Stealth mode turning on by itself...dealership clueless

[12years]

Very weird.....has anyone else experienced this?
Bought my 2019 GS M7 hardtop July 2021 with 5300km. No exhaust issues at the beginning.

Now, for the past 1-2 months, it sounds as if stealth mode activates by itself while I'm driving as per usual with the exhaust in track mode and the drive mode in sport. It happens ONLY in 3rd gear when I let off the throttle....if I give it soft/hard throttle its silent until I hit 2,700 RPM and then sounds like track mode again/valves open again. The track mode sound also comes back in 3rd gear if let the RPM drop to 1600 without touching the throttle...if i give it throttle at this point sound is in track mode again....then if I let off throttle again it sounds like stealth mode again until either falling to 1600 or revving to 2700rpm. When the silence is there it will continue if I downshift to 2nd, but not if I upshift to 4th.

Have been to the dealership (with at least one Corvette tech onsite at all times) once already for this issue and they had no idea what to do about it. They were apparently later told by GM that this is a "normal occurrence" because of eco mode/location where the car was sold, and that they have heard one case of this before in Canada and another in the US.....what??? That makes no sense. There problem wasn't there when I first got the car, only happens in 3rd gear, and I am NEVER in eco mode....

Can anyone shed any light on this? They are proposing strapping a Go-Pro camera to the exhaust in order to visualize the valves while driving. I'm dropping the car off again tomorrow.

 

[Rruuff Day]

Weird one Vaughan. Being an M7, it should never drop to eco mode unless it's dialed up. I have my M7 in track mode exhaust as well and drive in sport mode continuously and have never had this happen. Almost sounds like it's sensing Tour mode maybe. Keep us posted on what you find out.

 

[WPGZ06]

Being a M7, that is very odd, definitely a program issue it sounds like

 

[cdnrx1]

Very weird.....has anyone else experienced this?
Bought my 2019 GS M7 hardtop July 2021 with 5300km. No exhaust issues at the beginning.

Now, for the past 1-2 months, it sounds as if stealth mode activates by itself while I'm driving as per usual with the exhaust in track mode and the drive mode in sport. It happens ONLY in 3rd gear when I let off the throttle....if I give it soft/hard throttle its silent until I hit 2,700 RPM and then sounds like track mode again/valves open again. The track mode sound also comes back in 3rd gear if let the RPM drop to 1600 without touching the throttle...if i give it throttle at this point sound is in track mode again....then if I let off throttle again it sounds like stealth mode again until either falling to 1600 or revving to 2700rpm. When the silence is there it will continue if I downshift to 2nd, but not if I upshift to 4th.

Have been to the dealership (with at least one Corvette tech onsite at all times) once already for this issue and they had no idea what to do about it. They were apparently later told by GM that this is a "normal occurrence" because of eco mode/location where the car was sold, and that they have heard one case of this before in Canada and another in the US.....what??? That makes no sense. There problem wasn't there when I first got the car, only happens in 3rd gear, and I am NEVER in eco mode....

Can anyone shed any light on this? They are proposing strapping a Go-Pro camera to the exhaust in order to visualize the valves while driving. I'm dropping the car off again tomorrow.

Well, this is just another example of what I've been saying all along. Dealers and their "Corvette techs", are, in many instances, incompetent.

GM is correct in stating that this is normal behavior for the NPP exhaust. Although you can select the specific exhaust mode, in your case track, the system is designed to default to stealth mode under certain conditions. I'm not sure of the specific algorithm but it has to do with drive mode selection, road speed, the gear selected and engine RPM. It usually happens under deceleration/light load, around 60 kph and less than 3000 RPM. These are approximates. Apparently, it has something to do with noise regulations in some states where decibel levels must be under a certain value at or below 35 mph.

I have a '19 GS, A8 and it performs this way during the normal course of operation. The only way to prevent it is to pull the NPP fuse thus leaving the valves fully open. Once again, it is normal behavior don't worry about it and take what the dealer says with a pound of salt.

Hope this helps.

Best regards
Ross

 

[AxeZ06]

My '17 Z06 M7 did the same thing. Usually at cruising speed.
In 6th or 7th gear, it often went stealth on it's own. The only way to get the "loud" to kick back in, was to up the speed to 127kph.
So I sold it.

 

[Darren]

I don’t believe this is stealth mode , check your dash when this happens on the screen with mileage per gallon trip. I think it’s going in 4 cylinder mode. I keep mine on track mode under engine management screen , drive in manual (obviously a auto) and never have this issue. If I go in Drive mode the car will de activate cylinders for gas savings.

 

[Darren]

Weird one Vaughan. Being an M7, it should never drop to eco mode unless it's dialed up. I have my M7 in track mode exhaust as well and drive in sport mode continuously and have never had this happen. Almost sounds like it's sensing Tour mode maybe. Keep us posted on what you find out.

Track mode on the dial, is different than in the settings in computer for engine management.

 

[Kanuck]

Perhaps you could pull fuse #42 (verify # in Owners Manual ) to keep the NPP Exhaust in Track mode all the time and see how that works.
I always have mine set in Track Mode but don't experience what you described. M7 does not go in to Eco V4 Mode unless you select it.

 

[Rruuff Day]

Track mode on the dial, is different than in the settings in computer for engine management.

Guess I wasn't clear... I have mine set Track in engine management options to keep my exhaust valves open. Don't use Track on the dial unless I want the additional performance options, which is seldom. Sport mode is my daily "dial" mode... Tour and Eco may be available on my dial but may as well not be there as they are never used.

 

[Darren]

Okay, set your dash to trip 1 and when your exhaust goes quiet see if you see the V4 on. I know you said you have a manual, but this may be the cause. Maybe Rouff, can tell you all his setting as he has manual.

 

[Cariboocreek]

Guess I wasn't clear... I have mine set Track in engine management options to keep my exhaust valves open. Don't use Track on the dial unless I want the additional performance options, which is seldom. Sport mode is my daily "dial" mode... Tour and Eco may be available on my dial but may as well not be there as they are never used.

Mostly the same here but I do use Tour in towns as potholes have been known to be "rough" on stock C7 GS/ZO6 rims.

 

[Canuck204]

Perhaps you could pull fuse #42 (verify # in Owners Manual ) to keep the NPP Exhaust in Track mode all the time and see how that works.
I always have mine set in Track Mode but don't experience what you described. M7 does not go in to Eco V4 Mode unless you select it.

Id try that aslo. M2W also a nice option.

 

[Rruuff Day]

Okay, set your dash to trip 1 and when your exhaust goes quiet see if you see the V4 on. I know you said you have a manual, but this may be the cause. Maybe Rouff, can tell you all his setting as he has manual.

Nothing earth shattering for setting track mode exhaust. On the infotainment screen, click Settings. Click Driving Mode, then Engine Sound management. Scroll down and push Track. That's all. Mine remains in Track exhaust sound with the valves open no matter where I turn the mode dial to or where the rpms are. If you want to adjust the steering, just back up one screen, push Steering, and you can set you steering stiffness the same way. Like I said, my C7 is an M7. Not sure what the final results will be on an A8.

 

[Darren]

Nothing earth shattering for setting track mode exhaust. On the infotainment screen, click Settings. Click Driving Mode, then Engine Sound management. Scroll down and push Track. That's all. Mine remains in Track exhaust sound with the valves open no matter where I turn the mode dial to or where the rpms are. If you want to adjust the steering, just back up one screen, push Steering, and you can set you steering stiffness the same way. Like I said, my C7 is an M7. Not sure what the final results will be on an A8.

That’s what I do also, with an auto.
Only diff is if I am NOT in manual shift mode and just cruising down the road it goes to eco v4.
needless to say I drive with paddle shifting manual all the time.
I just added long tube headers, matching diameter cross over pipes, cat delete, Borla mufflers, (attac) and remapped computer. Simply put WOW, great sound noticeable power and torque increase.

 

[Rruuff Day]

That’s what I do also, with an auto.
Only diff is if I am NOT in manual shift mode and just cruising down the road it goes to eco v4.
needless to say I drive with paddle shifting manual all the time.
I just added long tube headers, matching diameter cross over pipes, cat delete, Borla mufflers, (attac) and remapped computer. Simply put WOW, great sound noticeable power and torque increase.

They should have been able to delete Eco when they did your tune. I assume with those mods that a tune was done as well. If not, there are AFM devices available to get rid of eco even when you auto shift if I'm not mistaken.

 

[Darren]

They should have been able to delete Eco when they did your tune. I assume with those mods that a tune was done as well. If not, there are AFM devices available to get rid of eco even when you auto shift if I'm not mistaken.

Yes, tuned. Decided to leave eco mode available, if we are on a cross province or country trip it does come in handy. Not to mention long highway drives a little gas saving is good. As today premium is 1.50 to 1.73 per litre.

 

[Rruuff Day]

Yes, tuned. Decided to leave eco mode available, if we are on a cross province or country trip it does come in handy. Not to mention long highway drives a little gas saving is good. As today premium is 1.50 to 1.73 per litre.

Tried Eco on a trip first year with the C7. Found such a minor difference in fuel mileage that I never used it again. That's what 7th gear is for...lol...