[db2022cs]

So, I have an SS with NPP. I have headers, and Corsa extreme exhaust. I have recently started having issues where when I put the car in stealth mode before turning off car but the startup is still open exhaust for like .5 seconds then closes for stealth. I do have a bit of valve rattle from the exhaust you can hear when valves are closed. I think it's time to replace them or have them looked at. Has anyone had this issue before? My car is loud as heck and that .5 seconds it's loud is something I hope I can fix. It's a nice feature to count on when early morning or in a public place where I don't want to startle people.

[arpad_m]

I never tried to leave the exhaust in stealth mode and don't think the car remain in this mode when it wakes up.

My suggestion is that you put the car into accessory or service mode by not using the pedals when you press the start button, change the exhaust to stealth, and then start the car normally.

This is the best you'll get, and if I remember correctly, even in stealth mode there is a very short bark when the ECM starts the engine. The only way to completely eliminate that is a tune that turns off fast catalytic converter warm-up.

[db2022cs]

Well, I have been doing it for the past 3 years nearly. It has only recently started doing this where it doesn't start fully silent. Only really happens if car sits overnight.
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[Gunkk]

That's normal.

The car will temporarily revert to "normal" during startup unless you do the following:

1) Turn the car KEY-ON-ENGINE-OFF (hit the start button twice with foot OFF the brake).
2) After the infotainment boots up, navigate to the manual mode settings page and set the exhaust to STEALTH manually. You will hear the valves close.
3) Start the car. It will start in Stealth and remain there.

[db2022cs]

Originally Posted by Gunkk

That's normal.

The car will temporarily revert to "normal" during startup unless you do the following:

1) Turn the car KEY-ON-ENGINE-OFF (hit the start button twice with foot OFF the brake).
2) After the infotainment boots up, navigate to the manual mode settings page and set the exhaust to STEALTH manually. You will hear the valves close.
3) Start the car. It will start in Stealth and remain there.

I turn the car off in stealth mode. For 3 years, it has worked where the car starts in stealth mode and the exhaust is quiet the entire time. I've done it hundreds of times in the past. This issue has only recently came up. I'm wondering if the valve actuators are needing to be replaced or if anyone has had issues with it doing this and have been able to fix it.

[KingLT1]

Yeah, mine started doing that when the valves developed issues. I had to put the car in service mode(hold start button with foot off brake for 5 seconds), toggle track mode then stealth and they would fully close on startup. From what I could tell the valve shafts develop play and sometimes they hang up and don't fully close...hence why you are experiencing a rattle now. I went through 3 different sets of Corsa Npp mufflers (replaced under warranty) before I gave up and just went to Corsa Sport Non NPP. I also had Flowmaster Npp and it was the same deal. I would find a low mileage ZL1 muffler if you must retain NPP.