NPP Exhaust Question
Thread Starter
Burning Brakes
Joined: Jul 2009
Posts: 799
Likes: 14
From: Lakewood Ranch FL
NPP Exhaust Question
I have an '08 Coupe with the NPP. Took the fuse out for the louder sound. The car does sound louder. Question- The butterflys seem to be closed with car on or off. Is that correct? If not what can I do?? 
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
Stock NPP or Z06 exhaust has open baffles when the car is off. The baffles close as soon as the car builds vacuum (a few seconds after starting) and stay closed until the RPM/throttle position requirements are met.
Add an exhaust controller and you can set the baffles to open or close just about any way you want.
Add an exhaust controller and you can set the baffles to open or close just about any way you want.
Safety Car
Joined: Nov 2007
Posts: 4,436
Likes: 875
From: Bay Area CA
Stock NPP or Z06 exhaust has open baffles when the car is off. The baffles close as soon as the car builds vacuum (a few seconds after starting) and stay closed until the RPM/throttle position requirements are met.
Add an exhaust controller and you can set the baffles to open or close just about any way you want.
Add an exhaust controller and you can set the baffles to open or close just about any way you want.
That's how my 08 oem NPP exhuast works
Instructor
Joined: Jul 2007
Posts: 124
Likes: 0
From: Roseville Ca.
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Burning Brakes
Joined: Jul 2004
Posts: 858
Likes: 3
From: Livonia Michigan
I pulled the fuse on mine, and the car is definitely louder, but nothing like a wide open exhaust sound I thought it would be. I checked to see the baffles, and they are open, but not completely. I'd say about half or three quarters of the way. Hmmm, I will replace the fuse in it's place, start it up and let it run awhile, then pull it out again to see if the baffles change the opening any more than it did before. Just to satisfy my curiosity on whether they are wide open or not.
Advanced
Joined: Mar 2010
Posts: 75
Likes: 0
The Mild to Wild kit that I have not installed yet comes with a fuse/adapter which utilizes the seat warmer (option I do not have) slot. The baffles look wide open right now. I don't think that will make any difference in my case. Sounds great as is!
Race Director
Joined: Jun 2005
Posts: 10,910
Likes: 2,701
From: Phila Suburbs 2023 C8 & 2013 650ix
Installation from the factory should be full open with engine shutdown. With fuse pulled they should always be full open. I don't understand how both sides could be jammed shut due to a malfunction. One side maybe, not both. Are you sure it was a factory installation?
And how cant they be louder with the fused pulled it they stay closed? Your description is contradictory.
And how cant they be louder with the fused pulled it they stay closed? Your description is contradictory.
Safety Car
Joined: Mar 2009
Posts: 4,101
Likes: 719
From: Northeast MA & Mad Beach FL
I'd check the linkage above the exhaust tips that control the butterfly plates.
With the car shut off, fiddle with the linkage with your hand and see if they're stuck or something.
They don't move freely but they should move smoothly.
As mentioned, with the fused pulled, or, car shut off, the butterfles should be wide open
Thread Starter
Burning Brakes
Joined: Jul 2009
Posts: 799
Likes: 14
From: Lakewood Ranch FL
OK, checked the linkage and seemed that the vacumns were moving but not the butterflys. Played around and got one to open! 
The other one still not opening! Got a little aggressive and tried to force the butterfly to move. Got too aggresive and now the butterfly is spinning freely.
I guess I broke something. Tried to keep the butterfly open and hold in place by "jamming it". Don't believe this will permanently hold. Any ideas?
Can the butterfly be removed?
The other one still not opening! Got a little aggressive and tried to force the butterfly to move. Got too aggresive and now the butterfly is spinning freely. I guess I broke something. Tried to keep the butterfly open and hold in place by "jamming it". Don't believe this will permanently hold. Any ideas? Can the butterfly be removed?
Safety Car
Joined: Feb 2007
Posts: 4,942
Likes: 4
From: LINCOLN RI - 2010 GS Coupe - 2007 Coupe
OK, checked the linkage and seemed that the vacumns were moving but not the butterflys. Played around and got one to open! The other one still not opening! Got a little aggressive and tried to force the butterfly to move. Got too aggresive and now the butterfly is spinning freely. I guess I broke something. Tried to keep the butterfly open and hold in place by "jamming it". Don't believe this will permanently hold. Any ideas? Can the butterfly be removed?
The other one still not opening! Got a little aggressive and tried to force the butterfly to move. Got too aggresive and now the butterfly is spinning freely. I guess I broke something. Tried to keep the butterfly open and hold in place by "jamming it". Don't believe this will permanently hold. Any ideas? Can the butterfly be removed?Yeah, take it to a qualified mechanic which is what you should have done before you broke it.
Racer
Joined: Apr 2008
Posts: 347
Likes: 0
From: Chantilly VA
On stock the butterflys close when you shut the car off and open on start then close. They open when at throttle of 2500 or 3000rpm. I got mild to wild and they start open and stay open until you close them.
Drifting
Joined: Oct 2007
Posts: 1,565
Likes: 2
From: The Great Pacific Northwest...........I carry a gun cause a cops too heavy.
The above is correct. The engine has to be running to create the vacuum needed to close the valves, stomp on it, the vacuum goes away and the valves open.
