2017 F-Type R Coupe daily driver 30k miles

I’m still trying to track down why after warm up, my exhaust sound has become somewhat more muted than than it used to be. I always drive in dynamic mode with sport engaged on the shifter, and a large percentage of the time I’m using the paddle shifters.

I have not had any of the reported exhaust patches applied which have been discussed in other threads that take away pops and crackles. I still can modulate as many machine gun type crackles at will.

I’ve verified that exhaust valves, that can be seen through the tailpipes, are opening and closing correctly, and when I close them, there is a huge difference in how much the exhaust note is muted.

The Mystery is this: When I’m idling and reving the engine in the driveway (with my door open)where I can really hear the exhaust, I’ve noticed that there seems to be an additional stage of open/close muting besides the valves in the back. Example: I’m idling in full dynamic mode...now I use the switch to take it out of dynamic, and of course as it should, the exhaust button light goes out telling me the valves are closed..the sound is very muted. Next is the interesting part. I press the exhaust button and open up the valves, the note becomes less muted. (Note: I’m still not in dynamic mode) Now, when I engage dynamic mode switch (remember, the valves are already open) there is a secondary increase in volume and depth of the exhaust note. So my question is, what else in the exhaust chain is opening up? If I can ascertain this, perhaps I can identify why my exhaust is sound more muted than before. Maybe it’s something to do with whatever this secondary stage thing is? Also, or... could it be the catalytic convertors getting clogged or starting to go bad? I have had no codes, or smoke from tailpipes, but maybe they are clogged enough to change the exhaust sound??

CORRECTION: See my Post response to SCM which says: "your right in that in Dynamic mode the exhaust light is on (lighted), Dynamic mode off and everything is off. (I'll have to modify my original post) Here's what I didn'tknow until I just double checked. With Dynamic mode OFF, if I then just hit the muffler switch(with lights up), only the passenger side valve opens to add a little more sound (as designed I guess) When I activate Dynamic mode, BOTH sides are open, and so that must be the sound difference I'm hearing between Dynamic + exhaust switch on... and Dynamicoff + exhaust switch on. So now the only part of my question that is still valid is whether the CATs starting to get clogged will alter and slightly mute the overall sound, making it more muted than it was when the car has less miles on it?

I really apologize for the long and very clumsy explanation of what I’m hearing, but I miss my exhaust sound when the car was newer.
CRS

 

My MY18 doesn't work as you describe, so different MYs have different characteristics.

In mine, when idling, switching dynamic on lights the exhaust switch and opens the valves so you get the grumble. out of dynamic mode with the switch on doesn't open the valves - the valves don't actually start opening until around 1,500 rpm, you can definitely hear the difference if you then switch dynamic back on. Hold the revs above 1,500 and play with the exhaust switch to see how it behaves.

As I mentioned, other MYs are different, some open the valves at idle out of dynamic mode, these cars have had many subtle changes throught he build years!

 

I drive in dynamic mode all the time and I have both fuse 43 and vacuum lines pulled, sometimes the car still goes into quite mode, albeit rarely, ie low sound except near WOT and muffled pops(instead of popping it sounds like water bubbling). To this date I cannot figure out why.

 

Arrgg....your right in that in Dynamic mode the exhaust switch light is on , Dynamic mode off and everything is off. (I'll have to modify my original post) Here's what I didn't know until I just double checked. With Dynamic mod OFF, if I then just hit the muffler switch, only the passenger side valve opens to add a little more sound (as designed I guess) When I activate Dynamic mode, BOTH sides are open, and so that must be the sound difference I'm hearing between Dynamic + exhaust switch on... and Dynamic off + exhaust switch on. So now the only part of my question thats still valid is: Will the CATs starting to get clogged will alter the overall sound...making it more muted than it was originally ?

 

Something is wrong. The two valves are connected to the same vacuum line, so if they aren’t opening and closing together all the time, one of them is sticking.

 

So...when I toggle the Dynamic lever to activate dynamic mode, Both valves are open. Toggle dynamic off, and both valves close. BUT, if I Toggle Dynamic mode off (closing both valves) and then just press the exhaust button, only the passenger valve opens. If I then Toggle the Dynamic lever to activate dynamic mode, both valves are again open.

The partially muted symptoms I'm describing are while I'm in full dynamic mode, with shifter set to sport. The setting I've use pretty much 100% of the time for the 3.5 years I've driven the car.

I've checked multiple times (while in full dynamic mode) by pulling over to the side of the road, putting the car in park and I observe both valves fully open while idling. I've checked a couple time because I could swear that they were partially closed by what I perceive as a more muted than normal sound...but each time they are fully open. Unless somehow the valves are intermittent while driving (which I have no way to visually check) Like maybe they are partially closing when I'm driving? It's crazy making! :-) Thats why I was wondering if dirty Catalytic convertors maybe had anything to do with the muted sound.
BTW : MY17 R Coupe. Thanks for any insight Unhinged
CRS

 

Exhaust valves are not designed to operate independently as already mentioned. The fact the your car can means one of the valves is starting to stick. I suspect the different modes(dynamic vs non-dynamic with exhaust on) probably create similar but slightly different vacuum pressures that may not be high enough to open the valves fully. The sticky valve requiring higher pressure than an non-Sticky valve to open so hence is affected first once the pressure becomes suboptimal. Also would explain partial opening at times . A leak in the vacuum pipe or fitting coming loose may be the issue in theory. And of course fixing the sticky valve too

 

It’s unlikely that the issue is a leaking vacuum line, as the vacuum lines for each of the valves are not isolated. A leak would affect both valves equally. A sticky valve is most likely.

 

Thanks for the clarification. The car goes in for it’s annual service in about a month. I’ll have them run a diagnostic on the vacuum lines and valve components. The car is still under warranty so if there is any doubt, I’d love to have them just replace the whole exhaust unit...since my understanding is that the valves cannot be replaced independent of the whole system.. Question: Are the CATs included in a new exhaust system? I wish I understood better how the entire vacuum worked. Does anyone have a schematic that a non mechanic like myself could get a better idea of the system?
Thanks
CRS

 

Agreed A sticky valve is a given. , All i meant to say is that it is going to manifest itself first on the sticky valve as the sticky valve is going to require higher vacuum pressure to activate when valves are exposed to the same vacuum pressure., and that there is obviously a subtle but different pressure in the system depending on what driving mode is engaged to explain the poster's observation

 

I think your MY uses engine vacuum rather than the electric vacuum pump. This is from 2013...
https://www.dropbox.com/s/szc3vze5ol...haust.pdf?dl=0

 

Thank you. Yes, you are correct.