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      12-09-2019, 03:38 PM   #67
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Just a thought..

Is there any mixing of the left / right gas streams inside the OE rear silencer or are they fully isolated from each other?

Is having a H or X pipe even required? As it's turbocharged we don't have any pressure pulse scavenging effects like a naturally aspirated engine to worry about, we are only interested in sound.
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      12-09-2019, 03:45 PM   #68
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Quote:
Originally Posted by doughboy View Post
Just a thought..

Is there any mixing of the left / right gas streams inside the OE rear silencer or are they fully isolated from each other?

Is having a H or X pipe even required? As it's turbocharged we don't have any pressure pulse scavenging effects like a naturally aspirated engine to worry about, we are only interested in sound.
That's been thought of before. The problem you run into is with valves open you'll get minimal merge end it'll sound like garbage. That's why it's such a challenge with stock muffler.
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      12-09-2019, 03:58 PM   #69
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Thanks.

So unmerged pipes will sound bad, even if equal length?

I'll be keeping secondary CATs for emission checks as I'm going decat DPs but will look to replace OE centre box / H pipe with two separate mufflers before adding the equalizing length.

Just considering options for rear box.

I have an M2 competition by the way, so i need to get it on a ramp and measure lengths accurately.
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      12-09-2019, 04:09 PM   #70
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Quote:
Originally Posted by doughboy View Post
Thanks.

So unmerged pipes will sound bad, even if equal length?

I'll be keeping secondary CATs for emission checks as I'm going decat DPs but will look to replace OE centre box / H pipe with two separate mufflers before adding the equalizing length.

Just considering options for rear box.
If left unmerged, may as well keep the lengths as is. There won't be a difference in tone without an equal length merge.

But if you're going with 2 mufflers, just stick with my design and make the return of the U bend earlier, and make another 90 degree pipe bend at the center of the car. Then split with T pipe, attach the mufflers, and route both sides out the back. With a dual exit you don't need as big of mufflers anyways.
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      12-09-2019, 05:02 PM   #71
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yep, basically without the merge, it will sound like two 3-cylinder engines competing for noise, basically how a stock car or aftermarket mid-piped car sounds like currently.

as for the stock muffler design, there is little merging effects on it, both sides are independent of each other (meaning there isn't a crossover effect as the pulses never meet each other).

On that note, I do wonder how the importance it is to even remove the OE crossover section, technically since the flow through there already contains un-equally spaced pulses flowing through the crossover, would it even matter to delete this entirely? Couldn't you just leave that on there and run the U-bend and re-merge them again in equally spaced pulses after that section and achieve the same result? Since the waves are all traveling at the same rate, that would tell me that the OE crossover section wouldn't even impact the sound quality we are after because you can still evenly space them and merge them at the back of the differential.

Just a thought in case anyone wants to try something 'new' compared to a what I or a few of us did


Here are my prototype pics, they aren't pretty looking (warning...)

CLICK ME
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Last edited by spool twice; 12-09-2019 at 05:57 PM..
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      12-09-2019, 05:49 PM   #72
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So beyond the custom piping you guys have done, what's the latest on an actual product that may be available to market soon?

Barring that, anyone in the North West Region know of a good exhaust fabricator?
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      12-09-2019, 06:45 PM   #73
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Quote:
Originally Posted by two+2 View Post
So beyond the custom piping you guys have done, what's the latest on an actual product that may be available to market soon
Oh boy, do I have some news for you (and everyone else)

I'm currently buttoning up a few last things with my exhaust, but I've been permitted to share the following:

Thanks to the success of my exhaust experiment, along with the momentum that's been building here on the forum, I've been informed that TopGear Motorworks is pursuing a dual exit, valved, production version of my exhaust! In early January, My M3 will be entering the shop for development of a production system.

That's all I can share for now. Obviously, nothing is set in stone, and everything is always subject to change. But to think that this project even got this far, to even be considered as more than just one guy willing to spend some money to fix his car's exhaust sound, is a testament to the enthusiasm of this community and the lengths we're willing to go to to push the platform forward. I'm just as excited as everyone else, and all I have left to say is be patient everyone - the future of S55 exhausts could be here sooner than we think!
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      12-09-2019, 07:09 PM   #74
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Hell yes! That's awesome.

Quote:
Originally Posted by ntg44 View Post
Oh boy, do I have some news for you (and everyone else)

I'm currently buttoning up a few last things with my exhaust, but I've been permitted to share the following:

Thanks to the success of my exhaust experiment, along with the momentum that's been building here on the forum, I've been informed that TopGear Motorworks is pursuing a dual exit, valved, production version of my exhaust! In early January, My M3 will be entering the shop for development of a production system.

That's all I can share for now. Obviously, nothing is set in stone, and everything is always subject to change. But to think that this project even got this far, to even be considered as more than just one guy willing to spend some money to fix his car's exhaust sound, is a testament to the enthusiasm of this community and the lengths we're willing to go to to push the platform forward. I'm just as excited as everyone else, and all I have left to say is be patient everyone - the future of S55 exhausts could be here sooner than we think!
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      12-09-2019, 08:43 PM   #75
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Quote:
Originally Posted by ntg44 View Post
Oh boy, do I have some news for you (and everyone else)

I'm currently buttoning up a few last things with my exhaust, but I've been permitted to share the following:

Thanks to the success of my exhaust experiment, along with the momentum that's been building here on the forum, I've been informed that TopGear Motorworks is pursuing a dual exit, valved, production version of my exhaust! In early January, My M3 will be entering the shop for development of a production system.

That's all I can share for now. Obviously, nothing is set in stone, and everything is always subject to change. But to think that this project even got this far, to even be considered as more than just one guy willing to spend some money to fix his car's exhaust sound, is a testament to the enthusiasm of this community and the lengths we're willing to go to to push the platform forward. I'm just as excited as everyone else, and all I have left to say is be patient everyone - the future of S55 exhausts could be here sooner than we think!
What are the chances of an M2C version? Need someone there to offer a car for testing! Would offer mine but I'm based in NYC.
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      12-09-2019, 09:28 PM   #76
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Any thoughts if a 3.5" and a 2.5" pipe will fit for a short distance somewhere up front?
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      12-10-2019, 01:17 AM   #77
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Quote:
Originally Posted by spool twice View Post

Here are my prototype pics, they aren't pretty looking (warning...)

CLICK ME
I thought the point was to have equal length before and after the merge?
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      12-10-2019, 06:02 AM   #78
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Quote:
Originally Posted by Frode D View Post
I thought the point was to have equal length before and after the merge?
Nope, after they merge or crossover in equally spaced pulses, you can do whatever you please with the exhaust.
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      12-10-2019, 07:19 AM   #79
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Quote:
Originally Posted by spool twice View Post
yep, basically without the merge, it will sound like two 3-cylinder engines competing for noise, basically how a stock car or aftermarket mid-piped car sounds like currently.
OK I get that, but I was thinking that without a merge in the piping the "merge" would be the atmosphere when the pulses leave the tailpipes, where we actually hear the sound from.

So as long as they left the tailpipes in sync??

Firing order is 153624, which is bank 1,2,1,2,1,2 in order, so pulses should emerge from tailpipes left, right, left, right etc.

All theory....
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      12-10-2019, 07:28 AM   #80
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It wouldn't work that way, coming from a car that had fully equal-length left/right pipes (but without a crossover), adding a crossover changed it from two 3 cylinder sounds to a true V6 sound on my Audi S5. The idea is to have all cylinder exhaust pulses in each pipe to create the sound.

You are correct with the crossover though, it doesn't do much for forced induction applications for scavenging so it's location would not matter as much as a naturally aspirated car. It impacts more of sound quality coming out the tailpipes than anything else.

Good luck to you on the pipes! I hope you don't have inspections like that German guy who has to go through inspections each year, sounds tough to get modifications done in Europe.
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      12-10-2019, 10:08 AM   #81
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Quote:
Originally Posted by spool twice View Post
Good luck to you on the pipes! I hope you don't have inspections like that German guy who has to go through inspections each year, sounds tough to get modifications done in Europe.
Thanks, I think might go more down ntg44 style but with a made up 4-exit single silencer rather than his single exit (although I do love the JDM style).

Less room behind the diff on an M2 comp than an M3/M4

UK mods are not too bad, no inspections for 3 years on a new car. Then I can pass the emissions test with only secondary CATs fitted thats why I want to keep them and go Decat primary.

I did the same with my N54 335i, passed OK.
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      12-10-2019, 01:42 PM   #82
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ntg44

I probably should know this, but I don't since I hadn't planned on removing my cats, but do you get any warnings with removing the secondary cats?

Also would the production exhaust be with or without the cats?
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      12-10-2019, 01:46 PM   #83
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Quote:
Originally Posted by EvoFire View Post
ntg44

I probably should know this, but I don't since I hadn't planned on removing my cats, but do you get any warnings with removing the secondary cats?

Also would the production exhaust be with or without the cats?
No CEL or any codes with secondary cat delete.

In lieu of calling this a "cat back" exhaust, to be clear, this exhaust will be bolt on from the stock downpipe connection -> back.
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      12-10-2019, 04:32 PM   #84
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Quote:
Originally Posted by ntg44 View Post
Oh boy, do I have some news for you (and everyone else)

I'm currently buttoning up a few last things with my exhaust, but I've been permitted to share the following:

Thanks to the success of my exhaust experiment, along with the momentum that's been building here on the forum, I've been informed that TopGear Motorworks is pursuing a dual exit, valved, production version of my exhaust! In early January, My M3 will be entering the shop for development of a production system.

That's all I can share for now. Obviously, nothing is set in stone, and everything is always subject to change. But to think that this project even got this far, to even be considered as more than just one guy willing to spend some money to fix his car's exhaust sound, is a testament to the enthusiasm of this community and the lengths we're willing to go to to push the platform forward. I'm just as excited as everyone else, and all I have left to say is be patient everyone - the future of S55 exhausts could be here sooner than we think!

I will be one of the first people in Germany who will order this exhaust system immediately after launching it
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      12-10-2019, 05:35 PM   #85
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Quote:
Originally Posted by ntg44 View Post
Oh boy, do I have some news for you (and everyone else)

I'm currently buttoning up a few last things with my exhaust, but I've been permitted to share the following:

Thanks to the success of my exhaust experiment, along with the momentum that's been building here on the forum, I've been informed that TopGear Motorworks is pursuing a dual exit, valved, production version of my exhaust! In early January, My M3 will be entering the shop for development of a production system.

That's all I can share for now. Obviously, nothing is set in stone, and everything is always subject to change. But to think that this project even got this far, to even be considered as more than just one guy willing to spend some money to fix his car's exhaust sound, is a testament to the enthusiasm of this community and the lengths we're willing to go to to push the platform forward. I'm just as excited as everyone else, and all I have left to say is be patient everyone - the future of S55 exhausts could be here sooner than we think!
Congratulations, this is awesome news for you and the community! I'm ready to commit to the group buy already!! Took the midpipe off my Xmas shopping list for this bad boy

Last edited by Redacre; 12-10-2019 at 05:41 PM..
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      12-10-2019, 05:46 PM   #86
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Quote:
Originally Posted by Redacre View Post
Congratulations, this is awesome news for you and the community! I'm ready to commit to the group buy already, but can I ask if this will be compatible with aftermarket midpipes like AA? I'm thinking I should adjust my Xmas shopping list
This exhaust will be a replacement for AA mid and the muffler. No sense in buying both.

Just for the record, there's nothing for sale, and I will not be advertising anything related to the sale of this exhaust. I'm not a vendor, just a customer who is loaning his car for the development.
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      12-10-2019, 06:48 PM   #87
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AA midpipe? Mating any equal-lengthed system after this midpipe wouldn't make a difference, and won't even come close to the sound quality when mated to that system or the VRSF single midpipe because they merge un-equally spaced pulses (read: they don't resolve the issue with the S55 sound and don't break any new ground).

If you do an equal-length design, those two pipes (or any midpipe that has a crossover) becomes paper weight, it's the harsh reality of it unfortunately.

Last edited by spool twice; 12-10-2019 at 09:03 PM..
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      12-11-2019, 05:24 AM   #88
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Quote:
Originally Posted by ///mpower.nick View Post
He added a 14" Custom bended pipe and a flowmaster X pipe. I'm doing this same mod as it's one of best sounding exhausts I heard. I'm curious on how the magnaflow race mufflers that'll replace the secondary cats will sound. Probably clean up the sound a bit. I'm looking to have a normal maybe somewhat louder exhaust when valves are closed and an absolute monster with great tone when open. Spool twice has the closest tone I'm looking for, NTG exhaust also sounds really nice. Pretty amazing what they've done that heavy hitter exhaust companies couldn't do.
Just as a forewarning, you will likely get a "wtf" look or a confused facial gesture when you ask an exhaust shop to accomplish this. I had to go to a few, and the one that finally did it was still hesitant and kept saying "In all my 15 years of building an exhaust, adding just an x-pipe will do the same thing".... it won't do the same thing. Just keep insisting on it and just say "if it doesn't accomplish what I want, I can always return it back to stock."

It's an outside-the-box approach to resolve the space constraints.

Last edited by spool twice; 12-11-2019 at 05:33 AM..
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