NPP fuse pull trick/result
Safety Car
Joined: Dec 2003
Posts: 4,240
Likes: 1,879
From: USA
I've had my new C7 since last Friday and the first thing I did after I got it home was pull the Fuse 41. I have an automatic and I set the Sound Management to Off, but I still notice driving around town sometimes at low speeds(between approximately the 1000-1700 RPM range) that the exhaust will suddenly go from loud to silent, but then as soon as you dip in the throttle a little bit it gets loud again. Is this normal?
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
With the A6, you may be going into V4 mode. Change your center display to Info and choose the screen that shows you V8/V4 and compare that to the sound you hear.
Fuse 41 is the only fuse for the NPP valves (Theta's schematic shows this too).
Fuse 41 is the only fuse for the NPP valves (Theta's schematic shows this too).
Safety Car
Joined: Dec 2003
Posts: 4,240
Likes: 1,879
From: USA
I had the car in Sport when I noticed this so should it be going into V4 mode at low RPMs even when running in Sport?
Safety Car
Joined: Dec 2003
Posts: 4,240
Likes: 1,879
From: USA
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
Originally Posted by BMadden
Thanks, xp800. So, it's going into V4 mode when I'm driving it in regular automatic and that's why it goes silent at the low RPMs, correct? If I was using the paddle shifters I'm assuming that wouldn't be an issue. 
Drifting
Joined: May 2001
Posts: 1,670
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From: Charlotte NC
I posted in the general discussion forum that my C7 while driving in Sport or Track mode is not as loud as my C6 with the Mild to Wild/Wild setting on. So what you're saying is that to get the sound I want (which is loud all the time), all I have to do is pull the Fuse 41?
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Racer
Joined: Sep 2004
Posts: 493
Likes: 109
From: Central California
I posted in the general discussion forum that my C7 while driving in Sport or Track mode is not as loud as my C6 with the Mild to Wild/Wild setting on. So what you're saying is that to get the sound I want (which is loud all the time), all I have to do is pull the Fuse 41?
Drifting
Joined: May 2001
Posts: 1,670
Likes: 0
From: Charlotte NC
I'm in the same boat as you, and unfortunately, pulling fuse 41 will not satisfy you. Maybe it's my car but the exhaust always quiet down unless you step on it. With the fuse pulled, at least when you step on it the sound is louder even under 1700rpm. But at idle it will not be anything like when you initially start up the engine. I'm still disappointed with the sound at idle.
Is it the switch to V4 that is causing this problem?
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
Candy and vincent,
In A6 cars, I think the V4 mode is the most likely explanation for the lack of good noise since most of the time you would be driving in modes where V4 can happen a lot.
I took a 300 mile trip yesterday, and drove about half in Eco. In the M7 and no #41, the transition between V4/8 on the highway is very noticeable in sound (and a slight lurch). In V8 mode the engine note is very pronounced all the time even at highway speed. In V4 it's almost silent from the front valves (and without #41 the NPP valves are open).
I guess the only way to replicate this in the A6 is to paddle shift. Try it to see if it changes your sound, especially as you're cruising in a gear and gently tip in. If you're in V8 mode the noise will already be there and increase as you would expect on tip in. If you're in V4 you would go quiet to louder like a switch. Or monitor the V4/V8 indicator to see if it matches quiet/loud respectively.
In A6 cars, I think the V4 mode is the most likely explanation for the lack of good noise since most of the time you would be driving in modes where V4 can happen a lot.
I took a 300 mile trip yesterday, and drove about half in Eco. In the M7 and no #41, the transition between V4/8 on the highway is very noticeable in sound (and a slight lurch). In V8 mode the engine note is very pronounced all the time even at highway speed. In V4 it's almost silent from the front valves (and without #41 the NPP valves are open).
I guess the only way to replicate this in the A6 is to paddle shift. Try it to see if it changes your sound, especially as you're cruising in a gear and gently tip in. If you're in V8 mode the noise will already be there and increase as you would expect on tip in. If you're in V4 you would go quiet to louder like a switch. Or monitor the V4/V8 indicator to see if it matches quiet/loud respectively.
Racer
Joined: Sep 2004
Posts: 493
Likes: 109
From: Central California
Thank you, Xp800. Actually I have an m7. However I think we are talking loudness level in terms of relativity. I came from a viper SRT so I am used to a much louder, but not as nice sounding exhaust than my c7. I actually think the interior may be too padded to insulate noise. I was driving behind in another car while my son was driving my c7, and it was quite loud.
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
Thank you, Xp800. Actually I have an m7. However I think we are talking loudness level in terms of relativity. I came from a viper SRT so I am used to a much louder, but not as nice sounding exhaust than my c7. I actually think the interior may be too padded to insulate noise. I was driving behind in another car while my son was driving my c7, and it was quite loud.
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
http://forums.corvetteforum.com/1586629378-post78.html
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
Based on the labeling on the fuse box lid and Theta's schematic (below), I'd say no.
http://forums.corvetteforum.com/1586629378-post78.html
http://forums.corvetteforum.com/1586629378-post78.html
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
Yep. Unless you're hoping for always having the cold-start sound that was discussed in another thread. That first loud bark comes from changes in the metal, etc.
The #41 fuse pull will keep the valves open constantly.
The #41 fuse pull will keep the valves open constantly.
Instructor
Joined: Oct 2007
Posts: 244
Likes: 3
I pulled fuse 41 and started it up. It was already warmed up from a previous ride with the exhaust setting off. I could not tell a lot of difference just parked in the garage, but will have to go for another ride. I have read the entire thread. If I understand correctly, when the car normally started up, the npp valves were open, but shut immediately upon starting with fuse 41 in. Now that the fuse is removed, the npp valve stay normally open all the time. With the fuse in, you had to be above 1700 rpm for the npp valves to progressively open even with the exhaust setting off. Hopefully, I have got it right, if not, let me know where I am wrong.