NP not opening ?
Thread Starter
Instructor
Joined: Apr 2014
Posts: 162
Likes: 0
From: Moreno Valley CA
NPP not opening ?
So before I took delivery I've been on here for a few months and read different threads about npp exhaust. I have an A6 with npp. I turned off sound management so that the valves would stay open. I know if you use the auto in D that it will go into 4 cylinder mode, but I've been using it Manual mode for the break in. I was looking at the exhaust and it looks like only the two outer exhaust tips have condensation stains andinner ones don't. I looked straight back into the pipe and I can see the two inner butterflies are closed. Shouldn't they be open ? if I'm using it in manual + sport mode shouldn't it be open?
Last edited by djlink21; Aug 2, 2014 at 12:36 AM. Reason: typo
Le Mans Master
Joined: Oct 2004
Posts: 8,615
Likes: 60
From: Haymarket Virginia
If you have Engine Sound Management, the NPP should be open 95% of the time.
100% of the time at idle and when cruising at lower RPMs and when V4 is kicked on they will be closed. All other times they are open.
You should notice a big sound change when they are open.
The exhaust tips that don't have valves do stay cleaner.
Go into your menu and turn engine sound management to auto then to off, see if you can hear a difference.
100% of the time at idle and when cruising at lower RPMs and when V4 is kicked on they will be closed. All other times they are open.
You should notice a big sound change when they are open.
The exhaust tips that don't have valves do stay cleaner.
Go into your menu and turn engine sound management to auto then to off, see if you can hear a difference.
Le Mans Master
Joined: Dec 1999
Posts: 6,516
Likes: 4,840
From: One Hour From Boston!
Wow. Lots of confusion here. The middle two pipes are not closed, they are muffled and they are muffled 100% of the time. There are no butterfly valves inside the middle two pipes. The outer two pipes are connected to straight pipes (unmuffled) and have butterfly valves inside the pipes at the exhaust tips. These butterfly valves when closed force the exhaust gases to exit through the inner muffled pipes to create a quiet muffled sound. When the butterfly valves located inside the outer pipes open, the exhaust gases exit through the outer pipes, taking the path of least resistance, and you hear the louder unmuffled sound. Therefore, if you drive around with the valves open most of the time, then soot will collect mostly on the outer two exhaust tips.
Team Owner
Joined: Aug 2007
Posts: 136,140
Likes: 2,432
From: I live my life by 2 rules. 1) Never share everything you know. 2)
St. Jude Donor '11-'12-'13, '16-'17-'18
Wow. Lots of confusion here. The middle two pipes are not closed, they are muffled and they are muffled 100% of the time. There are no butterfly valves inside the middle two pipes. The outer two pipes are connected to straight pipes (unmuffled) and have butterfly valves inside the pipes at the exhaust tips. These butterfly valves when closed force the exhaust gases to exit through the inner muffled pipes to create a quiet muffled sound. When the butterfly valves located inside the outer pipes open, the exhaust gases exit through the outer pipes, taking the path of least resistance, and you hear the louder unmuffled sound. Therefore, if you drive around with the valves open most of the time, then soot will collect mostly on the outer two exhaust tips.
Thank you. Saved me some typing 
Thread Starter
Instructor
Joined: Apr 2014
Posts: 162
Likes: 0
From: Moreno Valley CA
Wow. Lots of confusion here. The middle two pipes are not closed, they are muffled and they are muffled 100% of the time. There are no butterfly valves inside the middle two pipes. The outer two pipes are connected to straight pipes (unmuffled) and have butterfly valves inside the pipes at the exhaust tips. These butterfly valves when closed force the exhaust gases to exit through the inner muffled pipes to create a quiet muffled sound. When the butterfly valves located inside the outer pipes open, the exhaust gases exit through the outer pipes, taking the path of least resistance, and you hear the louder unmuffled sound. Therefore, if you drive around with the valves open most of the time, then soot will collect mostly on the outer two exhaust tips.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Team Owner
Joined: Sep 1999
Posts: 20,054
Likes: 44
From: Swansea IL
But I can tell you the C7 NPP sounds a lot better than the C6 version. My last Vette was an 07 Z06 and at WOT it sounded raspy and when I heard Z06's at the track compared to say a Borla or B&B I put the fuse back in.
But the C7 NPP even with the A6 is perfect. GM did some extra tuning and got it right.
Drifting
Joined: Sep 2012
Posts: 1,443
Likes: 116
From: No Longer in CA! NV
Just curious, but why would you force manual mode for break in? Chevy did a great job IMHO with their engine management, especially for the break in period, and I'm curious why you feel that you can do better than the computer?
Burning Brakes
Joined: Jun 2014
Posts: 981
Likes: 157
I'd say almost everything inside the muffler could be removed. Just use a die grinder with a very thin blade to cut open the wrap, use a plasma cutter to carve out the baffles and tubes, and then weld it back up. It would be a challenging project....welding thin stainless can be tricky.
