Corvette Exhaust System Valves (NPP and AFM)

There are two very different valves for a stock Corvette C7 exhaust system. They are the NPP (nuclear propulsion valves) and AFM (active fuel management). In this video we will discuss what the valves are, where they are located and how they operate. Not all model Corvettes have both sets of valves. Leave questions and comments down below. Thank you for stopping by the Ozzstar's Cars channel.
-Glen (Ozz)
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[@SeanPennII]

I want you to know that when I was 18 I followed your video on how to replace the intake manifold gaskets on an LT1. And just last week at 24 I bought a 2016 stingray. Never thought I'd ever get a chance to own a c7. Thank you Ozz for your helpful videos.

[@ozzstars_cars]

That is awesome Sean! Congrats and enjoy your C7! Drive safely and thanks for the comment. It nice to know that my videos are helping people out. Take it easy. -Glen

[@frankiebpr]

This is what I call an explanation for dummies, which is a good thing!! Excelente demostración. Thanks Frank

[@ozzstars_cars]

👍

[@EBHERNANDEZ7]

I own a c7 2017 stingray. I'm just looking at youtube but learning a lot. Thanks for all the informative details.

[@lyzasacres7501]

Thanks for the explanation with visual aids! It was very educational and helpful to me. Superbly done!

[@ozzstars_cars]

I wanted to make sure everyone is clear on the subject. Glad the video was helpful!

[@davidmcclain5180]

Good information but for what it's worth, I have a 2019 Z06 manual trans and it doesn't have AFM valves. My friend has a 2016 Z06 Automatic and it doesn't have AFM valves either.

[@PRmercado]

That is also what I told him, I ha e a 2017 with NPP and no AFM. A 2014 with NPP and AFM. The 2017 was purchased new so I am the only owner. I just installed an AWE Xpipe and I looked again and no AFMs.

[@Goczku]

What do you think about corsa exhaust ? It is with NPP valves regular from remote controler. It will be good option ?

[@ozzstars_cars]

I think it's overpriced. Go with AWE kzbin.info/www/bejne/i5Kzg2OOpbGUrMk

[@Goczku]

@@ozzstars_cars thx bro💪

[@spelunkerd]

Wow, that's a topic I never learned, interesting.

[@ozzstars_cars]

Always something new, keeps us mechanical guys on our toes. 😀

[@robertgums4496]

I put a Range Technology plug in unit to disable the AFM/DFM system and have no check engine light. Just did a 3450 mile trip two weeks ago. No issues. By using this unit, I assume my AFM valve is always open which I guess would be freer flowing exhaust.

[@PRmercado]

I raised my vehicles, stingray 2014 has NPP and AFM, grand sport 2017 has NPP and I followed the muffler pipe and it did not have an AFM. Had several Guys look at it and no one saw it. Going to call the dealer and see what they tell me, thanks

[@GG-xs8vt]

So, I have my used (couple of months now) 2015 ZO6. Love it. I liked your diagram. I know I have the NPP valves because I can see them. How do I know if I have the AFM . Am I supposed to have both , NPP and AFM . Again new to all this. PS. I learned my launching from you tuber Robert McCready. What a blast.

[@josezarate3416]

Do you think it is a bad idea to straight pipe and muffler delete a bone stock 17 stingray? I don’t want a check engine light 😂 it does have npp and of course afm.

[@ozzstars_cars]

It will sound like crap and you will fail emissions with a check engine light

[@josezarate3416]

@@ozzstars_cars is there a way to avoid getting a check engine light? If I go this route… Im just exploring options right now. Thanks

[@ozzstars_cars]

@@josezarate3416 there sure is. 1) leave the stock exhaust alone or 2) install AFM valve simulators or reinstall them in the new exhaust or there will be a check engine light

[@HowtoAutomotive]

Great Scott do you get 1.1 giga watts with the Nuclear propulsion valve

[@ozzstars_cars]

Close, 1.2gw 🤣🤣🤣 Sucks we won't be hanging out next week for our annual SEMA event, hopefully next year.

[@HowtoAutomotive]

@@ozzstars_cars it does suck but the story will be twice is good!

[@najibullahnazari5813]

I have q Question I have the C7 stingray and I only has the AFM Valves , I bought the Borla Atack exhaust and X Pipe when I installed them the Borla Atack has only the NPP Valves which is located at the exhaust tip and I took the AFN Valves and transfer them to where NPP Valves are located but the wire was not reaching the NPP because it was too short so I did not plague them and after finishing the the installation I start the car but check engine light came on , so Do I have to connect the AFM Valve plugs to Npp where it located at tips of exhaust if I do that then I have to add wire to existing plugs in order to reach the NPP Valves location . so If do that the check engine will be eliminated or what do you recommend, thank you

[@ozzstars_cars]

You either have to buy the correct pipes with AFM or bypass the AFM valves.

[@davidraduziner8732]

IS THERE SOME MODULE DEVICE YOU CAN PLUG IN THE AFM OR NPP TO DEFEAT THIS FEATURE IN ANY MODE ? SO THIER ALWAYS OPEN? ALL 4 PIPES IN ANY MODE? THX SIR

[@PRmercado]

Great video put not all corvettes have a AFM, I can send you a link of at least three videos, when they remove the rear mufflers you do not see any AFM. And if you go to Corsa they have different options with NPP and AFM, with just NPP and with no NPP or AFM. Watch this video: kzbin.info/www/bejne/paG5mYB6l9KnZq8 you can see that when the mufflers is removed there is no AFM. I am just trying to understand, guess I will have to get under the car before I buy my exhaust, corsa has different options I would think for a reason. Thanks

[@ozzstars_cars]

Those mufflers he removed in that video are not oem from what I saw.

[@alibongo6414]

How can I fix my parking brake cable ? I removed it, can you do a video on how to fix it, it’s a c7 corvette stingray

[@ozzstars_cars]

What do you mean fix it? What is the problem?

[@scottbarker9058]

1 quest,,,ozzstars cars.....i plugged in a component uner my dashboard thr keeps the V_4 MODE from ever comming on......lots of literature says the lifters are stressed with it goen back n forth...so my 10 z06 with the manuel transm...never goes in2 v4 mode,,no check engine lights-etc,,,wonderful......so that means that the AFM valves are always open..correct..like they are not even there????

[@ozzstars_cars]

That's correct. AFM valves are open.

[@richardhilliard5558]

As a new C7 owner, I really appreciate videos like this. Great job explaining NPP and AFM. The question I have is: Do the aftermarket exhaust systems from companies like Borla and Corsa eliminate the NPP and AFM?

[@ozzstars_cars]

Keep that in mind when pricing because there are different configurations.

[@jrparker4804]

I just got a 2016 C7 Stingray with AFM and NPP exhaust valves. I pulled exhaust fuse 42 and plugged in an AFM bypass into the OBD2 port I got from Range Technology. No more V4 or valve closing. I didn’t get a Corvette so it could sound whisper quiet or for fuel economy. AFM was a GM debacle with lifter issues out the wazoo. Back pressure? Stop it. My next move is a muffler delete. Buying aftermarket expensive exhausts is not necessary.

[@scottbarker9058]

@@jrparker4804 im getten mine deleted as well.

[@corvette412]

Does your Grand Sport have an AFM valve? I understand that from 2017 on, the z51 and grand sport with a manual transmission does not have the AFM valves. Tadge Juecter explained this is a corvette forum response.

[@ozzstars_cars]

Yes my Grand Sport has AFM, they all do.

[@wyattoneable]

A very good explanation. On another note. Take a look at the past chatter on our common chat area. Eric is having some fun at our expense. But it's all good and kind of funny.

[@ozzstars_cars]

I saw it. He fly's a 🏳️‍🌈 flag so it's the pot calling the kettle black. haha

[@MultiVette85]

A great presentation and it should explain it very well, thank you.

[@ozzstars_cars]

Thanks

[@RustyGlovebox]

Exhaust systems have come a long way from adding a couple of Cherry Bombs...lol

[@ozzstars_cars]

Oh yeah, the good old days!

[@breadn5556]

I can confirm C7 Stingray 1LT with the NPP option.

[@ozzstars_cars]

The truth be told!

[@DanDurant-ti8pb]

I realize this is an old thread. If I have a stock C8 with stock exhaust and If installed npp exhaust that someone had from the factory npp would it work on my car? I realize I would have no way to open and close them? I wonder if they would work if I left them open all the time?

[@ozzstars_cars]

I separate circuit would need to be installed to control the valves. That would be slick!

[@normvernon1446]

My bone stock 2019 zo6 with auto does not have AFM - just for reference

[@ozzstars_cars]

Lmao, yeah okay. 🤣

[@johannesvanhoek9080]

Thanks once again, I have a 2019 GrandSport and learning as I go

[@ozzstars_cars]

👍

[@SERGE_Tech]

dude i love your talking into the camera vlog style great info as well. thx!

[@ozzstars_cars]

Thanks Serge!

[@redmanrm1]

I have 6 codes from installing non npp on npp car

[@ozzstars_cars]

Yup, it's common.

[@dirkpalmer1067]

Very educational, thx!

[@ozzstars_cars]

Glad.the video was helpful!

[@LinusScrubTips]

It’s not actually back pressure but exhaust vacuum. If you run too big of an exhaust you don’t get enough vacuum which reduces efficiency. Think of exhaust gas as little balls rather than a water pipe. Each “ball” leaves a vacuum behind it which helps pull exhaust from the cylinder on the exhaust stroke.

[@Steveleanr]

Do you like the AWE exhaust? I'm contemplating it for my C7 Z51.. very informative videos!!!

[@ozzstars_cars]

I thought it was well made and sounds great and no annkying highway droning The owner says he really likes it.

[@stikupartist3698]

Did you get it? I put one on my 2016 z51 and love the sound.

[@petelanzone484]

FYI on my C6Z06 I have those valves as well however not identified on the sticker or the build sheet as "NPP". I also see the fuse is there as well which is labeled something like "exhaust Management" or something like that.

[@sebasbecerra1435]

So what if you do an exhaust setup that doesnt have AFM valves and you unbolt all 4 but mix em up? How do you determine which 2 are AFM are all the actuators the same or no?

[@ozzstars_cars]

NPP valves look completely different than AFM valves. Check this out kzbin.info/www/bejne/gX2QdX1qrMZoi5I

[@sebasbecerra1435]

@@ozzstars_cars ok so now I know which is which but the little black actuators I unplugged all 4 then unbolted them from the stock exhaust so I now have 4 of the black actuators and I dont know what is what because they all look the same, I just need to plug in the AFM actuators to get rid of my cell I hope Im not confusing anyone?

[@nathanmoore968]

New to Vettes, great info! Thanks a bunch.

[@ozzstars_cars]

You're welcome

[@indyme2]

Taking one for the YT Garage Gang, lol. Great video. Miss my 66 Vette.

[@ozzstars_cars]

I would miss it to. I don't have the heart to sell my '93 Corvette.

[@trobertson1825]

If you have a manual you don't have that worry Z51

[@ozzstars_cars]

Don't have what worry?

[@SteveRobReviews]

HAHAHA it did fog up your lens big time. I had no idea this even existed. Good stuff Glen I'm just enough of a car guy to find this quite interesting. Cheers

[@ozzstars_cars]

I believe you are a man with lots of wisdom and knowledge and knew this all along. 😁

[@thundarwabbit5140]

Thank God for you and the explanation. Really appreciate the in depth detail.

[@ozzstars_cars]

You are welcome Thundar, glad the video was helpful.

[@thomaslapointe4671]

Great Video & Content, How can I control NPP Valves through Vaccum ? My 416 Stroker (LS7 Crank & Ti Rods) w LS7 Manifold, Flange Cat Section (want a Stealth Mode for 96 Land Cruiser Swap Ultimate Hunting Vehicle

[@ozzstars_cars]

They are electronic solenoids, Vacuum won't work.

[@royo9898]

To clear but manual don’t have dod to switch to 4 cylinders so what is for afm in manual c7 ?

[@ozzstars_cars]

I have no idea what you are asking.

[@royo9898]

@@ozzstars_cars Excuse me, my English is not good enough, but I have a C7 manual 2015 there is no DOD (displacement on demand) in c7 manual Why does my car have AFM system ? as we know DOD to stop 4 pistons in ECO mode and AFM related to DOD

[@chase141c]

GREAT VIDEO!!! I’m new to the corvette world (6 months) I have a 17 GS 7M. I have NPP and AFM. I use afm all the time when I’m on the highway in 7th gear. I can hear, feel, and see (V8 to V4 on the dash) when it switches back and forth. I was thinking about getting a Corsa set up. Which setup should I get to keep the AFM AND NPP. Ohh and doin need a special x or h pipe for that set up. Are there any other options to keep both activated? LOVE YOUR VIDEOS!!!!!!

[@ozzstars_cars]

Your C7 already has an OEM X pipe, with required catalytic converters. I would suggest the AWE exhaust which is well made and sounds great. You will need the model pipes with both AFM and NPP valves, otherwise you'll have a check engine light on. Thanks for watching the videos Chase!

[@hilarykerns9340]

Explained quite well, keep the great videos coming, thanks.

[@ozzstars_cars]

Thanks for your comment

[@nallen6559]

Excellent explanation, concern was AFN on mine, so many choices it's somewhat confusing. Have a 2019 Stingray and want to run Borla S-type non-NPP, will look for the AFM valves and order correct exhaust.

[@ozzstars_cars]

The quality of a Borla exhaust has never impressed me. I believe it is overpriced for what it is. Have you checked out the video I posted on an AWE exhaust system for a C7?

[@robertcarmody2312]

Not all C7 corvettes have AFM valves. My 2019 Grand Sport was built with NPP and no AFM valves. As a matter of fact many 2017-2019 C7s don’t. This pertains to M7 GS, Z06, and ZR1s.

[@ozzstars_cars]

😂😂😂

[@CarsExposed]

Nice explanation Glen I also have an exhaust flap on my Renault Megane 4 pot 1.5 turbo diesel for some reason it doesn’t sound as good as your vet 😊😁👍👍👍

[@ozzstars_cars]

1.5L Igor? I have one of those in my riding lawn mower. lol

[@CarsExposed]

@@ozzstars_cars 🤣🤣🤣🤣 I thought so 😜👍

[@knjpollard]

I have an C7,A8 Z06, but fortunately disabled AFM with my Diablo tuner. I do like the NPP because tour mode sound is great for trips. When i want sport sound I switch modes. If I get an after market exhaust it must have NPP.

[@ozzstars_cars]

Did you know that the exhaust settings in the center screen can be adjusted?. For example Sport sound while driving in tour mide

[@CFurnace-72]

Hi Glen, Just got a 14 C7 z51. Love it and immersing myself in all its technology. ? though; Does running in eco or 4 cylinder mode cause more engine stress and lessen engine life?

[@ozzstars_cars]

I wouldn't say it causes more stress or necessarily causes shorter engine life. There is a small possibility of valve lifter issues but it is rarely happens on the C7 if the oil is changed at regular intevals like 4.5k miles or less. Putting an automatic transmission in manual mode and using the paddle shifter avoids AFM all together. My personal C7 is driven that way 95% of the time. Btw, V4 mode will also occur in tour and sport mode. Enjoy your car Matt!

[@davidvargas6080]

Great video! Where can I get a build sheet?

[@ozzstars_cars]

Contact the NCM in Bowling Green Kentucky. The National Corvette Museum sells copies.

[@jlacson74]

Wow. I learned something new today about my C7 Z51. Thanks for the vid.

[@ozzstars_cars]

Good news!

[@SmittySmithsonite]

Your car spit at us, Glen! That's not very nice ... 😁 Wow, crazy - more acronyms I'll get confused now! Wonder how long all those valves would last if you drove those cars every winter? I'd bet not very long. Great explanation though, Glen - I'm much less confused now! 🤣 Oh, and the Mustang stole this idea. My buddy had an '18 GT for a while - one of my very first videos of when we did the resonator delete. Has the flapper valves at the tips. That's the loudest factory system I've ever heard. All adjustable in the cluster. Suspension adjusts there too! With a factory line lock! Impressive. Was never much of a Mustang guy, but that was one well thought out car. Aside from the plastic oil pan and Briggs & Stratton -looking drain plug.

[@ozzstars_cars]

I have some really cool video of a cutaway display Mustang that I saw at SEMA 2019 a year ago, I believe it's a 2019 Shelby 350. The car was mounted sideways on a rotisserie. I was really turned off by all the plastic I saw underneath. It's the sign of the times I guess. My '18 Grand Sport doesn't have a factory line lock but it does have an optional launch control when it's in the track mode setting. That will put a smile on your face for sure when you feel the positive G forces! Btw, that was a good observation now that you know my car is a spitter but I still love her anyway. haha Take care buddy.

[@SmittySmithsonite]

Ozzstar's Cars - Nice, I’ll have to check that out. Yeah plastic everything these days. Waiting for GM to use plastic pistons on the new Silverado’s LOL! They might as well the way they are building them today! That launch control sounds like a blast! That’s one part of technology I don’t mind. 😎 Enjoy your weekend, Glen!

[@juvisanchez]

Thanks for the explanation, I was going nuts trying to figure out the lingo. People at the dealership didn’t know what NPP stands for.

[@ozzstars_cars]

Hopefully you shared the video so they know now. 😉

[@ianbrown9447]

Awesome! Just bought a 2018 Z51. This is great info, thank you.

[@ozzstars_cars]

Glad it was helpful Ian

[@PRmercado]

Try this other video : kzbin.info/www/bejne/gJfWq55pYs-Wq9U

[@bugmoto]

2017 Grand Sport manuals (and possibly Sting Ray manuals) with NPP do not have AFM exhaust valves. The cars have the AFM programs and engine components but not the valves in the exhaust system just in front of the mufflers. The automatics still have the AFM exhaust valves.

[@ozzstars_cars]

🤣🤣🤣

[@bugmoto]

That info comes directly from Tadge Juechter - Corvette Chief Engineer.

[@monicashookman3305]

My son just took off the muffler system on his c6 to replace with new ones! So I’m sending him this video to learn about it! Thank you! I subscribed to you being a mom I can now understand what’s what thx

[@ozzstars_cars]

You're a cool mom! You'll hear his car coming and going with those new mufflers. 😄

[@dennisryan7568]

Exceptional video and explanation - much thanks !!!

[@ozzstars_cars]

Glad it was helpful Dennis! Thanks -Glen

[@julianmartinez6658]

Thank you. First video I've seen that really explains the NPP AFM exhaust. I have a 2014 Stingray and with your help, I found out I do not have the NPP exhaust. Thanks

[@ozzstars_cars]

Awesome news Julian! Exactly why I made the video because there is way too much misinformation and gossip out there in cyberspace. I wanted to set the record straight. 👍

[@Goczku]

Why not ? NPP let you set your valves

[@monicashookman3305]

Thx again! So I was so excited to discuss to be able to have shop talk with my son yesterday about his exhaust plan! I knew what he had , what he still needed and he was shocked lol!! Can’t wait to check out another corvette related video! This made me feel more safe about what he’s doing! He’s only 20 yrs old that cars fast so my mind can get carried away ! Not now I was informed sir and I worried about nothing!! Thx again

[@ozzstars_cars]

Good news. You're welcome Hopefully your son shows strong maturity and responsibility driving a car that powerful.

[@chrissimon8403]

Glen, us lefty techs prevail, great explanations!! Unfortunately it's time to put the Beasts to sleep for the winter.

[@ozzstars_cars]

Yeah winter is no fun for sports car driving. Thank you Chris for your comment. 👍

[@tonypartridge7085]

Never knew what NPP meant! Thank you!!!

[@ozzstars_cars]

You're welcome Tony. Now you know. 😉

[@CubasAutomotive]

Very nice video. Lots of good info here 😁👍🏻👍🏻

[@ozzstars_cars]

Thanks Cuba 👍

[@bmm7119]

Excellent video and explanations!!

[@ozzstars_cars]

Thanks!

[@LayneSteighlee]

is there a way to disable the AFM valves? I have my NPP fuse pulled.

[@ozzstars_cars]

There sure is.

[@jrparker4804]

Of course, buy a Range Technology AFM bypass that is plug and play…plugs into the OBD2 port. Costs around $200. I have it and NO MORE V4 mode! Also pulled fuse 42 so no more NPP valve closing.

[@scottbarker9058]

such good info...thanks!!!!

[@ozzstars_cars]

You're welcome Scott

[@chrissimon8403]

Glen I was reading that after a certain RPM the vaves close hence the reaso why people are putting the mild to wild on Is that correct?

[@ozzstars_cars]

The AFM valves have to adjust when the engine goes into V4 mode to control back pressure but the quiet sound really isn't an issue on the highway for me. Have you seen the vid I posted on the AWE exhaust install? If you want a more aggressive sound and no drone check it out. Ozzstar approved. lol Take care Chris.

[@chrissimon8403]

@@ozzstars_cars Thanks Glen I'll have a boo.

[@ozzstars_cars]

@@chrissimon8403aftermarket C7 exhaust vid: kzbin.info/www/bejne/i5Kzg2OOpbGUrMk

[@jemagee83777]

Best explanation and demonstration I've ever seen thanks.

[@ozzstars_cars]

I appreciate the kind words jema.

[@wtbm123]

Cool

[@ozzstars_cars]

👍

[@user-fq9ug8zl6n]

Very good video. Learned a lot

[@ozzstars_cars]

Good news

[@trobertson1825]

Glad I ordered a manual

[@ozzstars_cars]

That's always helpful. Where did you buy it from?

[@theonethatruns]

Solid info boss thank you 👍

[@ozzstars_cars]

Sure thing Sharky, you're welcome.

[@kengillespie3897]

The manual transmission C7 Z06 does NOT have AFM valves.

[@ozzstars_cars]

Are you sure about that? Better check a few different model years.😉

[@kengillespie3897]

@@ozzstars_cars I am most definitely sure about the manual transmission C7 Z06 NOT having AFM valves. I noticed another person posted that their manual transmission C7 Z06 does NOT have AFM valves.

[@ozzstars_cars]

@@kengillespie3897 and then there are the Z06's that do. Some folks don't know where to look. 🤷‍♂️

[@kengillespie3897]

their@@ozzstars_cars I am only stating that the manual transmission C7 Z06 does NOT have AFM valves. Same thing another poster here stated about their vehicle.

[@rickjones2985]

Pretty cool video man !

[@ozzstars_cars]

Thanks Rick

[@rickfuentez8797]

great info,always nice to learn something

[@ozzstars_cars]

Glad you enjoyed it. Take care -Glen

[@stingk5295]

Great Detail, Very nicely Done.

[@ozzstars_cars]

Thank you Sting.

[@kengillespie3897]

Here is an excerpt from Ask Tadge on CF: "For 2017, we have eliminated the valve on Z51 and Grand Sport (manual transmissions only). Manuals still have AFM, but the torque levels are low relative to the automatic so the N&V issues are manageable without it. Also, the AFM only works in Eco mode, so it is easy to avoid if you want to."

[@jemagee83777]

That's why manual transmissions still RULE.

[@ganoog]

Thanks 👍

[@ozzstars_cars]

You got it!

[@budcarr8673]

Great video !

[@ozzstars_cars]

Thank you Bud!

[@dateatorjr9671]

Drawing time with Glen! ✍🏻. I was really surprised to find out that the base Stingrays have no rear sway bar! What fun projects do you have coming up for the GS?

[@ozzstars_cars]

Yes the rear sway bar delete option surprised me too. For the GS I will soon be installing a stage 2 front splitter.👍 Hope to install it soon. Thanks.

[@shaark92]

so during V4, the valves are closed. doesn't that mean there is (some) compression in that "dead" cylinder? great work on the Vid. I better understand the difference in AFM valves and NPP. I gather the AFM valves reduce the cross section/effective diameter of the exhaust pipe upstream of the muffler. NPP is driven by the ECM mode? ECO is the only one which closes the NPP valves?