NPP Interior Drone
Thread Starter
1st Gear
Joined: Jan 2009
Posts: 1
Likes: 0
NPP Interior Drone
All,
New to the forum. I own a 2008 C6 with the NPP option. All is well with the system until the engine warms up. At that point the drone inside the car becomes annoying. The change is sudden. All at once the interior noise level increases. At 65 MPH when you hit a grade the noise becomes a bit much. Not quite sure what it sounds like outside the car, but after an hour or two of this, it take the pleasure out of the drive. I have taken it to the dealer and all indications are that this is, what it is.
Question: Is this the way the system works? Can it be tuned to eliminate the drone. Is there a problem with the system.
Looking for answers before I get radical and install a CORSA Sport system.
Appreciate any thoughts you may have.
New to the forum. I own a 2008 C6 with the NPP option. All is well with the system until the engine warms up. At that point the drone inside the car becomes annoying. The change is sudden. All at once the interior noise level increases. At 65 MPH when you hit a grade the noise becomes a bit much. Not quite sure what it sounds like outside the car, but after an hour or two of this, it take the pleasure out of the drive. I have taken it to the dealer and all indications are that this is, what it is.
Question: Is this the way the system works? Can it be tuned to eliminate the drone. Is there a problem with the system.
Looking for answers before I get radical and install a CORSA Sport system.
Appreciate any thoughts you may have.
Race Director
Joined: Jun 2005
Posts: 10,909
Likes: 2,701
From: Phila Suburbs 2023 C8 & 2013 650ix
A properly functioning NPP system never drones. Sounds like your butterflies are stuck in the open position and not staying closed below 3500 rpm like they are designed.
Based on what you are saying if you start the car cold and look at the tailpipe the butterflies will be closed and as the engine heats up they open. If that's true, there is something wrong with the system controlling them.
Based on what you are saying if you start the car cold and look at the tailpipe the butterflies will be closed and as the engine heats up they open. If that's true, there is something wrong with the system controlling them.
Burning Brakes
Joined: Mar 2008
Posts: 815
Likes: 1
From: Mesa "highlands" AZ
Just a quick thought.......
You shouldn't have much of a drone if the NPP system is operating correctly AND you are not "putting your foot into it" to climb the hills.
If you do not have the aftermarket control system (which allows YOU to choose open or closed), then you probably have something wrong.
With the car idling, view the exhaust from several feet away. You should be able to see the vacumn controled block-off plate inside the exhaust tips. If not.....MAYBE a blown fuse.
You shouldn't have much of a drone if the NPP system is operating correctly AND you are not "putting your foot into it" to climb the hills.
If you do not have the aftermarket control system (which allows YOU to choose open or closed), then you probably have something wrong.
With the car idling, view the exhaust from several feet away. You should be able to see the vacumn controled block-off plate inside the exhaust tips. If not.....MAYBE a blown fuse.
Team Owner
Joined: Nov 2007
Posts: 45,273
Likes: 8,545
From: Rochester, NY
A properly functioning NPP system never drones. Sounds like your butterflies are stuck in the open position and not staying closed below 3500 rpm like they are designed.
Based on what you are saying if you start the car cold and look at the tailpipe the butterflies will be closed and as the engine heats up they open. If that's true, there is something wrong with the system controlling them.
Based on what you are saying if you start the car cold and look at the tailpipe the butterflies will be closed and as the engine heats up they open. If that's true, there is something wrong with the system controlling them.
Racer
Joined: Jul 2008
Posts: 461
Likes: 0
From: Milford MA
Agreed, when I have the valves closed (M2W) it is quiet and drone free on the highway. Although if I open it in 6th gear on the highway and load up the motor it drones like hell. At all other points with the valves open it is much louder but does not necessarily drone much.
Last edited by 95blklsc; Jan 29, 2009 at 02:55 PM.
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Safety Car
Joined: Jun 2004
Posts: 3,563
Likes: 2
From: Dallas Tx
Sounds like something is not right. Exhaust valves shouldn't be open until x rpm, x throttle .... should be closed and quiet during normal highway cruising. Have it rechecked. Maybe they misunderstood the complaint.
Is this an auto or manual trans. The other thing that happens once warmed up is the torque converter locks. If there is a contact issue somewhere when the TCC locks this can really create a moan. Sometimes need to make sure things like the exhaust, motor mounts... aren't making any ground out contact. Sometimes up on a lift, look all around the rear diff for any witness marks of anything making contact that shouldnt.
After verifying that the NPP is working properly, I'd look at any clearance issues. Often what techs will do is loosen the exhaust and motor mounts. Rock everything at bit to settle into a better position, and then retighten.
My guess would be an exhaust ground out somewhere near the rear diff.
Is this an auto or manual trans. The other thing that happens once warmed up is the torque converter locks. If there is a contact issue somewhere when the TCC locks this can really create a moan. Sometimes need to make sure things like the exhaust, motor mounts... aren't making any ground out contact. Sometimes up on a lift, look all around the rear diff for any witness marks of anything making contact that shouldnt.
After verifying that the NPP is working properly, I'd look at any clearance issues. Often what techs will do is loosen the exhaust and motor mounts. Rock everything at bit to settle into a better position, and then retighten.
My guess would be an exhaust ground out somewhere near the rear diff.
Last edited by Michrider; Jan 29, 2009 at 03:04 PM.
Pro
Joined: Apr 2005
Posts: 702
Likes: 82
From: Ronkonkoma NY
St. Jude Donor '08-'09
All,
New to the forum. I own a 2008 C6 with the NPP option. All is well with the system until the engine warms up. At that point the drone inside the car becomes annoying. The change is sudden. All at once the interior noise level increases. At 65 MPH when you hit a grade the noise becomes a bit much. Not quite sure what it sounds like outside the car, but after an hour or two of this, it take the pleasure out of the drive. I have taken it to the dealer and all indications are that this is, what it is.
Question: Is this the way the system works? Can it be tuned to eliminate the drone. Is there a problem with the system.
Looking for answers before I get radical and install a CORSA Sport system.
Appreciate any thoughts you may have.
New to the forum. I own a 2008 C6 with the NPP option. All is well with the system until the engine warms up. At that point the drone inside the car becomes annoying. The change is sudden. All at once the interior noise level increases. At 65 MPH when you hit a grade the noise becomes a bit much. Not quite sure what it sounds like outside the car, but after an hour or two of this, it take the pleasure out of the drive. I have taken it to the dealer and all indications are that this is, what it is.
Question: Is this the way the system works? Can it be tuned to eliminate the drone. Is there a problem with the system.
Looking for answers before I get radical and install a CORSA Sport system.
Appreciate any thoughts you may have.
Consider adding M2W to compliment your NPP system. It can be purchased very reasonably from Pipedreams one of the most reputable venders on the forum and will only take about 10-15 minutes to install (Very simple installation) In the mild mode there is absolutely no drone at any speed.. lastly it will be a lot cheaper than changing over to a corsa system but give you the flexibility to run the NPP mufflers open or closed when you want. good luck with your choice
Melting Slicks
Joined: Oct 2003
Posts: 2,655
Likes: 5
From: Brea CA
Well
I have the NPP on mine.. with the Mild to Wild... only Drome I get is "IF" it is in the Wild mode... and I am in the 1500-1700 RPM Range.. If I am there a lot, I just push the Mild button... and it is all quiet. Mine is not RPM activated, it is a retro-fit. 
Drifting
Joined: Sep 2007
Posts: 1,331
Likes: 148
From: 1000 Islands Ontario
I think RnLi is right. Sounds like a blown fuse. Lift the carpet up at the top of the passenger foot well. There is a fuse labelled EXH MDL (Exhaust Module). I think it is 10 amps.
If this fuse is blown, the muffler butterflies will be open all the time.
As has been said here, start the car and have a peek at the business end of the tailpipes. If the butterflies are open at idle, the NPP circuitry has a problem. If they are closed, then you must have some kind of resonance/vibration going on.
Hope this helps.
M....
If this fuse is blown, the muffler butterflies will be open all the time.
As has been said here, start the car and have a peek at the business end of the tailpipes. If the butterflies are open at idle, the NPP circuitry has a problem. If they are closed, then you must have some kind of resonance/vibration going on.
Hope this helps.
M....
Safety Car
Joined: Feb 2007
Posts: 4,939
Likes: 448
From: CHOCOWINITY NC
As others have pointed out, this is not normal. Something is definitely amiss....either the fuse or a possible leak/problem in the vacuum system.
Valves should be closed except under the following condidtions:
Valves should be closed except under the following condidtions:
Drifting
Joined: Oct 2008
Posts: 1,354
Likes: 1
From: Inland Empire CA
St. Jude Donor '10
Oh, its the dreaded NPP drone. You must remove the NPP and install your aftermarket exhaust right away.
Then ship your old exhaust to me, in the box you new system came in, to prevent damage. PM me for my address.
Then ship your old exhaust to me, in the box you new system came in, to prevent damage. PM me for my address.
