For what its worth, I wouldnt own a Corvette without NPP for the simple reason I can turn it "off" or "on" and make the car quieter again when either running on the highway or when trying to carry on a conversation, etc. You can change the settings by pulling the fuse, changing the driving mode, or buying a mild to wild switch or making your own.
Aftermarket exhausts are well liked by a lot of members here and they always mention they cost about the same. But they cant be switched on or off.
To each their own but make mine NPP.

 

Stingray, the NPP and non-NPP exaust are completely different, not just the valves.

The non NPP is a regular exhaust like any other car that has a single pipe exit. That single pipe has a tip that is split into two tips (one in each muffler) to make it look like a quad exhaust when in actuality it is just a dual exhaust with a splitter that splits the single tip into two tips.

The NPP exhaust actually has 4 separate tips, (2 in each muffler). Each muffler has a channel in it for each tip. One channel just bypasses the muffler while the other channel forces the air to go through the muffler. Hence the use of the valves to control the air flow.

 

It's what inside the muffler cans that count. NPP and non-NPP mufflers are totally different.

As was mentioned above, NPP mufflers are considerably louder w/ valves open. Non-NPP mufflers are much more muted even though they are always free-flowing, but you only have two pipes each with a dual tip. NPP is a 4 pipe system with different plumbing inside the can.

 

I love the NPP and the way it can change the character of the car. I let the driving mode determine the NPP settting. GM claims a 5HP gain with the open exhaust but you can't feel >1% in the seat of the pants.

Anyway, I ordered my car with NPP and after 3 years of ownership I can tell you I would definitely do it again, if that helps.

 

I believe with NPP you get bigger exhaust pipes versus the non-NPP set up... it's not just the valves.

 

Again, it's not just about valves. They are totally different mufflers.

 

Stingray, this is the standard (non NPP) exhaust. Just think of them as the standard exhaust you find on any other Chevrolet model. The dual tips comes from a single outlet on each exhaust can. The sound on this exhaust is much better than the Borla Touring exhaust I had on my C6, but not as loud as the NPP system.

 

Stingray, NPP gives you the option of being quiet or aggressive sounding. Each muffler has a dual mode controlled electronically with opening and closing valves. Basically it is like having two mufflers in one. The standard Non NPP exhaust is quiet all the time with no adjustment as a standard car muffler. The 4 tips on the non NPP exhaust are there for looks
only.

 

At idle there isn't much difference between open and not open sound as far as I am concerned. The difference between NPP mufflers and Non NPP mufflers is the amount of exhaust gas that can flow through them at any point. When the valves are open NPP Mufflers have a straight exhaust flow path through the muffler similar to the old fashioned Glass Packs. When they are closed the exhaust gases go through several chambers in the muffler that reduces flow rate and quiets them down. The Non NPP mufflers do not have a straight through path.

The advantage of the NPPs is the straight through path when you are on the throttle producing power Vs winging the throttle in the parking lot producing useless noise. They open up when you need max power operating at wide open throttle. Listen to a few PDR videos taken on track where people are running the car hard and you can hear the open exhaust as the car powers down a straight and is quiet at slow speeds and part throttle operation where the amount of exhaust flow is not all that high and the quiet flow path has plenty of flow capacity.

Here is a video from an autocross last July. You can hear the exhaust snarl when I am on the throttle and if you listen close you can hear it get raspy as I got on the throttle every now and then. The raspy noise happened when Performance Traction Management cut in to limit wheel spin to what the slicks could handle.

Noise when it means something and no noise when it doesn't mean anything.

Bill

 

Besides the functionality of NPP, the looks of the wider and flared pipes are worth the price.

 

Bottom line is, unless you just can't afford it, you will want NPP. It provides much better sound, the flexibility to control it and it even looks better. If you want to do it right, you should also swap in a Borla x-pipe. But that's a whole other thread.

 

I'm beginning to think mine have issues. Seems like anytime the car fluctuates between 4 cylinder and 8 cylinder mode, the valves have a hard time keeping up and the car makes a horrible "frapping" sound. I'm going to take it in and have it checked. 14 A6 for those wondering.

 

I believe this is correct.

NPP also supposedly gives you an extra 5 horsepower, which is negligible, almost certainly well within the usual production engine variation in power.

It gives you more noise under certain circumstances, but the standard exhaust sounds OK, also.

On a new car purchase you would have to factor in the increased cost. On a used car you won't be able to tell if it's costing you any more or not. My suspicion is that NPP cars are slightly more desirable to those who understand the option, so it might make a minor difference when you sell.

Conclusion: I wouldn't worry about it either way.

 

This is the best and simplest answer describing the difference between NPP and non-NPP.

 

Slightly? For most it is a must have.

 

Exactly.
The stock Stingray, without NPP, has only one outlet from each muffler that splits into two exhaust tips and no valves.

The NPP muffler has two outlets on each muffler. One has butterfly valve, the other is open. The advantage of the NPP muffler is that when the butterfly opens, the exhaust goes straight through and essentially bypasses the muffler.

 

I knew that I didn't want the NPP as I always add aftermarket set-ups, and the concept of adjusting the volume never appealed to me, but it came with the Z.

If you are planning to add an aftermarket exhaust, and you don't care about adjusting volume, then don't get it. If not, then absolutely get it.

It's way better than the bese set-up in both sound and appearance.

 

I thought the NPP would be aggressive enough for me with sound management off. But it wasn't so I added the Corsa X-pipe. Now it is better - pretty good gurgle and pop but not ideal. It really depends on how loud you like it and if the ability to modify the sound is important to you. In hindsight I would skip the NPP and go right to a cat back system. I had one on my C6 so maybe that is just what I am used to.

 

Had NPP on my 2012 GS and decided to not get in on my 2016 and spent $500 more on the Corsa and love it.

 

Good explanation.
For the OP, lack of NPP should NOT be a deal breaker!

I installed a simple switch in my NPP C6 (easier to do in a C6) to be able to keep the valves opened when "I wanted." Cruising on the highway I had to close the butterflys as there was an objectionable drone. Hench any mpg benefit (doubt it could be measured if there is any) was gone! Expect the same for the C7 and there have been some posts saying it was the case and the reason they could not just "pull the fuse."

In fact having installed FlowMaster muffles on an older Vette, Borla mufflers on my current ProSreet '34 BB with headers and FlowMasters on a recent S-10 truck I believe you can get a "better" overall sound (albeit subjective) with an aftermarket exhaust!

Folks like FlowMaster and Borla design systems that do not have significant drone and don't just open up a thru pipe as does NPP. With NPP they rely on not having the pipes wide open when cursing, even in Track mode, to avoid drone.

FWIW