I have a base 2LT C8 with the regular exhaust. If I had a performance exhaust without the valves, will it just always be loud? Will I have a check engine light? Can I even do that?

 

Same situation here. My delving suggests the following: 1.) Yes, it will always be in 'Track' mode; 2.) No, it will not throw codes; and 3.) Yes, it is possible. I've been tempted, esp. considering the healthy number of used Performance Exhaust systems, as alot of guys go z51 and then want to got with an even hotter system. I rather like the classic GT aspect of my car. In fact, that's what I intended it for. In that light, an enthusiastic exhaust note wasn't so important to me. That said, and in retrospect, I've got to say that a little more snarl would better match the feel of the car quite alot of the time. My plan is to see if I can get a local guy to let me drive his z51 (or an SR w/perf exhaust) set in track exhaust mode, and see what I think. My hope/prediction is that I'll like it quite a bit. From what I've been able to discern, even in Track Mode, the exhaust, under highway/GT conditions, is not too loud, but will growl when prodded.

 

Great question. Hopefully you get good answers here shortly from members. In the meantime, my opinion is that you wouldn't get a check engine light and that would only come on if you alter or remove the catalytic converters. I could be wrong though. I would look into possibly modifying or adding the OEM factory performance exhaust so that you don't have to worry but it's your call.

 

I am assuming, in the following that by "Performance Exhaust" you mean replacing the the non NPP exhaust with an NPP exhaust system. The answer is different if you meant you want to replace it with an aftermarket system that has no valves in the exhaust system. I see the "no valves" statement in your question, but does that mean no valves in the exhaust system, or no valve actuators for the Tailpipe Exhaust Flow Control Valves in the car?

Yes you can change it out.

Your non-NPP exhaust does have the Cylinder Deactivation Exhaust Flow Control Valves. You will remove your existing actuators for those valves and attach them to the new exhaust. The new "Performance Exahust" will also have the Tailpipe Exhaust Flow Control Valves - and you will not have actuators for those. Folks that have done this report that default position of the those valves without the actuator present is open. And yes, it will be louder.

Its possible that you will get a CEL but if so, that can be corrected with a re-learn. Any time that the actuators are disturbed, or removed and re-installed on a different exhaust system, there is a possibility of that.

It the question was about installing an aftermarket exhaust with no valves in the exhaust system- you will need a simulators attached to the harness where the existing Cylinder Deactivation Exhaust Flow Control Valve actuators are attached to prevent the CEL. It will be louder too.

 

Spend money on high flow CATs (if you can where you live) vs cat back exhaust. You will get more bang for your buck in terms of performance and sound. Unless you plan on a tune and or forced induction. There is no real need to replace OEM exhaust. It’s the CAT that restricts the flow the most.

 

If anyone wants a NPP exhaust, I still have mine from my 2021 SR in my attic that has about 800 miles on it. Free to anyone that wants to pick it up in SoCal.

That is all….

 

I wanted to go that route too but it appears that lots of CELs happen and there is a high probability that GM may not warranty your car. I believe cat back is a safer route in terms of warranty coverage and less hassle with CELs. I just don’t know if I want to throw money and time into something that could potentially be a hassle later on.

I did do Random Technology high flow cats on my C5 Z06 with LG Motorsports port matched headers and stock titanium exhaust. It was a beast. The cats are no longer made and I think Random Tech is out of business. Is there an equivalent to Random Tech cats for the C8? Since the C8 has all this new tech, I am a little more apprehensive about headers and catalytic converters.

I agree that cat replacement does give you best performance for the buck; albeit, with the caveats I mentioned above.

 

…I can say from experience that installing an NPP exhaust on a non-NPP C8 is an outstanding upgrade! Yes, it’s open all the time. No, it doesn’t throw any codes. No, it isn’t annoying and has no drone. I got one for free from a member here. Did my own install, so all it cost me was a Saturday of my time…transfer the AFM, don’t worry about having the NPP valves, and you’ll be good to go!

 

What exhaust did you end up with?

 

…how my NPP exhaust sounds in non-NPP car at start-up…

 

An OEM NPP exhaust.


NPP & non-NPP exhaust side by side. NPP is the one with the valves right before exhaust tips (top of the pic)

 

Yes, it will be always loud. You might get a CEL for the V4 MFD valves, I think all exhausts have those.

 

This is mine, swapped in a NPP exhaust. It's quiet in the cabin. No codes ever. I kept the AFM valves. Only thing I can add is an electric ratchet help getting the 10mm bolt out on passenger side.

 

Oh, and the worst part of the project is getting the bumper off. This video shows how it's done.