NPP Question
Thread Starter
Instructor
Joined: Apr 2016
Posts: 246
Likes: 77
NPP Question
It seems like the exhaust is wide open when starting the car, then changes to whatever mode you're in roughly after a minute or so. Is there anyway to start in 'stealth' or touring? I leave pretty early sometimes, just trying not to wake the neighbors..
Le Mans Master
Joined: Aug 2015
Posts: 6,884
Likes: 2,884
From: Toronto
I believe you are out of luck. There have been some other discussions on this. Some say the AFM valve and/or fuel mix is different at start up which impacts the sound. The NPP is not the cause of this (so I've read).
Burning Brakes
Joined: Dec 2015
Posts: 812
Likes: 192
Put it in stealth mode before turning it off the night before, it will start with the valves fully closed. That is as quiet as it can start.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.
Melting Slicks
Joined: Aug 2014
Posts: 2,746
Likes: 916
Do you park it in a garage? My old souped up G8 was super loud at cold start up due to the long tube headers/high flow cats I had installed. Anyway, once it fired, it would rather quickly quiet down. So I would start it with the garage door closed and immediately open the garage door after the initial rev. Before the folks start freaking out about CO poisoning risk, I'm only talking about a few seconds of run time with the door closed...
Last edited by lakemg; Jun 7, 2016 at 09:07 PM.
Burning Brakes
Joined: Mar 2014
Posts: 1,140
Likes: 406
From: Greater Cincinnati Area
9balls has it correct in post #4. I have the wireless control built to remotely "pull" fuse 42 when I want, and the car is very quiet when started in stealth mode...at 4 a.m., when I'm headed off to work.
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Burning Brakes
Joined: Aug 2014
Posts: 990
Likes: 207
From: Bay Area CA
Put it in stealth mode before turning it off the night before, it will start with the valves fully closed. That is as quiet as it can start.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.
Burning Brakes
Joined: Dec 2015
Posts: 812
Likes: 192
Melting Slicks
Joined: Apr 2002
Posts: 2,439
Likes: 590
From: Tellico Plains Tennessee
If you have doubts about whether the valves are open or closed just take a look. You can see the NPP valves easily by looking into the 2 outer pipes. My C7 is loud with the valves closed, very loud with the valves open.
Burning Brakes
Joined: Aug 2014
Posts: 990
Likes: 207
From: Bay Area CA
Thread Starter
Instructor
Joined: Apr 2016
Posts: 246
Likes: 77
Put it in stealth mode before turning it off the night before, it will start with the valves fully closed. That is as quiet as it can start.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.
It is a bit louder on startup due to the cold exhauset system, all cars with high flow mufflers are the same way, once they start to heat up, they quiet down.