[Eric10905]

Anyone have experience with a header and exhaust system that did not get appreciably louder than the stock NPP? And still have valves/modes? Don't care if it's deeper, just not a lot louder.

Next I'll say, OK, I know many want louder exhaust. I say, Hey, to each their own, if that's what you like or want, you should! It's suppose to make you happy, not others.

I'm not a young man anymore, and in my youth with a '70 SS my experience was that the loud exhaust attracted, also, the wrong (read Mr Lawman) attention when I was standing on it. I don't expect that has changed. ;-)

I'm ready to make the header and/or exhaust mods as part of the bolt-on stage. And I am 'ok' with the loudness level of the current NPP system. I'd really love to not get any or much louder, but still capture as much of the HP gains as possible. Yeah, conflicting goals. Next I'll be searching for a clip of headers onto an existing NPP system, maybe with or without a secondary cat delete, whatever i can find.


thanks in advance and enjoy The Ride!

[JCunningham]

no aftermarket exhaust is going to be as quiet as the stock NPP. i have 1 7/8" headers with hi flow cats to flowmaster American thunder npp mufflers. it was slightly louder then i liked so i had some https://www.summitracing.com/parts/xfo-ct04-14s put on. i think that worked. I havent driven the car sense I had it done as it has rained every day i have had off in more than a month. videos dont do it justice. it quieted it down to were the voice commands could understand me

[cmeJATT]

I think the 2 exhaust that are mellow is

Stainless Works
Borla Type-S

Everything else will be crazy loud. Does anyone know of any other exhaust?

[enzia35]

Originally Posted by cmeJATT

I think the 2 exhaust that are mellow is

Stainless Works
Borla Type-S

Everything else will be crazy loud. Does anyone know of any other exhaust?

Yeah, the Borla Touring. Which is the S-Type axleback with the 60608 piece in the midpipe.

With headers, you're gonna be pretty gosh darn loud regardless.

[Driski]

I put Kooks 1-7/8 with green cats on and a tune. After that everything is stock (Stock NPP). Got a nice HP gain, a little deeper sound, and a bit louder at start up. Not excessively louder and no drone. I can still curse nice and quite. I would recommend E85 conversion if you have it in your area. Nice HP gain for a bolt on. Good luck with your decision. Happy Motoring!

[geaux_tigerss]

I put 2" TSP headers no cats to my factory NPP catback. With the NPP valves closed it isn't much louder than stock. NPP valves open..... wake the dead.

Before I did headers I had pulled the fuse on my NPP. Occasionally I would wake the wife and kids in the morning when I left for work. After headers I put the fuse back in and have been starting it in stealth mode. I haven't woken anyone since then.

So I guess to summarize, headers with NPP valves closed is quieter than factory manifolds with NPP valves open.

[Eric10905]

Originally Posted by JCunningham

no aftermarket exhaust is going to be as quiet as the stock NPP. i have 1 7/8" headers with hi flow cats to flowmaster American thunder npp mufflers. it was slightly louder then i liked so i had some https://www.summitracing.com/parts/xfo-ct04-14s put on. i think that worked. I havent driven the car sense I had it done as it has rained every day i have had off in more than a month. videos dont do it justice. it quieted it down to were the voice commands could understand me

Thanks for the reply, and esp the videos. I have a feeling i'm going to have to compromise here in wanting more HP and decibel level. You note a point i had not even considered - the in cabin voice commands. Mine is not a DD, but i really like, if possible, to keep some of the 'civil' aspects of this beast. ;-)
Thanks again

[Eric10905]

Originally Posted by cmeJATT

I think the 2 exhaust that are mellow is

Stainless Works
Borla Type-S

Everything else will be crazy loud. Does anyone know of any other exhaust?

Thanks, and it probably shows i'm just getting started on thinking of the exhaust portion of mods. I was thinking 1-7/8" on the headers, and had not thought of the 2". Unless i went with SC, i figured i might not need them. but if it helps on sound level, worth considering.
Thanks!

[Eric10905]

Originally Posted by enzia35

Yeah, the Borla Touring. Which is the S-Type axleback with the 60608 piece in the midpipe.

With headers, you're gonna be pretty gosh darn loud regardless.

thanks, yep, i suspect compromise is in the future.
Gig' Em!

[kropscamaro16]

i have afe power headers and exhaust but for awhile i only had headers with npp exhaust


it was was louder than stock and actually sounded really good but after i added the axleback it was just louder but doesnt really add anymore power but damn it does sound good on the track


https://www.instagram.com/p/BxK_-M0HP4R/

[Eric10905]

Originally Posted by Driski

I put Kooks 1-7/8 with green cats on and a tune. After that everything is stock (Stock NPP). Got a nice HP gain, a little deeper sound, and a bit louder at start up. Not excessively louder and no drone. I can still curse nice and quite. I would recommend E85 conversion if you have it in your area. Nice HP gain for a bolt on. Good luck with your decision. Happy Motoring!

Thanks, in my early stages here your step up is what i am leaning towards. In part due to sound, but in part due to cost. The headers (kooks or otherwise it seems) are pretty expensive, given the anticipated gain. E85 is in my plans as well. the plan at this point is addressing the intake system up to heads (including head porting if i can talk myself out of the $$), exhaust system, and fuel type.

Curious, any idea what hp you picked up with the kooks and green cats? (or was it with the E85 at same time)

[Umbriel]

If you have the NPP and want to be quiet just keep it, it is pretty tame in stealth mode and still has the ability to go into touring to be slightly louder. You'd probably never use sport or track if you don't want it too loud.

[Eric10905]

Originally Posted by geaux_tigerss

I put 2" TSP headers no cats to my factory NPP catback. With the NPP valves closed it isn't much louder than stock. NPP valves open..... wake the dead.

Before I did headers I had pulled the fuse on my NPP. Occasionally I would wake the wife and kids in the morning when I left for work. After headers I put the fuse back in and have been starting it in stealth mode. I haven't woken anyone since then.

So I guess to summarize, headers with NPP valves closed is quieter than factory manifolds with NPP valves open.

LOL, waking up the house. well, not funny if you're the one woke up, or have to deal with them afterwards.
Thanks for the comparison.
I'm a college FB fan, and i'd be safe to guess you're a LSU Tiger and/or fan.... i know it's a 6Gen forum, but as an Aggie i expect a reply could include Tiger meat, lol

[Eric10905]

Originally Posted by Umbriel

If you have the NPP and want to be quiet just keep it, it is pretty tame in stealth mode and still has the ability to go into touring to be slightly louder. You'd probably never use sport or track if you don't want it too loud.

might be what i do.... during the day, i don't worry about it too much. well, except for when i try to shove my foot through the floor board... I'm having fun and know the costs of same, but would love to avoid a ticket resulting from the fact that they HEARD, before they saw me. And trying to be respectful to younger neighbors, and not wake up their kids early in morning or at night. Might seem silly to some, but will see if i can find that just right compromise.