Equal-length exhaust discussion: new S55 sounds

[Trevorstein]

Originally Posted by rborane

For what its worth, I have catless downpipes and noticed zero gains from OEM downpipes, both using BM3 stage 1 tune. No interest in running the stage 2 tune as most of the gains are up to stage 1 and it is plenty fast for me. Catless downpipes made it louder, and increased the rasp.

My plans now are to put OEM downpipes back in, and replace the secondary cats with Vibrant 1792 resonators. Also thinking of replacing the OEM resonator with a X-Pipe to add some volume, but I believe the OEM resonator is an H-Pipe, correct? Any suggestions on what to do with the OEM resonator? I am keeping the OEM midpipe and definitely replacing the secondary cats with Vibrant 1792's.

Good plan!

The OEM Resonator box holds a (smaller diameter) very restrictive "H-pipe" inside.

Here's what I did. It sounds very good! Except at start up (cold - valves closed) a bit of "rasp".



No drone at all though, that I can notice at high end.

If I were to try the ELE solution, I'd replace that "X-pipe" with straight tubing and install it ("X-pipe")
further back, transversely behind the differential in order to merge the pipes, after the 14" extension,
to lead these into each side of the stock ZCP muffler.


Cheers!

[rborane]

Originally Posted by Trevorstein

Good plan!

The OEM Resonator box holds a (smaller diameter) very restrictive "H-pipe" inside.

Here's what I did. It sounds very good! Except at start up (cold - valves closed) a bit of "rasp".



No drone at all though, that I can notice at high end.

If I were to try the ELE solution, I'd replace that "X-pipe" with straight tubing and install it ("X-pipe")
further back, transversely behind the differential in order to merge the pipes, after the 14" extension,
to lead these into each side of the stock ZCP muffler.


Cheers!

Nice! What resonators and X-pipe is that? Any sounds clips I can refer back to that you may have posted for this setup?

[Trevorstein]

Originally Posted by rborane

Nice! What resonators and X-pipe is that? Any sounds clips I can refer back to that you may have posted for this setup?

Hey,

Thanks!

Since you really can't avoid, "Made in China" - I tried. There's Burns Stainless but,
you may as well have Akrapovic fabricate you a full custom exhaust for what they're charging...

I went with 304 SS!

* Vibrants
* Summit Racing (house brand) - Not really much of an actual "X" internally but (both items)
very well fabricated and finished.

I do have a sound clip but, It's not that aggressive. + How do I upload an MP4??



Cheers!

[RevNev]

Originally Posted by Montaver

I don't think cats are 'cool', I think they are necessary. Driving behind a fully catless car with the windows down is awful. The idea that because there are cars without cats on the road, so why bother having them on mine is a straw man. I guess I shouldn't bother recycling because not everything is recycled, so why should I? I guess I shouldn't bother wearing a mask during COVID because not everyone wears one, so why should I? Also there are plenty of states in the US where there is barely any emissions testing, Australia is not unique in that regard.

Your video sounds like every other S55 with less rasp. You made a midpipe with resonators, now your trying to sell everyone else on it. Revolutionary stuff.

I'm no environmentalist and I'm not interested in it either with a car I'm lucky to drive once a fortnight. You've heard a video from a phone taped to the rear bumper but you need to hear the car in the flesh as I have and let me tell you, it sounds nothing like the typical S55. I've already had those typical exhausts on the car, didn't like the note and made my own midpipe.

The fact is, no one does a sufficiently resonated midpipe otherwise I would have bought one instead crawling around on the floor under the car making one. Revolutionary in the sense that I added resonators and the aftermarket mainstream delete them to emphasise the rasp and maximise the unequal length S55 farty note.

Anyway, that's what I did with my exhaust and if you don't like it, do something else or leave it stock who cares

[doughboy]

Originally Posted by drgmt

Great work.

I think it sounds much better if you merge into a single pipe then split. Was there any room to do that ?

I know a merge to single pipe would sound better (splitting after single pipe is irrelavent and for looks only), but budget, time and space say otherwise so I'm with standard rear muffler and there's no room to do it.

I'm really happy with it, OE look, valves closed the standard muffler has plenty of muffling and EL gives it lovely deep smooth sound, especially at lower speed, but the valves open it has hardly any silencing so a rasp comes in 4-5k but clears up after 5, but with the equal length at least the rasp is "harmonious" if that makes sense!

I intend to get more mufflers in there when the lockdown is done, but for now all good.

[RevNev]

Originally Posted by Trevorstein

Good plan!

The OEM Resonator box holds a (smaller diameter) very restrictive "H-pipe" inside.

No it's not restrictive at all. The problem is, it's not packed with anything and acts as an echo chamber emphasising the raspiness. I'd pack the stock resonator with stainless wool, but it's pretty small to be overly effective.

[Kilabyte]

Originally Posted by RevNev

I had a good fiddle with various combos after sourcing 2 stock ZCP exhaust systems I could chop up and leave my original in tact. This is the best note I discovered by far retaining the stock "unequal length" scenario. Raspiness is the hardest tone to minimise on this engine the 4 resonators packed with stainless wool addressed most effectively. Fibreglass and needle mat packing I also tried lowered the pitch too much and sounded as if it was revving to 5000 when it was spinning to 7000rpm.

Which resonators do you recommend? I did a quick search and it seems like most places don't disclose what they're packed with.

[Trevorstein]

Originally Posted by RevNev

No it's not restrictive at all. The problem is, it's not packed with anything and acts as an echo chamber emphasising the raspiness. I'd pack the stock resonator with stainless wool, but it's pretty small to be overly effective.

I did not open mine up. I had just seen photos of others and they looked much smaller.


Cheers!

[RevNev]

Originally Posted by Kilabyte

Which resonators do you recommend? I did a quick search and it seems like most places don't disclose what they're packed with.

I couldn't source any resonators the right size and construction and had to fabricate them. They're 12 inches long, 4" diameter perforated tube packed with stainless wool.

[Trevorstein]

Vibrant #1792 304 SS Bottle Nose Resonator -

* https://vibrantperformance.com/catal...974e31ed211250

[soobieajax325]

I’ve read quite a few pages already. But not all.
I should good to go if i add 14” of piping to the passenger side of my AWE resonated exhaust system? Or do i have to add an x or h pipe?

[ntg44]

Originally Posted by soobieajax325

I’ve read quite a few pages already. But not all.
I should good to go if i add 14” of piping to the passenger side of my AWE resonated exhaust system? Or do i have to add an x or h pipe?

https://f80.bimmerpost.com/forums/sh...&postcount=919

[soobieajax325]

Originally Posted by Euromotive Performance

we're gonna try to make it as compatible as possible or offer as many options, such as a resonated and non resonated version and an F87 counterpart soon too.

I have an AWE resonated version and would be interested as well

[Velon]

Originally Posted by RevNev

I couldn't source any resonators the right size and construction and had to fabricate them. They're 12 inches long, 4" diameter perforated tube packed with stainless wool.

Is 12" the longest you can fit where the stock resonator fits? Gonna get me either the 12" model or the 18" of the Vibrant performance resonator.

[RevNev]

Originally Posted by Velon

Is 12" the longest you can fit where the stock resonator fits? Gonna get me either the 12" model or the 18" of the Vibrant performance resonator.

You won't fit 18" resonators in there to take the pipework over the trans tunnel brace. 12"x 4" side by side is about the longest that fits the space.

[behindthen0thing]

Originally Posted by RevNev

You won't fit 18" resonators in there to take the pipework over the trans tunnel brace. 12"x 4" side by side is about the longest that fits the space.

theres some trans braces that are made that have extra clearance.
I wonder if this would allow for an 18 " resonator installed.

[RevNev]

Originally Posted by behindthen0thing

theres some trans braces that are made that have extra clearance.
I wonder if this would allow for an 18 " resonator installed.

14" would be maximum length if you tightened the bends on the front section before the resonators, but I think 18's are just too long for the available space.

The other problem with resonators in the secondary cat location is heat burning out fibreglass packing. We've got resonators in Australia called "Hot Dogs" like "Cherry Bombs or Glasspacks" they call them in the US, but the packing burns out fast when close to the engine. Stainless wool doesn't burn out, but it's not used often in shelf resonators and it's another reason I made my own.

[_Timm3]

Originally Posted by RevNev

14" would be maximum length if you tightened the bends on the front section before the resonators, but I think 18's are just too long for the available space.

The other problem with resonators in the secondary cat location is heat burning out fibreglass packing. We've got resonators in Australia called "Hot Dogs" like "Cherry Bombs or Glasspacks" they call them in the US, but the packing burns out fast when close to the engine. Stainless wool doesn't burn out, but it's not used often in shelf resonators and it's another reason I made my own.

I haven't heard the term Cherry Bombs or Glasspacks since the late 90's early 2000's I had one on my VW back in the day. Do they still make those? Anyways, waiting to hear/see Euromotive's EQ solution.

[X.X.I.V]

Originally Posted by David@ActiveAutowerke

In order to take care and preserve the health of our staff we decided to shut down the workshop until April 20th. We're still processing online orders and have limited phone/support hours running a limited office staff, but no work in the shop will resume for a couple weeks.

Bump for AA, you guys still closed ?

[Vulpe]

Originally Posted by X.X.I.V

Bump for AA, you guys still closed ?

I've seen them posting regularly on Instagram. Nothing about the midpipe from what I've seen though.

I am interested in their EL Mid but also curious about how there's no resonators in it to kill the rasp which is the main thing I want eliminated.. Also I have an M2C so I hope these solutions turn into M2 versions by the end of the year.

[RevNev]

Originally Posted by Vulpe

I've seen them posting regularly on Instagram. Nothing about the midpipe from what I've seen though.

I am interested in their EL Mid but also curious about how there's no resonators in it to kill the rasp which is the main thing I want eliminated.. Also I have an M2C so I hope these solutions turn into M2 versions by the end of the year.

You can't kill the rasp with an un-resonated midpipe keeping in mind with valves open other than perhaps the primary cats to dampen noise, the exhaust is virtually unmuffled. Exhausts with no mufflers/resonators sound lousy on any car and engine combo.

The S55 is no raspier than any other engine if the exhaust is resonated effectively but the problem is, they're all deleting midpipe resonators instead of adding them to eliminate the rasp.

[iPod]

Hi all,

Just received and installed the new Milltek Equal Length exhaust. I've made a video to compare with My UK spec M4 Competition :

Stock downpipes - OEM Exhaust
Stock downpipes - Secondary cats delete - Milltek Resonated Exhaust
Stock downpipes - Secondary cats delete - Milltek Equal Length Exaust

https://youtu.be/vRjrLI1lewg



As you can see there is no merging of the pipes after the length equalization. Adding the extra length on it's own does however change the sound as you can see on the video, mostly on the road under load at mid and high rpm. Low rpm are not really affected and I'm actually very happy with that as I didn't want to loose the specific S55 sound totally !

My setup is not ideal as the secondary cats have been replaced by tubes and I have a huge resonance at 3-4k rpm. This setup really require an extra set of resonators where the secondary cats are.

This is now way to loud for my liking so I'll be putting back the secondary cats next week and it should hopefully calm the resonance down at 3-4k rpm !