automatics have a TC but the clutches refer to the activation on the gear sets on a particular shaft (there are 2).


I never said that there was a clutch disc on a pressure plate which it sounds like you were referring to. I've built several transmission in my life so I understand how they work. The BMWs is a work of art. Only quicker shifting car than my 650 I ever drove was a new 458 Italia.

With all due respect, and please excuse my subtlety, but you are just plain wrong. :)You are describing the DCT "Dual Clutch Transmission", which I mentioned in my post. It does use two wet clutches to transmit engine torque from the flywheel to the twin odd/even trans input shafts as you explained. These are great transmission and I hade one in my E92 M3.

BUT, and this is a big BUT, the regular (non-M) 6ers DO NOT use the DCT. They are equipped with the ZF 8HP torque converter based automatic transmission. It has one input shaft, not two. Transmissions do not require TCs and clutches to drive the inputs. It's one or the other.

Also, BMW does not currently market an 8 speed DCT.

I too have rebuilt trannys. I rebuilt my first engine when I was 14, I have two degrees in engineering and have worked on cars as an automotive engineer and enthusiast for 26 and 40 years respectively. I also know what I am talking about. I suggest you do more homework.