NPP Cut away photos

GMGP5X · 10-26-2015, 06:04 AM

NPP muffler does not look as large as it does on photos I have seen on the car.

MaximumHP · 10-26-2015, 09:36 AM

hmm, interesting. It is pretty much straight through when the valve is open. when closed the exhaust must have to go through the perforations, into the center section through that pipe and then who knows what and eventually out through the other tip, that's a convoluted path.

rotis · 10-26-2015, 02:27 PM

Oh, wow. I'm kinda shocked at what it looks like inside. I can't believe the exhaust has to go through those perforations when the valves are closed. That explains why the manual says not to do any track driving with the exhaust in 'stealth' mode.

Sledgehammer70 · 10-27-2015, 02:39 AM

Interesting way to accomplish what they are doing.

Denis · 10-27-2015, 09:37 AM

oh wow....im wondering how restrictive that will be when the butterfly is closed. seems like there is going to be a jump in power between stealth mode and track mode.

joemosfet · 10-27-2015, 09:52 AM

Quote:

Originally Posted by Denis

seems like there is going to be a jump in power between stealth mode and track mode.

I really doubt it. If there is, it will be negligible, and you won't feel it. I doubt it would even show itself in a 1/4 mile.

NASTY99Z28 · 10-28-2015, 08:45 AM

Most aftermarket mufflers can varry between 5-10hp. After seeing this its hard to believe that you can't feel or see the difference between wide open and a few poked holes!!!!

LesserO2Evils · 10-28-2015, 11:00 AM

That is quite the interesting design. Nothing like what I envisioned in my mind.

Curr · 10-28-2015, 11:46 AM

That is complete unlike what I thought it looked like on the inside. Great post, thanks.
Love that it's a flat out muffler bypass open!

Hells yes.

DenverTaco07 · 10-28-2015, 12:49 PM

cool thanks! They should put an adobe flash illustration together, so we can see the flow.

I sort of get it (maybe?), when the flap is closed exhaust fills the void (all chambers) before escaping and obviously no exhaust exits via the outer two tips, when open the path of least resistance is the outer tips and seems to me that the majority of exhaust would then flow through the outer tips.

anyway, someone smarter than me please chime in.

Geno · 10-28-2015, 01:28 PM

Quote:

Originally Posted by rotis

Oh, wow. I'm kinda shocked at what it looks like inside. I can't believe the exhaust has to go through those perforations when the valves are closed. That explains why the manual says not to do any track driving with the exhaust in 'stealth' mode.

Any pictures of the stock, non NPP muffler inside? It would seem to me that design with pin holes would create terrible back pressure. I wonder if the standard muffler is engineered like that????

KMPrenger · 10-28-2015, 02:14 PM

Very interesting!

When closed, the exhaust comes out the perforated holes, into the wide open muffler space, and has to find its way out of that exhaust hole which routes to the pipe that comes out on the opposite side of the can.

Wow.

When open...it is pretty much straight through.

I would be a bit shocked of the NPP closed versus open isn't good for 5 - 10 HP.

Begs the question, do we get 455 HP at closed, or at full open (or maybe something inbetween? lol)

DenverTaco07 · 10-28-2015, 02:24 PM

Quote:

Originally Posted by KMPrenger

Very interesting!

When open...it is pretty much straight through.

But straight through dual exhaust...mostly, would you agree? I mean it's not straight thru quad exhaust although i'm sure some of the exhaust when wide open would still leak through the perforated holes and then find itself back out as you described, but my guess is that wide open 80 or 90% of the exhaust travels through the outer tips.

I admit I'm guessing based on no real knowledge on the issue though.

joemosfet · 10-28-2015, 02:47 PM

It is my opinion that the amount of flow between closed and open is negligible. The upstream catalytic converters are much more of a flow restrictor than the perforated and rerouted exhaust.

The picture doesn't really do it much justice, but I think if you were to see this in person, you would see that the path of flow, while convoluted, is still extremely free flowing. The amount of surface area provided by the perforated holes, when all added up, is likely near or even over the 2.5pi (assuming they're 2.5" pipes).

As free flowing as when the cutouts are open? No. Does it make a difference in power? Negligible. Maybe at high rpms the difference would show up on a dyno.

Now, of course all of my speculation is based on experience with several different exhaust systems, as well as knowledge about fluid dynamics, so I could be completely wrong. And, if they were to fill the empty spaces in the muffler with rockwool or fiberglass (often used to increase sound dampening capabilities) my opinion might be a bit different.

10-26-2015, 06:04 AM	#1
GMGP5X Drives: 2011 2LT RS VR 2008 Silverado 2500 Join Date: Sep 2010 Location: Florissant,Mo Posts: 580 View My Garage	NPP Cut away photos NPP muffler does not look as large as it does on photos I have seen on the car. Attached Images __________________ 2LT RS VR / ARK DTS Cat back exhaust / Roto-Fab CAI / RPI stealth mud guards /Defender works billet chrome door sills/ DIY painted engine cover, trunk corners, and brake rotors / RX catch can / Team LLT badges. Team LLT

10-27-2015, 02:39 AM	#4
Sledgehammer70 Lethal Camaro Drives: 16 2SS, 71 Std, Suburban RTS Join Date: Jun 2013 Location: Temecula, CA Posts: 3,855 View My Garage	Interesting way to accomplish what they are doing. __________________ Thanks My Build Thread \| Lethal Garage YouTube \| Lethal Camaro IG \|

10-27-2015, 09:37 AM	#5
Denis Drives: 2010 SS Join Date: May 2012 Location: Yorktown Heights, NY Posts: 7,695 View My Garage	oh wow....im wondering how restrictive that will be when the butterfly is closed. seems like there is going to be a jump in power between stealth mode and track mode. __________________

10-28-2015, 08:45 AM	#7
NASTY99Z28 Drives: 99z28 with bolt-ons and a mwc fab 9 Join Date: Jul 2012 Location: Florida Posts: 1,277	Most aftermarket mufflers can varry between 5-10hp. After seeing this its hard to believe that you can't feel or see the difference between wide open and a few poked holes!!!! __________________ I like my woman like my milk shakes, THICK!!!!

10-28-2015, 11:00 AM	#8
LesserO2Evils GM repeat offender... Drives: 16 2SS Join Date: Dec 2014 Location: Grandview, Texas Posts: 1,474	That is quite the interesting design. Nothing like what I envisioned in my mind. __________________ '16 2SS, Summit White. A8. MRC. NPP. Ordered:09/03/15. Received 12/22/15 INCOMING: ‘22 ZL1, Satin Steel. A10. PDR. Ordered: 03/02/22.

10-26-2015, 09:36 AM	#2
MaximumHP Drives: 06 GTO Join Date: Jul 2015 Location: Appleton Posts: 3	hmm, interesting. It is pretty much straight through when the valve is open. when closed the exhaust must have to go through the perforations, into the center section through that pipe and then who knows what and eventually out through the other tip, that's a convoluted path.

10-26-2015, 02:27 PM	#3
rotis Drives: 2019 ZL1 1LE Join Date: Sep 2010 Location: Bastrop, TX Posts: 441	Oh, wow. I'm kinda shocked at what it looks like inside. I can't believe the exhaust has to go through those perforations when the valves are closed. That explains why the manual says not to do any track driving with the exhaust in 'stealth' mode.

10-28-2015, 11:46 AM	#9
Curr Probably doesn't like you Drives: 2022 WCT ZL1 M6 Join Date: Jun 2015 Location: Boston-ish Posts: 1,382	That is complete unlike what I thought it looked like on the inside. Great post, thanks. Love that it's a flat out muffler bypass open! Hells yes. __________________ I hope the 6th gen Camaro has a melodious horn trumpet. I'll tootel it at the ladies, yelling out "Hi hi." - RenegadeXR كافر ΜΟΛΩΝ ΛΑΒΕ железобетонное очко Quod gratis asseritur, gratis negatur. There is an unequal amount of good and bad in most things, the trick is to work out the ratio and act accordingly.

10-28-2015, 12:49 PM	#10
DenverTaco07 Drives: 2017 SS 1LE, 2017 Volt, 2013 Pilot Join Date: May 2014 Location: Colorado Posts: 4,274	cool thanks! They should put an adobe flash illustration together, so we can see the flow. I sort of get it (maybe?), when the flap is closed exhaust fills the void (all chambers) before escaping and obviously no exhaust exits via the outer two tips, when open the path of least resistance is the outer tips and seems to me that the majority of exhaust would then flow through the outer tips. anyway, someone smarter than me please chime in. __________________ 2017 SS 1LE \| HBM \| Vortech V3-Si supercharger (620RWHP and 575ft lbs) \| PDR \| Black Bowties \| Illuminated Front Black Bowtie \| Illuminated Door Sills \| Smoked Tails \| vented seats mod Last edited by DenverTaco07; 10-28-2015 at 01:09 PM.

10-28-2015, 02:14 PM	#12
KMPrenger Drives: 16 Camaro SS, 15 Colorado Join Date: May 2009 Location: Jefferson City, Missouri Posts: 13,967	Very interesting! When closed, the exhaust comes out the perforated holes, into the wide open muffler space, and has to find its way out of that exhaust hole which routes to the pipe that comes out on the opposite side of the can. Wow. When open...it is pretty much straight through. I would be a bit shocked of the NPP closed versus open isn't good for 5 - 10 HP. Begs the question, do we get 455 HP at closed, or at full open (or maybe something inbetween? lol) __________________ 2016 Camaro 1SS - 8-speed - NPP - Black bowties 2010 Camaro 1LT V6 (Sold. I will miss her!)

10-28-2015, 02:47 PM	#14
joemosfet Drives: 2014 Camaro SS Join Date: Mar 2014 Location: Colorado Posts: 1,006	It is my opinion that the amount of flow between closed and open is negligible. The upstream catalytic converters are much more of a flow restrictor than the perforated and rerouted exhaust. The picture doesn't really do it much justice, but I think if you were to see this in person, you would see that the path of flow, while convoluted, is still extremely free flowing. The amount of surface area provided by the perforated holes, when all added up, is likely near or even over the 2.5pi (assuming they're 2.5" pipes). As free flowing as when the cutouts are open? No. Does it make a difference in power? Negligible. Maybe at high rpms the difference would show up on a dyno. Now, of course all of my speculation is based on experience with several different exhaust systems, as well as knowledge about fluid dynamics, so I could be completely wrong. And, if they were to fill the empty spaces in the muffler with rockwool or fiberglass (often used to increase sound dampening capabilities) my opinion might be a bit different. __________________ SOLD: 2014 Camaro Coupe 2SS/RS M6 Blue Ray Metallic, NPP, Nav 2014 Stingray Premiere Edition Coupe #142/500 Z51 3LT M7 Laguna Blue, Magride, NPP, Exposed Carbon Fiber Roof, Carbon Fiber Dash, Suede Wrapped Interior Canceled: 2016 Camaro Coupe 1AK37 2SS Coupe, G7E Garnet Red, BRJ Adrenaline Red Trim, F55 Magnetic Ride, NPP Exhaust, CF5 Sunroof, 56R Gray Split spoke w/ machined face, RN2 LPO Illuminated Bowtie, VYW Premium Floor Mats, W2D LPO Cargo Net

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