Npp
Thread Starter
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
Npp
Hey Guys,
I need some clarifications on NPP. I really want to understand NPP and what it all means. So the questions below will need some details to be answered. Thanks .
I think I understand NPP changes the sound of the exhaust by opening and closing valves, essentially making the exhaust open (like straight headers by bypassing the mufflers?) or muffled. Here are some of my questions:
1.) I read somewhere that non-NPP only use two of the four exhaust pipes. Is this true? If yes, does it really matter? If 8 pistons are funneled down to four pipes anyway, would narrowing it down to two make that big of a deal? I understand that causes a loss of some HP but how much are you really loosing?
2.) I understand that you can pull the fuse for NPP and the valves will remain open all the time. So is this option available for non-NPP cars? (this assumes the tech is installed on non-npp cars but you can't control it)
3.) I have read some on here that the valves are closed for eco mode for cylinder deactivation. Why? What would removing the fuse do to eco mode then?
4.) Can someone post NPP pic of the exhaust pipes vs non-NPP and a video of the NPP installed sound vs non-NPP?
Thanks
I need some clarifications on NPP. I really want to understand NPP and what it all means. So the questions below will need some details to be answered. Thanks .
I think I understand NPP changes the sound of the exhaust by opening and closing valves, essentially making the exhaust open (like straight headers by bypassing the mufflers?) or muffled. Here are some of my questions:
1.) I read somewhere that non-NPP only use two of the four exhaust pipes. Is this true? If yes, does it really matter? If 8 pistons are funneled down to four pipes anyway, would narrowing it down to two make that big of a deal? I understand that causes a loss of some HP but how much are you really loosing?
2.) I understand that you can pull the fuse for NPP and the valves will remain open all the time. So is this option available for non-NPP cars? (this assumes the tech is installed on non-npp cars but you can't control it)
3.) I have read some on here that the valves are closed for eco mode for cylinder deactivation. Why? What would removing the fuse do to eco mode then?
4.) Can someone post NPP pic of the exhaust pipes vs non-NPP and a video of the NPP installed sound vs non-NPP?
Thanks
Thread Starter
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
Race Director
Joined: Sep 2013
Posts: 11,825
Likes: 2,479
From: Ft Lauderdale
Tech Contributor
the are no controls with non NPP...it's the way it is all the time
all NPP controls are in the driving mode setting area - you can have the NPP follow the driving modes, or lock it open all the time - that's your only two choices.
And even when Locked open, they shut (some or all,not sure ) at highway speeds in any mode...
all NPP controls are in the driving mode setting area - you can have the NPP follow the driving modes, or lock it open all the time - that's your only two choices.
And even when Locked open, they shut (some or all,not sure ) at highway speeds in any mode...
Last edited by Glen e; Jan 5, 2014 at 08:39 PM.
Moderator
Joined: Feb 2006
Posts: 39,197
Likes: 18,055
From: DFW Area TX
Hey Guys,
I need some clarifications on NPP. I really want to understand NPP and what it all means. So the questions below will need some details to be answered. Thanks .
I think I understand NPP changes the sound of the exhaust by opening and closing valves, essentially making the exhaust open (like straight headers by bypassing the mufflers?) or muffled. Here are some of my questions:
1.) I read somewhere that non-NPP only use two of the four exhaust pipes. Is this true? If yes, does it really matter? If 8 pistons are funneled down to four pipes anyway, would narrowing it down to two make that big of a deal? I understand that causes a loss of some HP but how much are you really loosing?
...
Thanks
I need some clarifications on NPP. I really want to understand NPP and what it all means. So the questions below will need some details to be answered. Thanks .
I think I understand NPP changes the sound of the exhaust by opening and closing valves, essentially making the exhaust open (like straight headers by bypassing the mufflers?) or muffled. Here are some of my questions:
1.) I read somewhere that non-NPP only use two of the four exhaust pipes. Is this true? If yes, does it really matter? If 8 pistons are funneled down to four pipes anyway, would narrowing it down to two make that big of a deal? I understand that causes a loss of some HP but how much are you really loosing?
...
Thanks
Safety Car
Joined: Dec 2003
Posts: 3,641
Likes: 2,691
From: Pacific Northwest
Not financially reasonable, maybe not possible, as so many of the car's electronics and mechanical systems are tied into it. However, there are already some aftermarket systems that similarly have the ability to adjust the sound level from within the car.
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Moderator
Joined: Feb 2006
Posts: 39,197
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From: DFW Area TX
There are actually 2 sets of valves on NPP and one on non-NPP. One set operates during ECO mode and on the NPP the other valves control the sound volume (and cause the extra 5 HP when open). The ECO valves are to control the sound when operating in ECO mode (they make it sound better than it would without them while operating on only 4 cylinders).
Drifting
Joined: Sep 2013
Posts: 1,505
Likes: 13
Actually, the mufflers are completely different between the 2. The stock system has 2, 1 in, 1 out mufflers with a Y pipe on the back to 2 tips per muffler. The NPP has 2, 1 in, 2 out mufflers with special baffling to take advantage of the two outer exhaust pipes, which have the butterfly valves. When the butterfly is open it's a full 1 in, 2 out system. With the butterfly closed it's a 1 in, 1 out pipe and you only get exhaust out of the 2 center tips.
It's a very sophisticated system and worth every penny Chevy charges IMHO. Ordering the car without it with the expectation if doing aftermarket is just throwing good money after bad but YMMV.
It's a very sophisticated system and worth every penny Chevy charges IMHO. Ordering the car without it with the expectation if doing aftermarket is just throwing good money after bad but YMMV.
Thread Starter
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
Thanks for the pictures. That helps.
So in a non-NPP car, what is done to the two outer tips? Since the valves are not there are they permanently closed, open, partially blocked....
So in a non-NPP car, what is done to the two outer tips? Since the valves are not there are they permanently closed, open, partially blocked....
Moderator
Joined: Feb 2006
Posts: 39,197
Likes: 18,055
From: DFW Area TX
No, as mjw930 stated in his post, the non-NPP has two tips that are from a Y pipe (one inlet, one outlet that splits with a Y into two tips on each muffler).
Drifting
Joined: Sep 2013
Posts: 1,505
Likes: 13
I guess you didn't read my post. Each stock muffler has one exhaust pipe and a "Y" connection to 2 tips. 2 mufflers = 4 tips.
Drifting
Joined: Nov 2013
Posts: 1,329
Likes: 1
...and this is what NPP sounds like open:-) Turn up your volume because it was recorded without automatic gain control for more dynamics:
2014 C7 Corvette Sound - NPP in Sport Mode - YouTube
2014 C7 Corvette Sound - NPP in Sport Mode - YouTube
Thread Starter
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
I'm sorry. I did read it, I was so caught up with trying to figure it out after I saw the pictures, I forgot to go back and reread some things now that I had the visual.
Thanks for the input.