Muffler Question
Thread Starter
Instructor
Joined: Jul 2000
Posts: 242
Likes: 33
From: MN
Muffler Question
I recently bought a 2010 GS with stock mufflers (non-NPP) and I'm starting to think about replacing them. I'm looking at all the usual Borla, Corsa, B&B, etc. but I've also seen a number of factory NPP mufflers for sale. I have no intention of fully installing the NPP system but can these mufflers be installed and just set (mechanically) to full open?
For those of you that run the NPP system full open regularly, how does the sound (quality and quantity) compare to some of the aftermarket systems? Does is become more Borla Touring or Atak or somewhere in between? Just curious...thanks!
For those of you that run the NPP system full open regularly, how does the sound (quality and quantity) compare to some of the aftermarket systems? Does is become more Borla Touring or Atak or somewhere in between? Just curious...thanks!
Melting Slicks
Joined: Oct 2004
Posts: 2,863
Likes: 150
From: Woodland CA
Yes you can have the NPP installed and just have it open. I have NPP with the Mild to Wild switch. I run 99.9% open. Pretty much a waste of money for me and I should have just pulled the fuse. Oh well.
I like the way it sounds. There are times where I feel I would want it louder but I don't want to swap it and then end up with drone.
I like the way it sounds. There are times where I feel I would want it louder but I don't want to swap it and then end up with drone.
Race Director
Joined: Mar 2010
Posts: 16,896
Likes: 5,359
From: T-Town WA
2016 C6 of Year Finalist
I think the default position is open, so if you installed the muffs without the vacuum lines they should remain open.
I've had mine open for three years...never close them.
I've had mine open for three years...never close them.
Thread Starter
Instructor
Joined: Jul 2000
Posts: 242
Likes: 33
From: MN
Yes you can have the NPP installed and just have it open. I have NPP with the Mild to Wild switch. I run 99.9% open. Pretty much a waste of money for me and I should have just pulled the fuse. Oh well.
I like the way it sounds. There are times where I feel I would want it louder but I don't want to swap it and then end up with drone.
I like the way it sounds. There are times where I feel I would want it louder but I don't want to swap it and then end up with drone.
Safety Car
Joined: Feb 2016
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From: SC
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Thread Starter
Instructor
Joined: Jul 2000
Posts: 242
Likes: 33
From: MN
Race Director
Joined: Mar 2010
Posts: 16,896
Likes: 5,359
From: T-Town WA
2016 C6 of Year Finalist
14-1500 on the throttle there is some drone. Either get off the throttle or out of that gear.
The factory mufflers are specifically designed to not only block but cancel drone frequencies. Opening the NPP sends the exhaust straight out the pipes. Borla and Corsa design cancels out some frequencies. as well as ensures that the sound energy is going out the tailpipes. Corsa's designs have an internal chamber that is of the correct length to cancel this frequency out using the laws of wave reflection.
The factory mufflers are specifically designed to not only block but cancel drone frequencies. Opening the NPP sends the exhaust straight out the pipes. Borla and Corsa design cancels out some frequencies. as well as ensures that the sound energy is going out the tailpipes. Corsa's designs have an internal chamber that is of the correct length to cancel this frequency out using the laws of wave reflection.
Safety Car
Joined: Nov 1999
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From: Green and Wet Western Oregon
2023 C7 of the Year Winner - Unmodified
2018 C6 of Year Winner
I also have a GS (convertible), but I put Corsa Sport on ours. Love the Corsa, but a lot more money than you want to spend.
Melting Slicks
Joined: Oct 2004
Posts: 2,863
Likes: 150
From: Woodland CA
Drone affects people differently. For me the open NPP on my M6 the drone is almost non-existent. While there is some there it is completely livable. However, if you tend to be more sensitive to drone then you should leave the stock mufflers on.
On my 2005 C6 I had Magnaflow exhaust + long tubes + mild cam and the drone was insane. Got so bad I put the stock mufflers back on.
On my 2005 C6 I had Magnaflow exhaust + long tubes + mild cam and the drone was insane. Got so bad I put the stock mufflers back on.
Race Director
Joined: Mar 2011
Posts: 13,262
Likes: 3,151
From: SW Florida
2021 C6 of the Year Finalist - Modified
2011 GS (A6)
The NPP mufflers are ok. Almost too quiet until you put your foot in it and the valves open up. Then the NPP sounds nice. As others have said ... Pull the NPP fuse and the valves will always remain open. With the stock exhaust manifolds, there is nothing wrong with the NPP system.
My problem with the NPP ...... I later installed a set of long-tube catted headers. After the headers install, the NPP mufflers became obnoxiously loud when the valves opened up. So loud at full throttle that I removed them and replaced them with a set of Borla 'Touring' mufflers.
The Borla 'Touring' mufflers are a little louder during idle and normal driving than the NPP system was when the NPP valves are closed (a good thing), but much quieter than the NPP system was when the NPP valves opened up (also a good thing).
Long-tube catted headers and the Borla 'Touring' mufflers ..... No drone at all on the highway, and for me ..... it's a Win-Win situation now
.
The NPP mufflers are ok. Almost too quiet until you put your foot in it and the valves open up. Then the NPP sounds nice. As others have said ... Pull the NPP fuse and the valves will always remain open. With the stock exhaust manifolds, there is nothing wrong with the NPP system.
My problem with the NPP ...... I later installed a set of long-tube catted headers. After the headers install, the NPP mufflers became obnoxiously loud when the valves opened up. So loud at full throttle that I removed them and replaced them with a set of Borla 'Touring' mufflers.
The Borla 'Touring' mufflers are a little louder during idle and normal driving than the NPP system was when the NPP valves are closed (a good thing), but much quieter than the NPP system was when the NPP valves opened up (also a good thing).
Long-tube catted headers and the Borla 'Touring' mufflers ..... No drone at all on the highway, and for me ..... it's a Win-Win situation now
.
Last edited by Turbo6TA; Nov 18, 2016 at 04:17 PM.
Burning Brakes
Joined: Dec 2015
Posts: 786
Likes: 155
From: Oak Island NC
As previously stated, the default position of the NPP butterfly valve is open. I just purchased NPPs for my non-NPP 2013 base coupe from a forum member [great transaction BTW]. Since I do not want to get involved with installing vacuum lines, wiring, etc. at this point the valves will remain open all the time. If the open position is too loud then I will clamp the valve in a partially open position.
The link below talks about clamping the NPP valves to be partially open. Posts #48 & #49 have pictures that might be helpful for this type of low tech approach.
https://www.corvetteforum.com/forums...ly-open-3.html
As a gentle reminder, axle back NPPs from a 2009+ base coupe or GS should be a direct bolt on to your 2010 GS. GLW your decision.
The link below talks about clamping the NPP valves to be partially open. Posts #48 & #49 have pictures that might be helpful for this type of low tech approach.
https://www.corvetteforum.com/forums...ly-open-3.html
As a gentle reminder, axle back NPPs from a 2009+ base coupe or GS should be a direct bolt on to your 2010 GS. GLW your decision.
Last edited by Yaupon; Nov 19, 2016 at 08:40 AM.
Drifting
Joined: Jul 2011
Posts: 1,825
Likes: 443
From: Boca Raton Florida
Originally Posted by Homer3D
Drone affects people differently. For me the open NPP on my M6 the drone is almost non-existent. While there is some there it is completely livable. However, if you tend to be more sensitive to drone then you should leave the stock mufflers on.
On my 2005 C6 I had Magnaflow exhaust + long tubes + mild cam and the drone was insane. Got so bad I put the stock mufflers back on.
On my 2005 C6 I had Magnaflow exhaust + long tubes + mild cam and the drone was insane. Got so bad I put the stock mufflers back on.
Race Director
Joined: Mar 2010
Posts: 16,896
Likes: 5,359
From: T-Town WA
2016 C6 of Year Finalist
I just made a 1600 mile trip in my GS with the NPP open. There was drone once or twice on the freeway when, at 1400 rpm, I got on the throttle fairly heavy. To me that is almost lugging the engine. At cruising speeds, even pulling moderate hills, there is virtually no drone.
Intermediate
Joined: Feb 2007
Posts: 30
Likes: 0
From: Columbia MO
Last weekend I installed Z06 dual mode mufflers. The previous owner had install mufflers that had a terrible drone and were extremely loud. Without vacuum the butterflies are open. It is still really quite. I picked up an NPP in a box that I will be installing today. I don’t think it will make much difference now, but once I have headers I will most likely need it.
Racer
Joined: Jan 2010
Posts: 289
Likes: 13
From: San Jose CA
Since your car didn't have the NPP from the factory, then you have many muffler options to choose from. Yes you can purchase all the NPP hardware and then run the system in the open all the time position. Be sure you purchase the hardware that fits the 2010 model. I have the NPP system and have pulled the fuse so it's open all the time. The drone on highway speed in 6th gear of my manual trans really bothers me, so mostly I drive in 5th. I should install a switch for this reason.
My California car came originally with two catalytic converters, and with the fuse pulled and the mufflers open all the time, the sound was glorious! Then we had a recall that required that CA cars need 4 cats. Now, Sound is slightly less glorious.
My advice regarding the other muffler options, would be to find your local Corvette club and check out someone's car with aftermarket non NPP mufflers, and choose the sound that you like the most.
My California car came originally with two catalytic converters, and with the fuse pulled and the mufflers open all the time, the sound was glorious! Then we had a recall that required that CA cars need 4 cats. Now, Sound is slightly less glorious.
My advice regarding the other muffler options, would be to find your local Corvette club and check out someone's car with aftermarket non NPP mufflers, and choose the sound that you like the most.