[coolhandshin]

Acutally I got the new 650i couple of weeks ago,
and I apologize for posting here, since there aren't many 650i right now..

Here's my question:

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?

[JK479]

Originally Posted by coolhandshin

Acutally I got the new 650i couple of weeks ago,
and I apologize for posting here, since there aren't many 650i right now..

Here's my question:

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?

I noticed it as well when I did the Olympic Drive at a local dealer. I was driving a 650i convertible and as i was driving on a quiet road i could hear this "boom" which was quite loud. My GF and I thought it was another car's stereo but we realized it was coming from the car itself. This was an automatic. Really detracts from the sporty nature of the BMW to hear a thunk like that. DCT in the M3 is quieter than this. I have a feeling its normal and just the transmission shifting very quickly. Maybe its the sport transmission on the 650i. The 550i Sport Auto does not make this sound, i am sure of it.

Maybe its just a software fix, but i heard it too. And when i told one of the sales guys at the dealership, he scoffed it off as just a noise in my head, meaning i hadn't realy heard anything...

My guess, its the equivilant of the sound of downshift on a manual that is not rev matched...

[coolhandshin]

Originally Posted by jk3355

I noticed it as well when I did the Olympic Drive at a local dealer. I was driving a 650i convertible and as i was driving on a quiet road i could hear this "boom" which was quite loud. My GF and I thought it was another car's stereo but we realized it was coming from the car itself.

Thank you for your reply.

I am a little bit relieved that its just not my car (or maybe I shouldn't relieved..)

Did you hear that sound driving at high rpm?

[JK479]

Originally Posted by coolhandshin

Thank you for your reply.

I am a little bit relieved that its just not my car (or maybe I shouldn't relieved..)

Did you hear that sound driving at high rpm?

I did hear it all all shift points on the SPORT mode... i think what the boom is is just the transmission shifting very quickly which is what gives you the sound. its the gear i think...

I think the Lexus ISF has a similiar sound if i am not mistaken.

I guess its odd since the car itself is just so darn quiet...

[CJ]

I have this noise when shifting on manual mode at a high rpm into second and sometimes third. I kinda like the noise, its more subtle than the X5m which has a similar but even louder noise while shifting. The noise Im referring to seems to come from the exhaust of the car, almost like a bassy "cough" . The 650i exhaust seems to be alot more aggressive than the 5 series if I am correctly imagining your experience.
The transmission it very quiet but makes a soft turbine like sound under hard acceleration which it always had, now at 21500 miles.

[coolhandshin]

Originally Posted by CJ

I kinda like the noise, its more subtle than the X5m which has a similar but even louder noise while shifting. The noise Im referring to seems to come from the exhaust of the car, almost like a bassy "cough" .

Originally Posted by CJ

The transmission it very quiet but makes a soft turbine like sound under hard acceleration which it always had, now at 21500 miles.

Thanks for your reply. I think you are talking about the same sound I am referring to.

In fact I am ready to enjoy the sound if I'm told that it's an intended sound for SPORTS mode. Like you said it's almost like a bassy cough telling me that it's changing gears, and it's more evident on 2nd and 3rd gears then higher gears.

But I have never heard of such exhaust tuning and definitely have to find out if it's intended or not.

Actually I am a practicing physician and sometimes the patients just need to hear that they are o.k.

[CJ]

Same here! I definitely understand that.

[coolhandshin]

I took the car to the Services this afternoon,

The master technician took a ride with me and acknoweldged the booming sound.

He admitted he hadn't heard this kind of sound on any other cars, and while he thought that the sound didn't seem like there is something wrong with the gears or the exhaust, he couldn't say whether it was intended or not, either.

So he says he's gonna refer the case to BMW headquaters for an answer and it might take couple of months

I did get a general software update, but it wasn't particulary about the engine nor the transmission and it did not 'fix' the booming sound.