NPP valves.
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,503
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From: Loveland
NPP valves.
For my 2014 A6 Stingray. I have the NPP valves. I understand in touring mode they are closed, and in sport mode they are supposed to be open. BUT, sometimes even in sport mode I can hear the quieter sound. This only happens when I am very light on the throttle. As soon as I get on the throttle they open. Is this normal? I thought in sport mode they were open all the time. Also, even in touring mode, when I shut down the engine, they open. I can see them closed with the engine running in touring mode. So I know they open and close.
My AFM valves have been tuned out.
My AFM valves have been tuned out.
Last edited by kodpkd; May 3, 2026 at 06:34 PM.
Drifting
Joined: Jul 2017
Posts: 1,370
Likes: 1,341
From: Kingston, Ontario
Normal, sport mode does not mean fully open all the time. Sport mode means it opens under specific conditions (like throttle) and stays open for a certain amount of time, like 10 seconds after you get off throttle and closes.
Track is the same, except it keeps them open for longer before closing.
Tour is closed until you give enough throttle to open them, but they will close after you get off throttle.
The NPP valves are never fully open all the time in any mode. The mode just determines how they open and how long they stay open before closing.
Track is the same, except it keeps them open for longer before closing.
Tour is closed until you give enough throttle to open them, but they will close after you get off throttle.
The NPP valves are never fully open all the time in any mode. The mode just determines how they open and how long they stay open before closing.
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,503
Likes: 2,202
From: Loveland
OK, whew, now I am going to try the touring mode when I floor it. Thank you. 
Took it for a drive. In track mode I could hear the, valves close sound, if I was in high gears and lug it a bit. As usual I couldn't find the reference in the manual.
Took it for a drive. In track mode I could hear the, valves close sound, if I was in high gears and lug it a bit. As usual I couldn't find the reference in the manual.
Last edited by kodpkd; May 3, 2026 at 07:55 PM.
Melting Slicks
Joined: Aug 2018
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From: Clermont, Florida
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Race Director
Joined: Dec 2005
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From: Carlsbad Ca
In "sport" mode, they'll open @3000RPM.
Melting Slicks
Joined: Jan 2017
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From: CONCORD CA.
Have you checked the engine management settings in the option screen? This is what allows you to control the operation of the NPP option.
Pulling the fuse is not necessary, unless you have a C6.
Pulling the fuse is not necessary, unless you have a C6.
Racer
Joined: Sep 2020
Posts: 423
Likes: 390
From: CO
Here's a discussion on NPP tuning using HPTuners.
https://www.corvetteforum.com/forums...questions.html
There are tables of what is set in the ECM for each mode. You'll need to read through the posts to get a better understanding, and it won't be for everyone.
https://www.corvetteforum.com/forums...questions.html
There are tables of what is set in the ECM for each mode. You'll need to read through the posts to get a better understanding, and it won't be for everyone.
Team Owner
Joined: Apr 2013
Posts: 26,255
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From: Chirper Island
The'14s only have an on/off option for engine sound management, unlike later years.
Eta when on, it is slaved to drive mode, when off it is open-ish. The range of loudness is not as wide as later years. It never gets as quiet as stealth or as loud as track on the later years.
Eta when on, it is slaved to drive mode, when off it is open-ish. The range of loudness is not as wide as later years. It never gets as quiet as stealth or as loud as track on the later years.
Last edited by owc6; May 4, 2026 at 01:01 PM.
Tech Contributor
Joined: Oct 1999
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From: Charlotte, NC (formerly Endicott, NY)
It may depend on the year, but it definitely depends on the transmission. Based on owner comments over the years, I believe the 2014 settings may be different from those in the following years.
My 2015 Z06/M7 has the following Engine Sound Management settings: Auto, Stealth, Tour, or Track. When I select Track, the valves are open except when the car is in 5th gear at engine speeds below 1500 rpm. One reason the valves will close is to reduce objectionable exhaust noise when the engine is operating in Eco Mode (4-cylinder mode). Cars having the A8 transmission run in Eco Mode all the time (don't know about the A6) except when the transmission is in Manual Mode, whereas cars with the M7 transmission, the driver has to select ECO mode with the driving mode selector on the console.
Bill
My 2015 Z06/M7 has the following Engine Sound Management settings: Auto, Stealth, Tour, or Track. When I select Track, the valves are open except when the car is in 5th gear at engine speeds below 1500 rpm. One reason the valves will close is to reduce objectionable exhaust noise when the engine is operating in Eco Mode (4-cylinder mode). Cars having the A8 transmission run in Eco Mode all the time (don't know about the A6) except when the transmission is in Manual Mode, whereas cars with the M7 transmission, the driver has to select ECO mode with the driving mode selector on the console.
Bill
Melting Slicks
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