Excessive rasp from Bimmerworld X Pipe or is this normal?

[Vedubin01]

Originally Posted by MikeYQM

Which tune do you have?

Alpine stage 2

[94jedi]

I thought it was fairly well established that this was an issue w/ alpine stg 2 and forward x-pipes?

[Powashiftin]

Originally Posted by MikeYQM

Do you have the torque dip/bog/hesitation around 2500 RPM? Which tune do you have?

Yes. Alpine stage 2 (burble) from 2019. I just got two new maps from Alex. Stage 2 and stage 2 with burbles. I'll be changing to one of the new maps after I swap out my x pipe, return to oem tune and pass inspection.

The real question is ... why is anyone hanging around 2.5k RPM?

[tdott]

Originally Posted by Powashiftin

The real question is ... why is anyone hanging around 2.5k RPM?

For me, I don't notice it much driving on the street.

It is most apparent for me when launching the car at an autox event and trying to minimize wheel spin.

I try to get the car to roll off then hit WOT. So i'm in first accelerating and you feel right away when it hits ~2k-2.5k that the car stops accelerating for a split second then goes again.

If you just stab the throttle and launch it, it will just dump the clutch and light the rears up which isn't the fastest way to launch it.

This is a video of how I launch the car at an autox event. This was before my headers, so it doesn't do it in the video. Just giving you an idea of why it's a problem for some people.
https://photos.app.goo.gl/MAoB63yMamM7CwKn9

If I had video of it happening, you'd hear it sound like I lifted then hit the throttle again.
This is a video another guy with the problem captured on video:

[94jedi]

^ yea, that little hiccup is quite pronounced.

[tdott]

Originally Posted by 94jedi

I thought it was fairly well established that this was an issue w/ alpine stg 2 and forward x-pipes?

It is an issue on stock tunes also.

Its not unique to AlpineMS plus he confirmed that his tune doesn't have any changes below 3k rpm. Some BPM tuned owners also confirmed it was an issue for them.

Epic does the BW header tune and claims to be able to fix this.

[MikeYQM]

Epic Tune Successfully Tested

https://www.m3post.com/forums/showthread.php?t=1765810

[94jedi]

Originally Posted by tdott

It is an issue on stock tunes also.

Its not unique to AlpineMS plus he confirmed that his tune doesn't have any changes below 3k rpm. Some BPM tuned owners also confirmed it was an issue for them.

Epic does the BW header tune and claims to be able to fix this.

Looks like it's mainly Alpine tunes though. Glad to see he's stepping up to address this. Kudos to you and the others for driving a result here.

[MShift]

Originally Posted by MikeYQM

Epic Tune Successfully Tested

https://www.m3post.com/forums/showthread.php?t=1765810

I saw, planning to get the tune this week.

[cvstar9M3]

a couple years old, but op, where did you land on this? were you able to smooth out the rasp in the xpipe? I'm considering BW resonated xpipe.

[itoto]

Originally Posted by cvstar9M3

a couple years old, but op, where did you land on this? were you able to smooth out the rasp in the xpipe? I'm considering BW resonated xpipe.

I've dealt with this. I had the unresonated version. Rasp was pretty bad with quiet muffler (CNT Race muffler). I put a pair of vibrant resonators shortly after the x-merge, reduced rasp to about 10% of what it was. Paired with a less restrictive exhaust (modified the CNT) and the rasp was gone. So your options are to put more resonators or get a more free flowing exhaust.

One point though, I think the rasp experience is different between DCT and manual. DCTs also get the rasp when upshifting, i think the gear change in manuals are too slow to make the rasp when shifting.