I Just want to start out by saying I already have the NPP exhaust fuse pulled so the baffolds stay open all the time, and I absolutely love the sound. I would be ok with keeping it like this. I am just wondering if there are any quick, legal ways to make the exhaust even louder than it already is (which is pretty loud)
1 – put an x-pipe on. Either the Borla or Corsa double helix. It will make it a little louder and change the sound some. I did it, liked it, but not enough for me. I would do it again. A step in an overall exhaust build out process and reasonable.
2 – Do a muffler delete. I have not done this on the Stingray. Others have done it here on the forum. Not my recommendations due to drone but others are very supportive. Recommend doing research on sound / drone. I’ve done it other cars and the volume / drone was too much for me; IMHO. You cut the mufflers out and put in straight pipes and a set of tips. If you have NPP, you will need to zip tie the NPP valve actuators off to the side under the car to avoid throwing a check code.
3 – Aftermarket mufflers. With NPP, you need to decide if you want to maintain NPP functionality or not. That will significantly reduce your available selection if you want to keep NPP; supported by primarily BillyBoat Fusion and Borla dual mode (like Atak) systems only. If you don’t care about NPP support, you have all kinds of additional, cheaper options, in systems. If you go non NPP support route, you will need to zip tie the NPP valve actuators off to the side under the car to avoid throwing a check code. Second, maintain AFM functionality or not; there is more support for AFM (valve back) options. If you decide on a system that does not support the AFM valves, like NPP, you would need to zip tie those actuators off to the side also.
I went Borla dual mode Atak mufflers and combined up with the Corsa double helix x-pipe. The Borla (as well as BillyBoat Fusion) support AFM and NPP both.
4 – headers and a tune. There are long tube, shorties, catted,and non-catted options. However, even with shortie and cats, you will “most likely” need to also put a tune in to eliminate the probability of a check engine error light being thrown due to the location or non-existence of the cats that are monitored. Sound volume is reported to be much louder with this change even with the remainder of the stock exhaust in place, between the headers and tune you get a bigger bump in performance…
Another optional solution from one senior technician:
You don’t have to pull any fuse, if you go into the radio and set your driving preferences you can leave the valves open all the time.
As far making the car sound louder and really mean, install a set of headers on it. Our C7 has an awesome growl to it.
Headers replace the exhaust manifolds.
My car is a 14. I tested it yesterday the valves never closed, about the NPP valve.
I have a GM MDI diagnostic tool hooked up and there is no open or closure of the valves. Also if you unplug your NPP valves it does set a code for that. I have not been able to figure out when it activates the MIL light though. He code pops up immediately but it does not request the light. Mine light has gone off but was not logging when or what caused it to set the mil for the NPP valves. I have a customer who is also bringing his car in where he went with and exhaust system that removed the NPP and now he has thrown the mil light as well.