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2015 operated differently. That goes beyond my personal experience but from what I've read the 2015 sport exhaust activates when you enter Sport (driving) mode.

Another (disappointing) thing is that a part of the sport exhaust sound enhancement is not directly to the exhaust but a sound chamber at the firewall to force sound into the cabin. Well, at least it isn't playing into the speaker system!!!

With everything that has been written about sport exhaust here I continue to become more confused. I had obtained certain beliefs from my salesman and the manual. It seems that either I misinterpreted or there is reason for the confusion.

And with that I open the discussion to those more knowledgeable than I.
 

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I did WaveTech's bypass and have NOT had any CELs, what I DID have, was that it disabled the econo start/stop function. I assume that it think's it's in Sport Mode (which automatically disables s/s). For me, this was a BONUS b/c I consider that a useless feature, and am annoyed that I have to press a button to deactivate it every single time I get in the car.
 

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Hi Guys,

1st post here but for a while on the Facebook group, and I believe some of you are there as well.

I really like the insight on this topic but I have one question that I'm not sure exactly how it works.

I have a 2017 with Performance Exhaust and there is a noticeable difference when the button is pressed in Conform and Sport+ or Race.

In confort it sounds louder than standard, the right side is working at any revs, but on upshifts it's kind of silent and down revving doesn't makes those nice burbles and pops as when the car is in sport. Is this all related to the indoor sound machine thing? To me it doesn't seem to be so, as there is a huge difference.

Most of the time, I'm casual driving and not WOT all the time so high revving upshifts is not the way to go but would love to have this for short sprints or overtakes etc. Is there any chance I can get this in Confort? Could it be possible with a tune?
 

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This topic has come up several times. The marketing in the DOGs has been deceptive IMHO. There is a non discussed firewall resonator box that brings noise into the cabin when the exhaust is activated. At least it isn't via the speakers!!!

Searching on Sport exhaust will bring up several posts. One for instance is ...

 

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Hm, I was checking my car and it says I have U21, but I don't have the exhaust button on the dash though. This is a 2015 model.
Does that mean I have the upgraded exhaust or the normal one?
+1

I also searching how the exhaust valve work on my 2014 gla 45 amg . Any idea ?
It seems to be more simple like confort : closed . Sport or manual : open. (From what I read here and there)
But I'm facing some different behaviour at this time ... (Most of the time open) if anybody have precise description ?
 

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After few test this morning I can reply to my question.

Confort mode : valve open at idle . close when accelerate stay close at any rpm over around 1500rpm.

Sport mode : valve open at idle. close when accelerate and reopen over 3500rpm (something like this)
 

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yah back pressure is important, that why i plugged the valve back. straight pipe fix is not desirable .
 
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I just checked the part numbers for the exhaust without U21 and the one with U21, and they're different.
The sound port with the piping are a different system with a different part number.
So while the button may indeed only activate the sound port in the firewall and that statement that the OP made is correct, the other statement that the OP made, namely that the exhaust piping is identical, with or without U21, is completely wrong.
The two exhausts are constructionally different.
Oh BTW, I also had a WRX before, mine was twinscroll, an imported engine, long story, a 3" exhaust, once you got past the twinscroll resonant drone with a proper resonator, was beautiful.
 
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