Good morning, I'm wondering if anyone else has this problem? It seems that my exhaust system has a mind of its own, even when all settings are correct for sport exhaust it seems that it can go into stealth mode on its own while driving. I owned a 2015 Z51 A8 and never had this problem this car is a 2016 Z06 M7. It started happening yesterday when driving home from work so not sure if this is a one time thing or something that is starting to go wrong. Figured I would start here before I bring it in for service.

 

If you put it to tack does it get louder? There is a difference between sport and track mode in how the exhaust operates.

I have not figured it out completely. But it does shift from quiet to loud and back in sport.

 

I will try that later today. Thanks

 

Does it switch to stealth on the SETTINGS screen, or do you just hear the exhaust pitch change? The pitch changes on mine in SPORT mode.....I assume it is the prgramming. But it stays in whatever mode I set it to. As a result, I don't use SPORT mode. If I want loud, it is TRACK mode, if I want quiet, it is TOUR or STEALTH.

At some point there was a thread that explained the difference between SPORT and TRACK mode.....

 

Just sound changes so I guess track mode is the setting if you want it loud all the time

 

Even in track mode it will go quiet under certain conditions. Normal.

 

The 7 speed manual will not go quiet in track mode. The auto will under certain conditions.

 

The only negative I've noticed is that if you are in Track Mode and turn the car off, it will restart in Tour mode, which sucks. I wish it would revert back to Sport Mode or stay in Track Mode that would be great...It only does this in Track Mode...maybe it's a safety thing...but it's annoying.

 

That has been my observation as well on the A8

 

Here is a write-up on how the NPP and AFM valves work between the M7 & A8.

1. All C7 have valves for V4 mode in front of the mufflers. We call them AFM valves. Fuse 32 controls the AFM valves, and pulling fuse 32 or AFM connectors will result in a CEL and awful sound in V4 mode.
2. NPP cars have electronic valves in the outer exhaust tips. We call them NPP valves. Fuse 41 (2014) or fuse 42 (2015) controls NPP valves. Pulling the fuse will NOT cause a CEL, nor will pulling the connectors at the valves. These two NPP valve disable methods are electrically identical, but the fuse pull is simpler and more easily reversible.
3. Manual transmission cars go into V4 mode ONLY in ECO mode.
4. Automatic cars go into V4 mode in ALL MODES, except when paddle shifting/sport shift.
5. Driving Mode (dial) does affect NPP behavior with Engine Sound Management (ESM) ON. However, that's subject to most of the below when OFF.
6. Driving Mode does not alter sound with NPP valves and AFM valves OPEN (V8 operation). This is the loudest the NPP exhaust can be, and Driving Mode doesn't change the sound when both sets of valves are open.
7. Engine Sound Management (ESM) OFF will NOT keep NPP valves open all the time. Even in the OFF setting, the NPP valves will still actuate by design in certain situations (low RPM, lugging, high gear highway, etc.). More pronounced in M7 below 1700RPM. M7 owners call this the "1700RPM hitch".
8. V4 operation will close the AFM valves and make the exhaust quiet even with NPP valves forced open (fuse 41/42 pulled). This is the biggest reason A6/8 owners may feel the NPP exhaust is 'too quiet' off throttle since it can spend so much time in V4 mode.
9. In M7 cars, pulling NPP fuse fixes ONLY the 1700RPM hitch that some (like me) find annoying and prevents NPP valves from closing at highway cruise even with ESM OFF.
10. NPP valves open all the time and V8 operation will result in hearing/feeling more low frequency content at low RPM all the time (highway especially). Some may like this, some may find this 'drone' objectionable.
11. Once NPP fuse is pulled, ESM obviously no longer has any effect, so you give up push button 'stealth mode'.
12. In automatics, pulling NPP fuse has less noticeable effect due to nearly constant V4 operation in low RPM/low load conditions. It gets quiet when AFM valves close...and therefore it's quiet even with NPP fuse pulled or ESM OFF. The 1700 RPM hitch is far less likely to occur in automatics, and in fact I'm not sure anyone has documented that it occurs at all in automatics.
13. Disabling V4 in automatics outside paddle/sport shift requires a tune or Range Technology OBDII plug (http://www.rangetechnology.com/).

 

By the way. If you just want it loud go into vehicle settings and adjust the exhaust to track there. That decouples the exhaust from the driving mode selector. Then you can put the car in tour mode for suspension and still have the more aggressive exhaust note.

 

This is what I do and it "remembers" the settings when I turn the car off. Tour for suspension (based on the console selector and what is shown on the display), Sport for steering (set in drving mode settings), and Track for exhaust. This gives me a comfortable ride around town which I can instantly tighten with the ****, nice sport steering, and obnoxious exhaust note. Perfect.

 

Will still go quiet if given the chance..ie 4v.

 

Ah. Mine is an m7. It only 4 cyls in Eco mode. (I think?)

 

correct

 

Thanks guys I think all is good now.