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BeckyD @ James Martin Chevy


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Old 09-06-2020, 04:01 PM   #1
ThePeoplesCamaro
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NPP Exhaust Question....

Alrighty. First thread of many coming I’m sure as I start this build.

So I love the NPP feature. Being able to have a mild exhaust for apartment leaving is nice. But. About to be running Longtubes catless... still quiets down a great deal. But the fact that the car starts with those valves open for the first few seconds of the start sequences (upwards of 5-7 secs on a cold start). Still really pisses people off. Especially since I work crazy hours and start the car often at 2-3am. Is there a way to override this start function of the NPP valves. I saw a thread where someone messed around in the BCM to get it to default to auto rev on when the car starts. Is the answer in the BCM?
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Old 09-06-2020, 04:18 PM   #2
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Go into the vehicle settings and the exhaust setting and set to stealth before start up. This will close the valves.



You can either try to remember to put it in stealth before parking the car or if you forget, before starting the car press and hold the start/stop button for about 6 seconds, but don't press the brake pedal. This will power everything up and will be able to put it in stealth mode and then press the brake pedal and the start button again to start the engine.
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Old 09-06-2020, 04:28 PM   #3
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I will double check before saying officially this doesn’t work. But I start in touring mode... it’s obnoxiously loud for a few seconds. Then the valves close
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Old 09-06-2020, 04:40 PM   #4
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Originally Posted by ThePeoplesCamaro View Post
I will double check before saying officially this doesn’t work. But I start in touring mode... it’s obnoxiously loud for a few seconds. Then the valves close

Touring yes the valves will open for start. Stealth mode keeps the valves closed for engine start.



See this video at 1:30.



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Old 09-06-2020, 05:35 PM   #5
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I see said the blind man. Thank you sir. It’s to bad stealth mode can’t be one of the mode selects so if you only want quiet for the couple minutes when you start it can’t go back to loud easily
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Old 09-06-2020, 07:57 PM   #6
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There is probably a way to splice in a switched power wire into the NPP circuit to send power to the valves before you start. Then turn it back off to regain NPP function. Be sure to use diodes to prevent feedback.


Instead of completely pulling the F51 fuse, I ran the circuit through a switch (with a fuse) and back to the fuse port so I can set when I want the valves controlled by the car, such as around the LEOs.
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Old 09-06-2020, 08:21 PM   #7
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Pretty sure snow/ice mode is stealth sound.
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Old 09-06-2020, 08:40 PM   #8
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Quote:
Originally Posted by GroundhogSS View Post
There is probably a way to splice in a switched power wire into the NPP circuit to send power to the valves before you start. Then turn it back off to regain NPP function. Be sure to use diodes to prevent feedback.


Instead of completely pulling the F51 fuse, I ran the circuit through a switch (with a fuse) and back to the fuse port so I can set when I want the valves controlled by the car, such as around the LEOs.


Yes I’m interested in this if we can figure it out. I even have a spot for the switch. My cigarette lighter is disconnected completely as the wires are the power source for my gauges. A switch would go there much better
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Old 09-07-2020, 05:38 AM   #9
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Old 09-07-2020, 08:45 AM   #10
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Pretty sure snow/ice mode is stealth sound.
Snow/ice will have the exhaust valves behave like tour where it will open for start and then close.
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Old 09-07-2020, 09:28 AM   #11
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Quote:
Originally Posted by ChevyRules View Post
Go into the vehicle settings and the exhaust setting and set to stealth before start up. This will close the valves.



You can either try to remember to put it in stealth before parking the car or if you forget, before starting the car press and hold the start/stop button for about 6 seconds, but don't press the brake pedal. This will power everything up and will be able to put it in stealth mode and then press the brake pedal and the start button again to start the engine.
Whether you leave it in Stealth or not, it will bark on startup because the valves are always open when the car is off. Upon starting, the car will read the settings and close the valves if they are set for that.

If you want to silence the car as much as is absolutely possible, you need to press and hold the start button (don't put your foot on the brake/clutch) until it "powers on". Wait about 6 or 7 seconds, THEN start the car. This puts the car into Service Mode and should close the valves prior to the actual startup.
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Old 09-07-2020, 09:37 AM   #12
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Originally Posted by ember1205 View Post
Whether you leave it in Stealth or not, it will bark on startup because the valves are always open when the car is off. Upon starting, the car will read the settings and close the valves if they are set for that.

If you want to silence the car as much as is absolutely possible, you need to press and hold the start button (don't put your foot on the brake/clutch) until it "powers on". Wait about 6 or 7 seconds, THEN start the car. This puts the car into Service Mode and should close the valves prior to the actual startup.
You are incorrect. If you put the exhaust in stealth before shutting it off, it remains in stealth the next start up and the valves do not open. I do this every day so I can start my car in the garage without waking up my 8mon old.

I keep the mode in sport, put the exhaust in stealth before turning it off, and when I start up the next morning at 5a, it keeps the valves closed and is quiet enough not to wake anyone.
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Old 09-07-2020, 10:03 AM   #13
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Agree, shut off in stealth it will startup in stealth. Also agree that you need to hold for more than 5 seconds to allow everything to boot up if it wasn't in stealth prior. I use this a lot due to how loud my car is if it is very early or late to not wake up the neighborhood.
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Old 09-07-2020, 10:06 AM   #14
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Put it in snow/ice mode before shutting down and it'll be in stealth for startup. If you get longtubes you can give up on not waking the neighbors though. Cold start is insane with lt's no matter what you do.
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