[BMW DIY Guy]

Originally Posted by scarygary

I have mine pretty squared away as far as heatshield clearance, but theres still the vibration at 1500ish. Now I am thinking it might be the joints at midpipe and connecting pipes are not tightened properly, because the left over condensate is dripping onto garage floor.

Now THERE is an interesting idea, and one I forgot to add to my initial questions! The idea had crossed but slipped my mind!

If your cuts (mid to exhaust) have some gap AND the torca clamps are loose enough they can vibrate together, that would absolutely cause noise/feeling. Depending on gap, clamp strength, dirt in the gap, and other variables, it could absolutely only be an issue at certain RPMs or engine created vibration levels.

Great thought!

[atruong247]

Originally Posted by BMW DIY Guy

Hmm... wasn't my impression but again I didn't use a gauge on them either. I can check pretty easily considering I have my OEM mid (up in the garage rafters) and the single channel mid and ABs handy.

I would be rather surprised if they are "borderline flimsy" even in comparison, after handing them so many times. If I had a gauge I would measure for exact numbers.

Perhaps I have high expectations. If you see nothing wrong, then that's that. It'd be cool if we could get our hands on a schematic because making the el mp out of Ti would be cool.

[scarygary]

Originally Posted by BMW DIY Guy

Now THERE is an interesting idea, and one I forgot to add to my initial questions! The idea had crossed but slipped my mind!

If your cuts (mid to exhaust) have some gap AND the torca clamps are loose enough they can vibrate together, that would absolutely cause noise/feeling. Depending on gap, clamp strength, dirt in the gap, and other variables, it could absolutely only be an issue at certain RPMs or engine created vibration levels.

Great thought!

Mine at the connection you're referring to, the axleback pipes are touching the connector pipes. So I guess that could be it too. I was thinking it was at the spherical joints by the resonators, cant imagine those clamps tight enough to keep that joint from vibrating at some point. Also the thread on bolts at the torca clamp screwed up on mine, probably from over tightening.

[50shadesofhockenheim]

Originally Posted by CoffeeLife

The AA EL mid pipes can just produce a lot of rasp depending on the full setup (downpipes , rearbox combo) and I think people would be able to tell if its actually noise from rubbing on the frame or not.

If you listen to @50shadesofhockenheim on instagram it sounds pretty bad. I'm sure his was installed correctly....but if you listen to @am_m2c his sounds pretty good and clean.

Edit: had hockenheim_m2c earlier but was mistaken for 50shades

How does it sound bad? I don't have any vibrations or rasp

[BMW DIY Guy]

Originally Posted by 50shadesofhockenheim

How does it sound bad? I don't have any vibrations or rasp

Yeah this is exactly my question as a huge "why" child. I am not doubting those that have issues, but trying to understand WHY they have issues.

Some like you and I have no problems whatsoever, sounds great and is awesome. Some, from the videos, have real problems and I am trying to understand why.

There clearly are some variables involved.. install, fitment, clearances, what specific other components, and so on.

If it was always bad, I would say ok.. there is a product problem but that isn't the case. Since many folks, and would anecdotally say the majority of folks, don't have issues then its something about the install itself.

My hope is that if we can identify the variables we can find a common source of any rasp, and therefore can fix it for those (few?) that do have it.

Call me a raging type A.. *laugh* There are a few folks so passionate about this, that I would love to find a solution, since there are examples of it working perfectly. If yours/mine/others work fine, we can find what is different.

[50shadesofhockenheim]

Originally Posted by BMW DIY Guy

Yeah this is exactly my question as a huge "why" child. I am not doubting those that have issues, but trying to understand WHY they have issues.

Some like you and I have no problems whatsoever, sounds great and is awesome. Some, from the videos, have real problems and I am trying to understand why.

There clearly are some variables involved.. install, fitment, clearances, what specific other components, and so on.

If it was always bad, I would say ok.. there is a product problem but that isn't the case. Since many folks, and would anecdotally say the majority of folks, don't have issues then its something about the install itself.

My hope is that if we can identify the variables we can find a common source of any rasp, and therefore can fix it for those (few?) that do have it.

Call me a raging type A.. *laugh* There are a few folks so passionate about this, that I would love to find a solution, since there are examples of it working perfectly. If yours/mine/others work fine, we can find what is different.

It's because I am still on stock downpipes. It sounds bad when you go catless

[BMW DIY Guy]

Originally Posted by 50shadesofhockenheim

It's because I am still on stock downpipes. It sounds bad when you go catless

Hmmm.. I am catless.

[50shadesofhockenheim]

Originally Posted by BMW DIY Guy

Hmmm.. I am catless.

Have you posted a video? Also are you resonated EL?

[BMW DIY Guy]

Originally Posted by 50shadesofhockenheim

Have you posted a video? Also are you resonated EL?

The video isn't up yet, but will be soon. I am running (now) AA DPs, EL mid with resonated ABs and stock (non M Performance) exhaust.

I am working on an fully comprehensive comparison video for sound changes with midpipes.

Video will be the following configurations.

Component combinations:
1. Full stock OEM - downpipes, midpipe and exhaust

2. Stock downpipes, Active single channel midpipe with and without resonated AB pipes, and stock exhaust.

3. Active downpipes, Active single channel midpipe with and without resonated AB pipes, and stock exhaust.

4. Active downpipes, Active EL midpipe with resonated AB pipes, and stock exhaust.

[inTgr8r]

Originally Posted by 50shadesofhockenheim

How does it sound bad? I don't have any vibrations or rasp

In order to help get a handle on issues the various options need to be stated.
do you mind listing what is in your system?
- down pipes: OE , HF CATs, CATless
- Mid pipe: resonated or not
- back box?

I have done tons of exhaust work over the years, including working with a system fabricator doing test fitting etc.

In my experience the single biggest contributor to rasp is running HF CATs, or CATless.
To a lessor degree resonators design/elimination.
Vibrations, (especially those that are intermittent) are usually install related.
One of the biggest things that installers miss is the shift rearwards of the system with heat.

I have come across simple things like length of screws that make contact, only when hot.
I've also seen the same situation but opposite result, vibration when cold but goes away when hot.

In a nut shell there are lots of variables in play with a system that is designed within close tolerances and it doesn't take much to have an issue.

[BMW DIY Guy]

Originally Posted by inTgr8r

In order to help get a handle on issues the various options need to be stated.
do you mind listing what is in your system?
- down pipes: OE , HF CATs, CATless
- Mid pipe: resonated or not
- back box?

I have done tons of exhaust work over the years, including working with a system fabricator doing test fitting etc.

In my experience the single biggest contributor to rasp is running HF CATs, or CATless.
To a lessor degree resonators design/elimination.
Vibrations, (especially those that are intermittent) are usually install related.
One of the biggest things that installers miss is the shift rearwards of the system with heat.

I have come across simple things like length of screws that make contact, only when hot.
I've also seen the same situation but opposite result, vibration when cold but goes away when hot.

In a nut shell there are lots of variables in play with a system that is designed within close tolerances and it doesn't take much to have an issue.

Very very well said and exactly my thoughts as well.. I mean with my single channel install, I initially had HORRIBLE vibration right at a certain RPM simply because of a single bolt clearance. Found it, fixed it, zero issues after.

[50shadesofhockenheim]

Originally Posted by inTgr8r

In order to help get a handle on issues the various options need to be stated.
do you mind listing what is in your system?
- down pipes: OE , HF CATs, CATless
- Mid pipe: resonated or not
- back box?

I have done tons of exhaust work over the years, including working with a system fabricator doing test fitting etc.

In my experience the single biggest contributor to rasp is running HF CATs, or CATless.
To a lessor degree resonators design/elimination.
Vibrations, (especially those that are intermittent) are usually install related.
One of the biggest things that installers miss is the shift rearwards of the system with heat.

I have come across simple things like length of screws that make contact, only when hot.
I've also seen the same situation but opposite result, vibration when cold but goes away when hot.

In a nut shell there are lots of variables in play with a system that is designed within close tolerances and it doesn't take much to have an issue.

Non resonated EL midpipe. Everything else is stock. Active Autowerke themselves installed my midpipe

[inTgr8r]

Originally Posted by BMW DIY Guy

Very very well said and exactly my thoughts as well.. I mean with my single channel install, I initially had HORRIBLE vibration right at a certain RPM simply because of a single bolt clearance. Found it, fixed it, zero issues after.

Yes, that's that other thing that can happen.
A harmonic resonance can occur at a specific RPM and can be engine/drive train related.
The system will vibrate more at a specific resonance and make contact with that needle in the haystack screw.
You did well to find and isolate that!

That's also why you see resonance dampers on some OE systems.
Usually just a weight(s) clamped onto the pipes.

[CoffeeLife]

Originally Posted by 50shadesofhockenheim

How does it sound bad? I don't have any vibrations or rasp

Thats really good if its not heard in person. Some of the videos you post on your reel give off tinny / raspy sound.

[50shadesofhockenheim]

Originally Posted by CoffeeLife

Thats really good if its not heard in person. Some of the videos you post on your reel give off tinny / raspy sound.

Probably the videos when it's cold, it's extra loud for the first 30 seconds of driving. Apparently it's what our cars do when trying to heat the motor and exhaust. Something with cam timing and lots of fuel is what I was told lol. If you see any of the videos where I'm driving fast then that's when it's warm. I wouldn't beat on the car If cold

[StephGOD]

Originally Posted by BMW DIY Guy

Yeah this is exactly my question as a huge "why" child. I am not doubting those that have issues, but trying to understand WHY they have issues.

Some like you and I have no problems whatsoever, sounds great and is awesome. Some, from the videos, have real problems and I am trying to understand why.

There clearly are some variables involved.. install, fitment, clearances, what specific other components, and so on.

If it was always bad, I would say ok.. there is a product problem but that isn't the case. Since many folks, and would anecdotally say the majority of folks, don't have issues then its something about the install itself.

My hope is that if we can identify the variables we can find a common source of any rasp, and therefore can fix it for those (few?) that do have it.

Call me a raging type A.. *laugh* There are a few folks so passionate about this, that I would love to find a solution, since there are examples of it working perfectly. If yours/mine/others work fine, we can find what is different.

If you look at the initial poll I created awhile back you'll see that most people who voted actually do experience some form of the raspy sound issue at low RPM's. My guess is if you were to code Cold Start back on you would most likely experience this awful sound as well within the first few minutes of starting your car.

[BMW DIY Guy]

Originally Posted by StephGOD

If you look at the initial poll I created awhile back you'll see that most people who voted actually do experience some form of the raspy sound issue at low RPM's. My guess is if you were to code Cold Start back on you would most likely experience this awful sound as well within the first few minutes of starting your car.

yeah I appreciate your poll and read through that thread.

I am trying to understand though why this is the case.

[R0me]

Some notes.

I have gone through my decat, El res, and remus race backbox twice. And I have checked all bolts, loosened and tighten everything again, but to no avail. Still raspy at around 1500-2500 rpm when driving normal. It's raspy as soon as I drive, so heating and expansion should not do any difference. I have Coldstart coded out.

I can note that the choice of clamps between the two parts of the equal length is a peculiar one.

The clearance between the pipes at the crossover part is very small.

I believe the problem lies in the side of the exhaust that bends from the aft turbo. The exhaust speed is reduced because of induced turbulence in the pipe because the gasses mixes at each bend, and introduce disrupted flow. I think the evidence is that the bendy part is clearly much hotter than the straight pipe by looking at the colors. This could also mean the bendy part of the equal length expands more due to heat than the other straight part.


I find that the exhaust is less raspy with opened valves.

I believe all this just how my exhuast and the setup is ok. For example if I use the same the throttle input from 2500 to 3500 rpm, the exhaust doubles in volume when I hit 3000 rpm. Another thing is I can create an extremely loud reverberance if I floor it at 2500rpm and let go at 3000 rpm, sounds mental.
The sound also increases in volume when heated up.




Link here for sounds

[BMW DIY Guy]

Originally Posted by R0me

Some notes.

I have gone through my decat, El res, and remus race backbox twice. And I have checked all bolts, loosened and tighten everything again, but to no avail. Still raspy at around 1500-2500 rpm when driving normal. It's raspy as soon as I drive, so heating and expansion should not do any difference. I have Coldstart coded out.

I can note that the choice of clamps between the two parts of the equal length is a peculiar one.

The clearance between the pipes at the crossover part is very small.

I believe the problem lies in the side of the exhaust that bends from the aft turbo. The exhaust speed is reduced because of induced turbulence in the pipe because the gasses mixes at each bend, and introduce disrupted flow. I think the evidence is that the bendy part is clearly much hotter than the straight pipe by looking at the colors. This could also mean the bendy part of the equal length expands more due to heat than the other straight part.


I find that the exhaust is less raspy with opened valves.

I believe all this just how my exhuast and the setup is ok. For example if I use the same the throttle input from 2500 to 3500 rpm, the exhaust doubles in volume when I hit 3000 rpm. Another thing is I can create an extremely loud reverberance if I floor it at 2500rpm and let go at 3000 rpm, sounds mental.
The sound also increases in volume when heated up.




Link here for sounds

FANTASTIC write up, thank you for such detail and being so thorough! Its a very interesting thought that it could be gas speed down both pipes?

[ESB]

I'm very happy with my EL non-resonated despite admittedly not being 100% perfect.

Setup is:
-stock DP
-EL non-res
-stock muffler (non-M)

The only time I ever get bad sound is on some cold starts (meaning not 100% of the time). Likelihood goes up as overnight temps decrease (I park outdoors). Here is a video showing the issue (it will be even worse than this in Jan )

Other than that? Love the sound.

revs:

red lining:

boring driving at low revs:

With that said, I was disappointed last month to see I was a victim to a melted defuser. Confusing thing is that it took many months after install for it to happen... https://f87.bimmerpost.com/forums/sh...4&postcount=15

I also occasionally still get these vibrations, especially when making tight turns within the first minute or so of a cold start:

I realize that the melted diffuser and vibrations are due to install issues but I'm weary of taking it back to the shop since despite these issues I'm happy with the install since 99.9% of the time it sounds perfect (and the diffuser can't get unmelted...)

[BMW DIY Guy]

Originally Posted by ESB

I'm very happy with my EL non-resonated despite admittedly not being 100% perfect.

Setup is:
-stock DP
-EL non-res
-stock muffler (non-M)

The only time I ever get bad sound is on some cold starts (meaning not 100% of the time). Likelihood goes up as overnight temps decrease (I park outdoors). Here is a video showing the issue (it will be even worse than this in Jan )

Other than that? Love the sound.

revs:

red lining:

boring driving at low revs:

With that said, I was disappointed last month to see I was a victim to a melted defuser. Confusing thing is that it took many months after install for it to happen... https://f87.bimmerpost.com/forums/sh...4&postcount=15

I also occasionally still get these vibrations, especially when making tight turns within the first minute or so of a cold start:

I realize that the melted diffuser and vibrations are due to install issues but I'm weary of taking it back to the shop since despite these issues I'm happy with the install since 99.9% of the time it sounds perfect (and the diffuser can't get unmelted...)

Great post thank you and really sorry to hear about your diffuser! That sucks!!

Side note, I am in the Seattle area as well and done this install a ton.. need review of your fitment I can help. Shoot me a DM if so.

[BMW DIY Guy]

Originally Posted by atruong247

I'm sure youve held the midpipe in your hands. Not sure what gauge they are, but they are indeed thin and borderline flimsy. In comparison to the oem piping.

I have confirmation on pipe wall thickness, and the AA's are actually thicker than OEM, with caliper measurement.

OEM is 1.3mm
AA is 1.52mm

So I understand your concern on this point at least, but when measuring that is not the case.