NC Emissions Tests and Long Tube Headers

[Vanthios]

I currently have a 2015 RS and am considering moving up to a 2015 or 2016 SS. I've been longing for that beautiful V8 sound for years and would really like to make it sound the best I can. For starters I'd like to drop in some Kooks Long Tube headers. Paired with the NPP exhaust the SS sounds amazing. However, from what I've heard (in person and in YouTube videos), the catted headers don't make as mean a sound as the catless headers; moreover, there's a pretty noticeable difference.

So I got to thinking... If a major concern with catless headers is coming across some trouble in emissions testing, why not just switch to catted headers for the test and then switch back afterwards? The Kooks headers I was looking at have a connection pipe that (I believe) would mate to the NPP exhaust. Why not just purchase this catted connection pipe and swap it on before the test, and then swap back to the offroad connection pipes afterwards? It seems a lot easier than replacing the stock headers.

Has anyone tried this? If you get a tune to resolve a CEL for the Kooks Headers with Offroad Pipes, and then you replace the offroad pipes with catted pipes, would the CEL return? Would you have to jump between tunes depending on the connection pipe used?

[pyroguy]

First of, welcome to the forums!

To answer your questions, if you have emissions testing, you will need cats otherwise you will not pass even with a tune. The noticeable difference you are describing between catted vs catless is probably rasp in the exhaust. Yes catted headers are less raspy which can be thought of as “less mean” sounding to some. Personally I liked having less rasp and more of an exhaust note.

If you switch between catless and catted pipes you will need a different tune otherwise you may experience a CEL or your emissions may end up off and you could fail the test.

Good luck in your choice. If you’re concerned about having the meanest sounding car out here, you may consider some no weeds diverters to add a little extra punch to the car.

[who-dat]

I work with vehicle emissions systems, but in another state. Depending on how NC handles their testing besides a visual check, you can get around it depending on your tuning software. PM me if you want to discuss

[christianchevell]

The rasp is usually less with high flow cats and that's about it along with the GAS smell being a lot less but that's dreaming....as with headers you will need a tune as the places the o2 sensors are at change and you get delayed response codes from the change and have to disable the rears which both work against keeping the exhaust clean along with the car performing better tuned with a adjusted AFR. For you I would just recommend a dual mode with the fuse pulled...you have to be able to smog it and then if you find its OK...( its legal here to swap out for headers in Oregon from stock OEM as many exhaust manifolds break over time being cast iron), You will need cats and a perfect not too rich tune to be able to clear smog ..... And might be better served by using some cut outs for added noise if that's what you want. I do love the sound of my cammed car and it has excellent exhaust burble downshifting or coming off the gas sometimes/engine breaking but its due to the tune and the dual mode and is helped most likely from the heat of the hot high flow cats helping ignite that left over gas from the fuel cut off in my tune. But stock my 13 with dual mode always had some burble.....decel pop.

[Vanthios]

Originally Posted by pyroguy

First of, welcome to the forums!

<3

Originally Posted by pyroguy

If you switch between catless and catted pipes you will need a different tune otherwise you may experience a CEL or your emissions may end up off and you could fail the test.

Let's say that I had a tune for both catted headers and non-catted headers. I'm not really that familiar with implementing a tune on a car, but wouldn't it just be uploading a file to the vehicle's onboard computer? If I had the file for both setups (catted headers and non-catted headers), couldn't I just swap the programming when I swap out the connection pipes? Could the slight difference in installation when swapping between connection pipes result in issues with the tune? That is, if I had a tune for the original installation of headers with cat-less connection pipes, switched to catted connection pipes for an inspection, then switched back to cat-less connection pipes following the inspection, is there a possibility that minor differences with the cat-less connection pipe installation could result in CELs even with the cat-less header tune? Sorry if this is at all confusing; I'm just trying to iron out the practicality of spending all this money to get the sound I want and be in the clear for inspections.

Originally Posted by pyroguy

If you’re concerned about having the meanest sounding car out here, you may consider some no weeds diverters to add a little extra punch to the car.

Would a NOWEEDS diverter have any issues in an emissions test? I mean anybody who looks at it would immediately know its purpose and that, when open, it's bypassing the cats. It's pretty neat how you can switch it on and off, though. I can see how you could argue in an inspection that all the required hardware is still present.

Originally Posted by who-dat

PM me if you want to discuss

Will do! Thanks!

Originally Posted by christianchevell

you have to be able to smog it and then if you find its OK

This is equivalent to breaking the exhaust in, correct? I'm buying used (55K miles) so I have a good feeling that's already taken care of
I have the fuse pulled on my RS and it's fantastic. From what I've heard I really , really like the sound of the SS with LT headers and the NPP exhaust; I'm just trying to find a good intermediate between what I want and what's legal.

[pyroguy]

Originally Posted by Vanthios

Let's say that I had a tune for both catted headers and non-catted headers. I'm not really that familiar with implementing a tune on a car, but wouldn't it just be uploading a file to the vehicle's onboard computer? If I had the file for both setups (catted headers and non-catted headers), couldn't I just swap the programming when I swap out the connection pipes? Could the slight difference in installation when swapping between connection pipes result in issues with the tune? That is, if I had a tune for the original installation of headers with cat-less connection pipes, switched to catted connection pipes for an inspection, then switched back to cat-less connection pipes following the inspection, is there a possibility that minor differences with the cat-less connection pipe installation could result in CELs even with the cat-less header tune? Sorry if this is at all confusing; I'm just trying to iron out the practicality of spending all this money to get the sound I want and be in the clear for inspections.

Would a NOWEEDS diverter have any issues in an emissions test? I mean anybody who looks at it would immediately know its purpose and that, when open, it's bypassing the cats. It's pretty neat how you can switch it on and off, though. I can see how you could argue in an inspection that all the required hardware is still present.

If you had a tuner and two tunes you could probably get away with it. However, when installing a tune many inspection stations can see the last time you flashed your computer and depending on how strict they are may require you to drive 500 miles before they will pass your car. For me the hassle wasn't worth it.

As for the Noweeds, they go immediately behind your cats or mid-pipes. Even with a straight piped car these add volume because you don't have to travel through a bunch of piping. When open they're wicked loud. Sound greasy, but loud.

[Vanthios]

Originally Posted by pyroguy

If you had a tuner and two tunes you could probably get away with it. However, when installing a tune many inspection stations can see the last time you flashed your computer and depending on how strict they are may require you to drive 500 miles before they will pass your car. For me the hassle wasn't worth it.

Alright; let me throw another idea at you. What if you had two of the computer chips. One with the cat-less headers tune and one with the catted headers tune, and then just switch them out when the connection pipes are switched out. I suppose this only adds to the labor associated with every emissions test.

[pyroguy]

Originally Posted by Vanthios

Alright; let me throw another idea at you. What if you had two of the computer chips. One with the cat-less headers tune and one with the catted headers tune, and then just switch them out when the connection pipes are switched out. I suppose this only adds to the labor associated with every emissions test.

MOPAR cars it's easy and almost recommended to have a second ECU instead of reprogramming. I'm not sure about GM vehicles. Anything is possible and doable with enough time, money, and effort. For me it was just easier to run cats and not worry about the hassle. I'm sure you can find a shade tree mechanic that would clear you for a case of beer or an extra $20 and skip the extra steps.

[Synner]

No emissions center knows what a stock tune or tune counter looks like. It's a question of how butt puckered are they on visual cat vs stock cat visual and does your tune have the correct zero emissions awaiting checksum issue resolved within the tune. I don't know any in VA or NC that suck tailpipe emissions so no need for 2 tune anything unless that has changed.