Think I detected a new sound from my exhaust on high RPM shifts?

[BMW135pls]

Lately I think I detect a new sound that I haven't heard before. This sound is only detectable during high RPM full throttle shifts. Actually the sound is reminiscent of something an F1 racer would make, it's really not a bad sound at all lol. According to my memory, it's a new sound so it may not be indicative of a good thing. No engine codes have been thrown aside from the inevitable kitty code.

The sound change may be due to more recent mods like the charge pipe, cold air intake, or OCC. I may get unlazy and try to take a recording of the sound if it's needed, but my hope is that it is a common phenomenon. The sound is sort of like, for a split second everything in the exhaust track opens wide up and the growl engine tone goes away, and you are left with just the upper rasp sound, which is louder than it normally is for a split second until the next gear gets clutched in and the sound returns to normal.

Does anyone know what I'm the hell I'm on about, or should I take a video of it?

[BMW135pls]

Sorry I haven't been able to record a clip of the sound due to how infrequent it is, but I just experienced it the other day. It is definitely not RPM limiter because even when I shift at 6k the sound can be heard when it feels like showing itself. Actually it can be a not very good sound when it shows up, sounds sort of cheap to me, like the sound a peasant Honda makes when it's got a fully open exhaust being powered by a weak farty engine. Kind of a high frequency raspy fart when shifting. It (the negative sound) is only really noticeable when using lots of throttle and while shifting, so I am thinking it could be an artifact of the VANOS VVT system, or possibly trans slip.

I will try to get a recording when it is acting up, I know that will be very helpful. It sounds like an extra sound that shouldn't be there, it's not burble. Instead of BRRRRRRRRM BRRRRRRRRM it'll sound like BRRRRRRRRV V v v BRRRRRV V v v.

[jisham]

Is it over-run popping like people get with the PPK/PPK2?

I'm new here, so I can't explain it, but if you search for PPK and overrun, you can probably find some videos demonstrating the noise to see if its similar to what you're hearing.

-john
2011 135i
(prev 2000 323i)

[BMW135pls]

Originally Posted by jisham

Is it over-run popping like people get with the PPK/PPK2?

I'm new here, so I can't explain it, but if you search for PPK and overrun, you can probably find some videos demonstrating the noise to see if its similar to what you're hearing.

-john
2011 135i
(prev 2000 323i)

I searched PPK overrun and found that it seems like it is referring to lift throttle burble. That's not it, the sound I am referring to is not keyed by changes in throttle, only during shifts with throttle constant.

[Andrewcoja]

You saying it sounds like an F1 car makes me think it's just the sound of the revs being dragged down my the next gear. It happens with the DCT if I hit the throttle and shift around 4k. That's in non sport mode. In sport mode it makes a kind of fart sound because it shifts faster.

[Esteban]

Originally Posted by Andrewcoja

You saying it sounds like an F1 car makes me think it's just the sound of the revs being dragged down my the next gear. It happens with the DCT if I hit the throttle and shift around 4k. That's in non sport mode. In sport mode it makes a kind of fart sound because it shifts faster.

You should try (if you haven't already) driving with the DTC button pressed once. This turns on the DTC mode (Dynamic Traction Control) and makes those little explosion sounds you're talking about while shifting the DCT even louder and it also makes the computer nannies less intrusive so you can have some fun (a little slippage) while you're driving. This, and in the manual mode with the sport button pressed is the way I always drive.

Press and hold the DTC button for at least 3 seconds and you turn off DSC (Dynamic Stability Control) and DTC (Dynamic Traction Control) and now you're in TIM YOYO mode (That's It Motherf***er You’re On Your Own). I know most of us have already heard this and know this but it's still fun to say. I never really go there since I don't track and such and there's no point driving that way on the street, at least for me. Wrecked enough cars in my life and don't want to wreck this one.

[BMW135pls]

Just wanted to update the thread with my findings to this point. The intermittent noise which I found neat at first then quickly grew annoying has turned out to be early stages of a misfire on cyl6. When the noise occurred, it did not log a code, and did not trigger a limp mode. Replaced spark plugs and coil packs on all cylinders and have not experienced the sound since.