[Paintslinger16]

Originally Posted by s346k

i would swap neighbors before i swapped exhaust

I am stealing this for a signature

[ember1205]

Originally Posted by bjbonentte

Here is what I do. No matter what mode you park the car in you can do this and it works.

Get in car, hold down start button only, do not push brake and clutch. You will have to hold down the button for 5-6 seconds and the car will go into accessory mode. Everything will be alive like if the car was running. Now put the car into snow/winter mode using the selector. You will hear the valves close. Now brake, clutch and push the start button again. Car will start in stealth mode without having to actually go into menu and select stealth. Once you leave the neighborhood you click it back into sport or track and good to go.

Holding the Start button for 5-6 seconds, with your foot OFF of the brake, will put the car into Service Mode (not Accessory Mode). Service Mode powers -everything- on as if the car were started, and you get full access to the various Infotainment menus and such. This mode is intended specifically for when you need to have the car completely "on" but without the engine running and is commonly used by service techs for pulling codes, clearing codes, re-programming, etc.

As far as valves being opened or closed during startup, it's important to understand that the valves will always -OPEN- when you turn the car off. There is a spring-loaded lever that forces the valves open and applying the correct electrical signals to the actuators (and maintaining that signaling, meaning the car is "ON") is the only way to get them to close and stay closed.

My understanding of Stealth Mode is that it causes the valves to close "right away" upon startup instead of the common 6-10 second delay for other modes. As mentioned, this is done specifically to allow the computer to dump extra fuel into the motor and get the cats warmed up as quickly as possible. Stealth Mode will override that typical behavior and close the valves very quickly while changing the rev level and fuel ratio so as to still get the cars warmed up quickly. Stealth Mode is quietER, but by no means truly quiet overall, on startup.

[turbo2ltr]

Thanks everyone! Wish GM had take just one extra step and allowed mode-level customization of the exhaust/steering/suspension instead of global overrides.

Having to do a song and dance before each startup is too much.

Stealth mode it is. Every little bit helps. I'm probably overreacting. Both neighbors are car guys. But I'm a quiet kinda guy when it comes to respecting my quiet neighborhood. I like the quiet, though not necessarily in my cars. When I had my 80 camaro with Thrush Sonic Turbos on it and it sounded soooo good, especially at 6800rpm. But after a night if "cruising", I'd turn the car off two blocks away from my house and coast into my parking spot. lol.

[ember1205]

Originally Posted by turbo2ltr

Thanks everyone! Wish GM had take just one extra step and allowed mode-level customization of the exhaust/steering/suspension instead of global overrides.

Having to do a song and dance before each startup is too much.

Stealth mode it is. Every little bit helps. I'm probably overreacting. Both neighbors are car guys. But I'm a quiet kinda guy when it comes to respecting my quiet neighborhood. I like the quiet, though not necessarily in my cars. When I had my 80 camaro with Thrush Sonic Turbos on it and it sounded soooo good, especially at 6800rpm. But after a night if "cruising", I'd turn the car off two blocks away from my house and coast into my parking spot. lol.

I get it... I'm in a similar situation as my car does not have NPP but I am looking to add an exhaust to it that uses the controllers.

There's information available on how to build your own controller circuit, including an override that will work in NPP-equipped cars to force the valves closed with a hard switch, or there are a couple of aftermarket options out there as well. Additionally, HPTuners is now apparently able to add the exhaust control into cars that didn't come from the factory with it, but that requires a tune and it's another warranty-voiding thing that I want to avoid.

[UnknownJinX]

The newer Mustangs do have that "Good Neighbour Mode" or whatever and I can see it being handy if you have a very particular neighbour.

At the same time, meh, I'd just leave mine on Touring/Sport until someone complains to me.

[Rhobz]

My understanding is that every time you shut the car off, the valves open, no matter what mode you are in so that they do not freeze closed. If the NPP system ever fails, you would want it to fail open, not closed, which is why they default to open when the car is off.

[ember1205]

Originally Posted by Rhobz

My understanding is that every time you shut the car off, the valves open, no matter what mode you are in so that they do not freeze closed. If the NPP system ever fails, you would want it to fail open, not closed, which is why they default to open when the car is off.

Yes, this is accurate.

As mentioned earlier, shutting the car off kills the control power to the valve that holds it in a closed position. The spring-loaded lever on the valve itself is then able to swing the butterfly valve back open.

When you start the car again, the car is able to supply control power to cause the valve to rotate closed and hold that position.

[cdrptrks]

Originally Posted by GroundhogSS

From what I have heard before, you have to set it every time you start the car. It doesn't remember when you power it off.

Go into accessory mode by pushing the start button without your foot on the break. Then set the mode to stealth and start the car.
Mine is a 2017 so it may be different in later models.

Mine remembers the previously selected mode when you power it off. I normally switch to stealth mode when entering my neighborhood so my neighbors hear the next startup less.

The accessory/service mode trick is handy if I forget or am unsure of what mode I left it in previously.

I wonder if there is any noise level difference in stealth exhaust mode between starting from accessory/service mode vs. normal engine start procedure. I haven't noticed any difference myself.

[bjbonentte]

Originally Posted by ember1205

Holding the Start button for 5-6 seconds, with your foot OFF of the brake, will put the car into Service Mode (not Accessory Mode). Service Mode powers -everything- on as if the car were started, and you get full access to the various Infotainment menus and such. This mode is intended specifically for when you need to have the car completely "on" but without the engine running and is commonly used by service techs for pulling codes, clearing codes, re-programming, etc.

As far as valves being opened or closed during startup, it's important to understand that the valves will always -OPEN- when you turn the car off. There is a spring-loaded lever that forces the valves open and applying the correct electrical signals to the actuators (and maintaining that signaling, meaning the car is "ON") is the only way to get them to close and stay closed.

My understanding of Stealth Mode is that it causes the valves to close "right away" upon startup instead of the common 6-10 second delay for other modes. As mentioned, this is done specifically to allow the computer to dump extra fuel into the motor and get the cats warmed up as quickly as possible. Stealth Mode will override that typical behavior and close the valves very quickly while changing the rev level and fuel ratio so as to still get the cars warmed up quickly. Stealth Mode is quietER, but by no means truly quiet overall, on startup.

That is great and all but This is what I do when I want to close the valves on startup. works, easy, don't have to fumble through screen before turning the car off the night before. Try it.

[ember1205]

Originally Posted by bjbonentte

That is great and all but This is what I do when I want to close the valves on startup. works, easy, don't have to fumble through screen before turning the car off the night before. Try it.

Um... what? lol

[GroundhogSS]

Originally Posted by cdrptrks

Mine remembers the previously selected mode when you power it off. I normally switch to stealth mode when entering my neighborhood so my neighbors hear the next startup less.

The accessory/service mode trick is handy if I forget or am unsure of what mode I left it in previously.

I wonder if there is any noise level difference in stealth exhaust mode between starting from accessory/service mode vs. normal engine start procedure. I haven't noticed any difference myself.

It stays in the mode I set it in, usually Sport, here also. The bottom line is that when the car is off, there is no power to the valves and the spring will flip them open. You will always get that loud crack from the mufflers on startup because the valves are open. It takes a second or two before the system will close them. The only way I know of to have them close on startup is the method of going into stealth mode through the screen while in accessory mode.

[SSDan]

And regardless of which mode is selected there always will be the high rpm bark at start up. In order to get a 6.2 L engine to pass the EPA sniff tests the GM engineers had to get the cats to operating temp as quickly as possible. They accomplish this with a high rpm start and the injectors double pulse to create a rich fuel exhaust condition that in turn allows the cats to reach operating temp quickly. So while stealth mode will help at startup to dampen the sound the big bark is still going to happen.

OP - some people who garage park back the car in so that the startup bark is muffled a little more. Of course if you do this you run the risk of the wrath of the wife/significant other as the pictures rattle off the wall!

I'm lucky - all my neighbors like the sound of big American muscle. So my start ups make them smile.

[2SSRedline]

My neighbor has a Harley so it's offsetting penalties.

[Booher]

You guys are making it waaaaaay to complicated! Like i said drive in any mode, when you get home or pull up into your driveway change it to stealth before you shut it off and it will be in stealth when you start it. All the guys saying different, why don't you try it first before you say different. What would the car care if the valves closed? Its just going through a muffler like any other car in the world always has, not a big deal, lol. It will still "bark", but that's literally for 1 second, and any mode will do that.