NNP Exhaust
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Yes but WHY ?? You can find some used ones online for maybe $600 so after installation you may still have $850 in it--You'd be better off to buy an aftermarket cat-back exhaust system for just a little more and have a better sounding car plus another 5-8 RWHP--
Better yet do a muffler delete as I did and install the Flowmaster dual 4" tips---I spent only $150 for this mod and the car sounds awesome----And no drone or annoying resonance during cruise--But mash the throttle and wow--It's incredible
Better yet do a muffler delete as I did and install the Flowmaster dual 4" tips---I spent only $150 for this mod and the car sounds awesome----And no drone or annoying resonance during cruise--But mash the throttle and wow--It's incredible
Safety Car
Joined: Jan 2006
Posts: 3,940
Likes: 42
From: shavertown Pa.
The problem with this new dual mode exhaust is that it isn't like the old one.
You can put the mufflers on, but I doubt you will be able to control them without the proper system that controls their operation.
I think it would be much more cost effective if you bought a muffler system that had a sound that appealed to you.
You can put the mufflers on, but I doubt you will be able to control them without the proper system that controls their operation.
I think it would be much more cost effective if you bought a muffler system that had a sound that appealed to you.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
On a C7 you are able to permanently delete the closed NPP exhaust system on your center dash screen--This will make the 2 exhaust butterflies stay OPEN all the time regardless if the AFM is activated or not and regardless if you are at WOT or not
Safety Car
Joined: Jan 2015
Posts: 3,941
Likes: 499
From: Northern Virginia
It has been documented repeatedly that even if you set NPP "off" (on a 2014) or to track (2015 & 16), the valves still close under some conditions. Specifically, at speeds under about 37 mph in 4th and 5th (on an M7). The same thing happens on an A6 or A8, but I'm not sure of the corresponding gears. This is done to pass federal sound tests, which are made at 35 mph in the highest gears that will support that speed.
Then there's the fact that there are FOUR exhaust valves, not two. The rearmost ones, that you can see, are what we commonly call the NPP valves and are controlled by the ESM setting in the dash screen (with the limitation described above). The other two are upstream of the mufflers, and operate when the engine goes into 4 cyl mode, regardless of how you have the NPP valves set.
Even when the NPP valves are open, when the engine goes into 4 cyl mode and the AFM valves close (partially) the exhaust gets quieter.
On the A8 and A6, the engine will go into 4 cylinder mode, operating the AFM valves, even when you're not in Eco mode (unless you put the transmission into manual mode).
Finally, since this thread is about adding the NPP exhaust to a car that didn't come with it, the non NPP cars won't have the wiring to let you use the dash to control the NPP valves. People have tried, and there's just no simple way to add NPP valves to a car that didn't come with that exhaust.
Last edited by meyerweb; Aug 14, 2015 at 03:14 PM.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Well no, not really.
It has been documented repeatedly that even if you set NPP "off" (on a 2014) or to track (2015 & 16), the valves still close under some conditions. Specifically, at speeds under about 37 mph in 4th and 5th (on an M7). The same thing happens on an A6 or A8, but I'm not sure of the corresponding gears. This is done to pass federal sound tests, which are made at 35 mph in the highest gears that will support that speed.
Then there's the fact that there are FOUR exhaust valves, not two. The rearmost ones, that you can see, are what we commonly call the NPP valves and are controlled by the ESM setting in the dash screen (with the limitation described above). The other two are upstream of the mufflers, and operate when the engine goes into 4 cyl mode, regardless of how you have the NPP valves set.
Even when the NPP valves are open, when the engine goes into 4 cyl mode and the AFM valves close (partially) the exhaust gets quieter.
On the A8 and A6, the engine will go into 4 cylinder mode, operating the AFM valves, even when you're not in Eco mode (unless you put the transmission into manual mode).
Finally, since this thread is about adding the NPP exhaust to a car that didn't come with it, the non NPP cars won't have the wiring to let you use the dash to control the NPP valves. People have tried, and there's just no simple way to add NPP valves to a car that didn't come with that exhaust.
It has been documented repeatedly that even if you set NPP "off" (on a 2014) or to track (2015 & 16), the valves still close under some conditions. Specifically, at speeds under about 37 mph in 4th and 5th (on an M7). The same thing happens on an A6 or A8, but I'm not sure of the corresponding gears. This is done to pass federal sound tests, which are made at 35 mph in the highest gears that will support that speed.
Then there's the fact that there are FOUR exhaust valves, not two. The rearmost ones, that you can see, are what we commonly call the NPP valves and are controlled by the ESM setting in the dash screen (with the limitation described above). The other two are upstream of the mufflers, and operate when the engine goes into 4 cyl mode, regardless of how you have the NPP valves set.
Even when the NPP valves are open, when the engine goes into 4 cyl mode and the AFM valves close (partially) the exhaust gets quieter.
On the A8 and A6, the engine will go into 4 cylinder mode, operating the AFM valves, even when you're not in Eco mode (unless you put the transmission into manual mode).
Finally, since this thread is about adding the NPP exhaust to a car that didn't come with it, the non NPP cars won't have the wiring to let you use the dash to control the NPP valves. People have tried, and there's just no simple way to add NPP valves to a car that didn't come with that exhaust.
On a C7 you are able to permanently delete the closed NPP exhaust system on your center dash screen--This will make the 2 exhaust butterflies stay OPEN all the time regardless if the AFM is activated or not and regardless if you are at WOT or not
I meant----On a NPP equipped car you can keep the NPP valves in the mufflers open all the time using the in dash settings under sound management
The forward butterfly valves close somewhat when the AFM is activated--- TO keep the front butterflies OPEN all the time you would need to DELTE the AFM system in your tune
I have No mufflers on my car--so it is really easy to tell if the front butterflies are either closed or opened---- I have deleted the AFM in my tune and I have never heard those valves close ever again--Not even below 35 MPH and in any gear---
The
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
Tblu92, this is still not correct WRT the NPP valves. Your AFM summary is spot on. The AFM valves only actuate closed during V4 operation.
Meyerweb is 100% correct on the NPP valve function. The NPP valves do NOT remain open all the time even with Engine Sound Management (ESM) in the vehicle settings set to Off (2014) or Track (2015). They still actuate CLOSED under certain conditions even when ESM is set to "Off/Track". (NOT AFM related), and Meyerweb covered well it in summary. The ONLY way to keep NPP valves open all the time is by pulling the NPP fuse...at the cost of losing on the fly control in the settings.
Please read the following threads as well as many others that cover the misconceptions an misunderstandings in NPP valve function on the C7.
https://www.corvetteforum.com/forums...ck-result.html
https://www.corvetteforum.com/forums...e-control.html
https://www.corvetteforum.com/forums...-retrofit.html
Meyerweb is 100% correct on the NPP valve function. The NPP valves do NOT remain open all the time even with Engine Sound Management (ESM) in the vehicle settings set to Off (2014) or Track (2015). They still actuate CLOSED under certain conditions even when ESM is set to "Off/Track". (NOT AFM related), and Meyerweb covered well it in summary. The ONLY way to keep NPP valves open all the time is by pulling the NPP fuse...at the cost of losing on the fly control in the settings.
Please read the following threads as well as many others that cover the misconceptions an misunderstandings in NPP valve function on the C7.
https://www.corvetteforum.com/forums...ck-result.html
https://www.corvetteforum.com/forums...e-control.html
https://www.corvetteforum.com/forums...-retrofit.html
Last edited by xp800; Aug 15, 2015 at 08:29 PM.
Safety Car
Joined: Jan 2015
Posts: 3,941
Likes: 499
From: Northern Virginia
Thanks XP800.
If one really wants to pull the fuse, but still be able to turn track mode off on the fly, there is a relatively simple mod:
https://www.corvetteforum.com/forums...e-control.html
tblu, the 35 mph cutoff isn't the AFM valves, it's the NPP valves (which you no longer have).
If one really wants to pull the fuse, but still be able to turn track mode off on the fly, there is a relatively simple mod:
https://www.corvetteforum.com/forums...e-control.html
tblu, the 35 mph cutoff isn't the AFM valves, it's the NPP valves (which you no longer have).
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