Lotsokids

For the last couple days, I've been reading about drilling a 3/4 or 1 inch hole into the stock muffler to get better sound.
Not much info about the NPP muffler, except where you cut it open and clamp the center baffle holes closed (picture below). There are 2 outlet pipes, so I guess drilling the holes does not apply, because of the different flow routing?

Question: If you cover the holes with the clamps, does this just make it basically a straight-pipe? What's the difference between this procedure and a straight-pipe?
I wish I could find a picture of a complete NPP muffler cutaway to see the flow through the chambers.

mittens

the difference is you have the quite side to switch to, and the strait side when open.

BigBlok502

The NPP does not need the modification you are referring to, its pipe is not perforated and with the baffles open it effectively is a straight pipe. The muffler you have pictured is a Bi-Mode for the early Z06, works just like the NPP but has 3" over axle pipe whereas the NPP is 2 1/2" over axle. Here's a picture of an unmodified early Z06 Bi-Mode.

mittens

from what I remember the ZR1 was the first to basicly be modded form factory with solid pipe, and then some later modle c6zs got it, but the NPP had holes.... BUT I also have enver owned a Car with NPP and cut one open I have done the mod to 3 Z06s.

Lotsokids

Well, my current NPP system is OK (with fuse pulled to remain open), but I'd like it a little louder. For me personally, I need to find that perfect balance of loud exhuast without drone on the highway.
I wish I had a lift at home. I would like to try to "make" a system similar to this. It doesn't seem like it would be difficult. I understand the worst part is removing the stock exhaust.

mittens

here is a video of a before and after on the second one I did. car was a 2007 Z06, 431 LS7, medium to smaller cam, long tubes, off road X, and factory mufflers. with them closed its stock quite... open its nice and loud..and talking to people in parking lots.

JimmyS5600

Lotsokids what is the exhaust set up you posted? I too have NPP and it doesn't do it for me either

saplumr

If you want a truly adjustable volume cutouts is the only way to achieve it.

Lotsokids

I saw it on Ebay:
https://www.ebay.com/itm/05-08-C6-Co...W/153142222709

There is a cheaper black setup, but the seller's feedback isn't great:
https://www.ebay.com/itm/Maximizer-C...h/171977561986