Question: Installation of GM Performance Z/28 exhaust, part no. 22906768 - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

sports car fan · 10-02-2024, 05:41 PM

Hi,

I am looking to upgrade to a dual mode exhaust system, while trying to stick to using original GM equipment. Even though they seem to be impossible to find any more.

One option would be the Z/28 exhaust system, part no. 22906768. I believe this is a system with exhaust flaps. My question is if anyone knows how the flaps are actuated? If there is some kind of control mechanism / electronic control, how would these be controlled on my 2011 car, which I suppose was never intended to have an exhaust system with flaps installed?

Another question is, would this exhaust system fit with the 1LE rear diffuser, part no. 22815277?

And last, I have read a few times about an "NPP" exhaust system, part no. 22756148. Can anyone inform me what NPP stands for and what the difference is to the afore mentioned Z/28 system?

Lastly, if anyone knows of anyone who has a set of the Z/28 exhaust lying around, it would be much appreciated!

Thank you for any help!

Joe.G · 10-02-2024, 06:43 PM

I'll try to answer some of your questions,

Z/28 exhaust is an NPP exhaust it is just a 1/4 inch bigger pipe size I believe.

the 1LE Diffuser will work if it is for a NPP equipped model.

As far as making the NPP Valve work there is a thread if you do a search.

CamaroCracka · 10-02-2024, 08:08 PM

Z28s that get totaled get parted out and I don't imagine anyone is selling one off a running Z28 given their collectability.

I just sold the mufflers off a 1LE NPP system and kept the rest of the exhaust for the future. Given you are in Europe, you will only want to ship the axle back portion. There is nothing special about it besides mufflers. The additional muffler opening is actuated by engine vacuum. You would also need a diffuser meant for quad tipped exhaust, i.e. not the one with big round openings.

There are aftermarket companies that sell an NPP style muffler, but they are not OEM.

olblue75 · 10-02-2024, 09:27 PM

So I have a 2010 SS with a 1LE diffuser with a z28 exhaust system, so like others have said it’s a 2 3/4 system but the mufflers are the same as a ZL1/1LE 2 1/2 inch, the valves are vacuum operated. NPP is just a code like 1LE Z28 etc etc.
Also I installed a C7 Corvette X replacing the Y portion of the exhaust sounds really good with headers and HF cats.

Send me a PM an I’ll send you a sound clip.

Joe.G · 10-02-2024, 09:42 PM

Olblue did the sound change between the H and the X pipe? The system necks down at the mufflers?

acutron42 · 10-03-2024, 05:39 AM

Here is a link to the system I am installing. I was lucky to find a oem 1LE quad tip diffuser & set of ZL1 mufflers. With this setup, I will have control of the actuators with a switch.

https://www.corvetteforum.com/forums...ne-intake.html

sports car fan · 10-03-2024, 03:11 PM

Wow, once again a lot of good information, thank you to everyone for replying!
Yes, I guess I will have to look if I can find a second-hand system somewhere.
Currently I have the GM Performance muffler 92206992 installed, which is the system with one tailpipe on each end, without the valves. I do like the sound - other than a horrible drone between 1200 and 2000 rpm - but I am hoping more can be extracted sound-wise with an alternative system.

WHAMMO · 10-09-2024, 11:36 AM

I have a 1LE and the stock NPP catback is extremly potent, good to 650hp np. I wanted to upgrade to a full 3inch dual and not have too much of a bottle neck at the mufllers so I found Z28 mufflers on ebay or here, not sure. Got a crazy deal on em. I still have my stock NPP catback hanging on my garage wall, not for sale LOL.

Z28 are 2.75'' and SS/1LE NPP are 2.5''. same vacuum opening system.

I use a DashLogic (plugged in obd2) to open n close it manually with the cruise control button. I monitor oil press, fuel pressure in the stock cluster too with it (manual 2013 didnt have oil press gauge).

Stock NPP/ electronic module open flats at 3500rpm+ when WOT. It is alway open when starting the car, which is not desirable for your neighbours when you have a solid roller cam chopping hard LOL.

10-02-2024, 05:41 PM	#1
sports car fan Drives: 2011 Camaro 2SS/RS Manual Join Date: Jun 2021 Location: eu Posts: 16	Question: Installation of GM Performance Z/28 exhaust, part no. 22906768 Hi, I am looking to upgrade to a dual mode exhaust system, while trying to stick to using original GM equipment. Even though they seem to be impossible to find any more. One option would be the Z/28 exhaust system, part no. 22906768. I believe this is a system with exhaust flaps. My question is if anyone knows how the flaps are actuated? If there is some kind of control mechanism / electronic control, how would these be controlled on my 2011 car, which I suppose was never intended to have an exhaust system with flaps installed? Another question is, would this exhaust system fit with the 1LE rear diffuser, part no. 22815277? And last, I have read a few times about an "NPP" exhaust system, part no. 22756148. Can anyone inform me what NPP stands for and what the difference is to the afore mentioned Z/28 system? Lastly, if anyone knows of anyone who has a set of the Z/28 exhaust lying around, it would be much appreciated! Thank you for any help!

10-02-2024, 06:43 PM	#2
Joe.G Drives: 2014 2SS/RS 6SP Ashen Grey Join Date: Aug 2021 Location: NY Posts: 1,707	I'll try to answer some of your questions, Z/28 exhaust is an NPP exhaust it is just a 1/4 inch bigger pipe size I believe. the 1LE Diffuser will work if it is for a NPP equipped model. As far as making the NPP Valve work there is a thread if you do a search. __________________ GM 3.91/TrueTrac OEM ZL1 Rims, 6 Piston Brakes & Side Skirts.ACST4 Splitter/Deflectors NPP M2W,GM Short Throw,GPI Ported Rod Mod,BO White PTB,CAI/JRE Scoop, GC Aluminum DS,Stainless Works Ceramic LTH/HiFlo Cats, Hotckis 1" Springs & Chassis Max Brace BMR Adjustable Swaybars,Trailing Arms, Adjustable Toe Rod, LCA & Z28 UCA Bushings Hendrix Solid Cradle Bushings Pedders Radius Rod Inserts Strut tower brace, Moroso Catch Can,SCT X4 Dynosteve,Remote Clutch reservoir,Hero Smoked Tail and 3rd Brake Light, Diode Dynamic SL1 Fog Lights AeroForce Dual gauge/Autometer pillar mount.

10-02-2024, 08:08 PM	#3
CamaroCracka Drives: 2010 Turbo LS3 Join Date: Dec 2009 Location: Palm Bay, FL Posts: 3,036	Z28s that get totaled get parted out and I don't imagine anyone is selling one off a running Z28 given their collectability. I just sold the mufflers off a 1LE NPP system and kept the rest of the exhaust for the future. Given you are in Europe, you will only want to ship the axle back portion. There is nothing special about it besides mufflers. The additional muffler opening is actuated by engine vacuum. You would also need a diffuser meant for quad tipped exhaust, i.e. not the one with big round openings. There are aftermarket companies that sell an NPP style muffler, but they are not OEM. __________________ 2010 SS - Kind of an On3 kit, CTR 78/80, CompCam 239/251 620/632 122+4, E85, Z28 suspension and ZL1 diff with Outlaw axles. Gen6 ZL1 brakes. 2011 Vert - 416/w 230/236 .612/.602 115lsa, 1LE suspension w/32mm rear bar. Z28 diff. Gen6 ZL1 brakes.

10-02-2024, 09:27 PM	#4
olblue75 Drives: 2010 2SS/RS Join Date: Dec 2009 Location: Clarksville Tennesse. Posts: 6,148	So I have a 2010 SS with a 1LE diffuser with a z28 exhaust system, so like others have said it’s a 2 3/4 system but the mufflers are the same as a ZL1/1LE 2 1/2 inch, the valves are vacuum operated. NPP is just a code like 1LE Z28 etc etc. Also I installed a C7 Corvette X replacing the Y portion of the exhaust sounds really good with headers and HF cats. Send me a PM an I’ll send you a sound clip. __________________ Orange Krush II 1LE Front sway bar, Splitter, shocks and struts, Z28 dual mode mufflers, Intake, UCA Bushings, and Toresen 3.91 Diff. 1 piece DSS Drive Shaft, ZL1/C7 Calipers, and 32mm JPSS Rear Bar. ASC race spec splitter and wicker. 6th Gen M017 Wheels. Stainless Works 1 7/8 LTs. DSE and PAFDT Suspension components.

10-02-2024, 09:42 PM	#5
Joe.G Drives: 2014 2SS/RS 6SP Ashen Grey Join Date: Aug 2021 Location: NY Posts: 1,707	Olblue did the sound change between the H and the X pipe? The system necks down at the mufflers? __________________ GM 3.91/TrueTrac OEM ZL1 Rims, 6 Piston Brakes & Side Skirts.ACST4 Splitter/Deflectors NPP M2W,GM Short Throw,GPI Ported Rod Mod,BO White PTB,CAI/JRE Scoop, GC Aluminum DS,Stainless Works Ceramic LTH/HiFlo Cats, Hotckis 1" Springs & Chassis Max Brace BMR Adjustable Swaybars,Trailing Arms, Adjustable Toe Rod, LCA & Z28 UCA Bushings Hendrix Solid Cradle Bushings Pedders Radius Rod Inserts Strut tower brace, Moroso Catch Can,SCT X4 Dynosteve,Remote Clutch reservoir,Hero Smoked Tail and 3rd Brake Light, Diode Dynamic SL1 Fog Lights AeroForce Dual gauge/Autometer pillar mount.

10-03-2024, 05:39 AM	#6
acutron42 Drives: 2013 Camaro 2SS AGM Join Date: Apr 2020 Location: WNY Posts: 935	Here is a link to the system I am installing. I was lucky to find a oem 1LE quad tip diffuser & set of ZL1 mufflers. With this setup, I will have control of the actuators with a switch. https://www.corvetteforum.com/forums...ne-intake.html __________________ 2013 2SS GPI built & tuned 415, spec'd by Andrew Cammer. GPI ported intake/tb/heads, Tooley springs, CHE trunnions, Callies rotating assembly, Diamond pistons, GPI SS3 VVT, ATI 10% ud damper, Circle D 3800, Kooks ceramic coated lt's with green cats, Mishimoto rad & oil cooler, Derale trans cooler, Holley efi rails. DSS driveshaft, trutrac with 3.91's, G-Force renegades, Hendrix solid cradle bushings Bmr: poly diff bushings, Strange adjustable coilovers, sub frame connectors, ZL1 npps, controlled with a vac pump & mac boost control solenoid.

10-03-2024, 03:11 PM	#7
sports car fan Drives: 2011 Camaro 2SS/RS Manual Join Date: Jun 2021 Location: eu Posts: 16	Wow, once again a lot of good information, thank you to everyone for replying! Yes, I guess I will have to look if I can find a second-hand system somewhere. Currently I have the GM Performance muffler 92206992 installed, which is the system with one tailpipe on each end, without the valves. I do like the sound - other than a horrible drone between 1200 and 2000 rpm - but I am hoping more can be extracted sound-wise with an alternative system.

10-09-2024, 11:36 AM	#8
WHAMMO Drives: 13' 1LE Join Date: Apr 2012 Location: Canada Posts: 2,653	I have a 1LE and the stock NPP catback is extremly potent, good to 650hp np. I wanted to upgrade to a full 3inch dual and not have too much of a bottle neck at the mufllers so I found Z28 mufflers on ebay or here, not sure. Got a crazy deal on em. I still have my stock NPP catback hanging on my garage wall, not for sale LOL. Z28 are 2.75'' and SS/1LE NPP are 2.5''. same vacuum opening system. I use a DashLogic (plugged in obd2) to open n close it manually with the cruise control button. I monitor oil press, fuel pressure in the stock cluster too with it (manual 2013 didnt have oil press gauge). Stock NPP/ electronic module open flats at 3500rpm+ when WOT. It is alway open when starting the car, which is not desirable for your neighbours when you have a solid roller cam chopping hard LOL. __________________ 13' 1LE Old setup: TSP 231-236/Tick 660/.105 PR, UDP, SW LT 2'' & HFC, stock NPP & H pipe, VR-DRX CAI, air scoop, Goertz1 manifold, 102mm BBK, 26" Toyo DRs, Forgestars R17x10 & F18x8, rear seat delete, remote Pat G tune Autocal, 7400 limiter, Spec Mini Twin. 91oct. 11.90@122.3, 0-60ft 2.0 / 11.99@123.6, 0-60ft 2.1 DA+819 ...519RWHP SAE Solid roller SBE LS3, FED, LLSR, 91oct, 605rwhp N/A. Tuned by Pat G. Build by me. Last edited by WHAMMO; 10-09-2024 at 11:55 AM.