Nithros

Has anyone opened up the C7Z stock muffler (cans) and blocked off the internal pipe holes and removed the packing like some of us did on the C6Z?

Theta

I have scoped the NPP exhaust for the C7, and there is no packing - simply perf holes for re-route and resonation chambers.

I'd cut one of these extra ones open, but someone can put it to good use since it's still new. Once we have someone wind up with a wrecked one, we can have the full inside pics rather than just endoscope pics.

I'm happy to post those if you'd like.

Randy WS6

Wonder what 4 outlets would sound compared to the NPP 2 outer outlets

Theta

The perf holes run the entire length of the inner pipe. By blocking those, you eliminate that pipe entirely.

So, it wouldn't really be 4 outlets at all unless you cut the inner pipe, which changes the length and resonant frequency inside the muffler. Might be great, might be horrible.

MikeLsx

It would be great to be able to block off the perf holes( on NPP and non NPP). Then when opened in track mode(on npp) the exhaust would be NEAR muffler delete loud, but then when closed it calms down.

Theta

I think visuals would help here...

If you blocked the perf holes, there is no more bi-modal exhaust. You'd have a straight pipe with an actuator, which when closed will act as a proverbial potato in the tailpipe.

No matter which pipe's holes you block, you still cause this situation. The larger holes on the main pipe allow the flow/waves to travel into the can/shell and bypass to the secondary tube. That secondary tube has smaller holes to attenuate the sound and alter the flow of the exhaust gases.

Block the large one, and you have the situation described above - a straight pipe with an actuator. Block the small one, and you have a pipe with a resonation chamber and an actuator.

Both end in disaster.

tblu92

I think that route is a waste of time with minimal positive results--
Either buy a catback system that has both sides open all the time OR so like many of have done---simply eliminate both mufflers and intall the dual 4" flowmaster dual wall tips--Just barely louder that NPP exhaust with the one side open---no resonance-- no drone and all can be done for about $150--Sounds awesome at WOT around town mello
This car with 4 cats is actually quite tame without mufflers at all--at P/T
PLUS you save off over 50lbs of weight off the rear

Nithros

[QUOTE=Theta;1589669703]I think visuals would help here...
QUOTE]

Yeah it probably would because you have no idea what I am asking about. I had some from my C6Z but probably could not produce them. This is not about defeating the NPP. On the C6Z - inside the muffler can, the straight through pipe is perforated and the can is packed with some kind of fiberglass sound deadening material, the mod was to remove the material and close off the perforations so basically it was a straight through pipe. I think someone has already posted that there is no packing material in the C7 cans. Hope this helps.

Nithros

On the C6 it sounded way better. I was just a question. Some people enjoy doing free mods in their garage just for the fun of it. If I understood your post correctly (and I may not have) - although I do like what you said about the weight savings and like it loud, some people would rather be able to turn off the noise from time to time (like not bothering the neighbors when you get up at 5am for a Tail of the Dragon run). That's a nice feature.

Theta

Edit: ...Cleared up below by Ed, no veggies in the tailpipe.

Sorry, Nithros.

Old Yellow

Here's a link to the C6 muffler mod the OP was talking about.

On the C6 NPP mufflers there was a resonance chamber at each end. It didn't require the exhaust to flow through the perforations to get to the other outlet. However by closing off the perforations the NPP side became a true straight pipe without any turbulence. The result was a louder exhaust note with the NPP valves open. When the valves were closed you had normal quiet exhaust sound. It was/is a very popular mod for C6 NPP cars to make them a little louder for 0 dollars, and a lot of effort.

The pictures in the thread don't show the resonance chamber because you opened the can only where the perforated pipe was.

I hope this clears up the misunderstanding as I do believe the C7 muffler has similar resonance chambers. I have never seen a muffler that required full exhaust flow through the perforated pipe. They are mainly used to absorb pressure pulses.

https://www.corvetteforum.com/forums...eo-inside.html

Ed

Theta

Thank you, Ed!

I was banging my head against the keyboard for half an hour before writing that reply wondering what in the heck I was missing here.

This is nearly the opposite end of the spectrum from what I thought the OP was suggesting. I have to admit that I have precious little C6 insight, so that's my fault for assuming.

I actually came out here with a borescope and made a decently-long video that I was getting ready to upload to show why what I was saying was correct, but we were, indeed, talking about two different things. My bad, Nithros!

My thoughts were simply on flow, not resonance. Makes a hell of a lot more sense - otherwise, as I had argued, you'd have a proverbial veggie in the tailpipe!

Hell, if it wasn't going to help someone down the road when it gets sold, I would have cut open a C7 muffler right here to show it off.

Edit: From simple measurements, it would appear that the chambers would have to be significantly smaller on the C7 mufflers based solely on the start/stop of the perfs, and the end of the secondary res tube. It's funny that in 18 months, none of us has cut one open.

imxz28

I'm still searching and here's my original thread on the subject

https://www.corvetteforum.com/forums...-cut-away.html

Theta

Yep, and that routing information was given to me by a very reliable source quite a ways back. Obviously the picture is stock art, but the chamber does supposedly run all the way back (again, from what I was told. I (and another member here) have taken measurements, and if there is a resonance chamber, it would have to be pretty small.

Herein lied the problem with my argument - he was talking about a C6 NPP muffler, and I was focused on (what we think to be a correct representation of) a C7 NPP muffler.

After about 3 minutes of looking at the C6 muffler, the benefits of the mod became clear (if not a bit difficult for DIY sans-welder).

Bill Dearborn

The C6 ZR1 mufflers didn't have the perforated pipe in the straight through mode and those mufflers became standard on the Z06 in 2010 or 2011. That eliminated the need for the mod. The mod made the mufflers sound louder in straight through mode but it didn't do anything for performance.

Bill

mittens

So Bumping this thread.... last post was 2 years and 3 months ago..


has ANYONE cut open a NPP to see if you can do the old C6 muffler Mod to a C7?

madrob2020

In search thread box type in:remove C7 muffler packing material-you will see anatomy of C7 Z06 muffler. Has pics.

mittens

So I do that and can find both the c6z muffler cut out threads npp stuff which I have done to 2 other cars. And also a long thread in the c6 stock muffler.

If you see a thread for the inside of a c7 muffer could you please post a link to it? I am not finding one at all

madrob2020

Sorry, I've not figured out how to link past threads. Type in "remove C7 muffler packing material" in the thread search box. About 4th one down by "Privateeye007" dated 4-28-2017. Its for the C7 Z06 & shows how the inner can(s) are divided into 2 separated chambers with a BUNCH of material. This was while viewing C7 Z06 forum but don't know if that makes a difference versus "plain C7 forums".

mountainears

Here's the thread I think.
https://www.corvetteforum.com/forums...t-muffler.html