Headers Catless vs Catted, sound difference? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

BlackMaro14 · 02-03-2017, 02:36 AM

Hello Gentlemen,

This is my first post ever, i looked everywhere throughout the forums but couldn't find what i was looking for, so i would humbly as for your greater knowledge and expertise on this field. So I bought a Kooks Headers 1 7/8 x 3 inch with the Off-road connection pipes (catless) and planning on installing them on my stock L99 exhaust on my camaro because i want it to be as quiet as possible at idle (if possible i want to even sound stock at idle), and only be loud at WOT.

So my question's are:

1. With this setup in mind (kooks, off road pipe, stock catback) would it be louder at idle then lets say the High Flow catted connection? and if so by how much? is it noticeable? and either way ... are they both gonna be noticeably louder at idle than stock manifolds even though im running stock catback?

2. the kooks headers and connection pipes are 3 inches correct? but the stock cat back is 2.5 inches ... would their be any fitment issues? any cutting or wielding needed in this case? or will they bolt on perfectly even though its 2.5 vs 3.0?

PS: i know the difference in terms of smell, hp etc. so please i just need to know strictly about the questions i have asked, and if its possible and someone has a video of the setups i have mentioned, it would be great if you could share it with us all

Thank you for your time, and i hope i would get some informative responses on your behalf.

Thanks again, good Sir's

BlackMaro14 · 02-03-2017, 04:55 AM

com'on guys ... over dozens of views but not a single help from anyone?? ... please i need this, i need your help guys.

mma · 02-03-2017, 05:22 AM

i -think- keeping your stock mufflers will keep the sound quieter at low RPMs and will scream at WOT, at least that is how it is in my car with 1 7/8 catless headers w/ NPP. catless will definitely be louder than having a cat. don't think you can achieve the quietness of stock after going with LTH

i dont know much about kooks, but you should have the 3 to 2.5 catless/cat connection pipe

you'll find plenty of videos around, just gotta search

MR.Sarge · 02-03-2017, 07:51 AM

No such thing as quiet with headers lmao. You will fall to lead foot syndrome after 5 mins with it on.

I have Kooks LT headers on my car with NPP exhaust and have both offroad and cats to swap out for emissions testing, I know **** me right? stupid Canada.

At Idle you wont notice much of a sound difference loudness wise IMO between the two catless is slightly raspier if I had to give an explanation? But it will definitely be louder on startup and slightly more on idle

Biggest difference is smell .. BIG time, but you get use to it. HP between both, thats negligible, MAYBE if you're lucky 1-3HP it makes no noticeable difference.

MrChrisLS3 · 02-03-2017, 08:00 AM

It's pretty amazing how much sound the stock cats absorb, so yeah, headers and high flows are going to increase the sound, there's really no way around that. However, I think, with the factory cat back, it's going to be only slightly louder than stock, with a little more "bark" perhaps.

Fitment, I believe the Kooks set up is designed to match up for a direct fit.

JLGO · 02-03-2017, 08:48 AM

Quote:

Originally Posted by BlackMaro14

com'on guys ... over dozens of views but not a single help from anyone?? ... please i need this, i need your help guys.

I have in my l99 vert bbk lt ceramic coated headers, custom catback exhaust and legato mufflers. The only thing that was left stock was 12 inches of the stock exhaust that has the exhaust flaps.These exhaust flaps come only on convertibles it opens when the gas pedal is applied. It is kind of loud when it starts from cold and at full throttle. Is quite when is warm and at idle speed. Hope this helps.

JLGO · 02-03-2017, 08:58 AM

I forgot to mentioned those exhaust flaps only comes in verts stock exhaust system. Maybe you can get those on ebay. I wanted quite at idle and at cruise, I was advice by the muffler guy to keep them and he was right. The car is only loud on cold starts and half to full throttle.

DRKS1D3 · 02-03-2017, 09:51 AM

Mods are in my sig. If you want your car to sound stock at idle, leave it stock. The cats are most restrictive portion of the exhaust. When the stock cats are removed or replaced with high-flows, the sound comes alive.

My car:

Gunmetal Speedster · 02-03-2017, 08:28 PM

Quote:

Originally Posted by BlackMaro14

So my question's are:

1. With this setup in mind (kooks, off road pipe, stock catback) would it be louder at idle then lets say the High Flow catted connection? and if so by how much? is it noticeable? and either way ... are they both gonna be noticeably louder at idle than stock manifolds even though im running stock catback?

2. the kooks headers and connection pipes are 3 inches correct? but the stock cat back is 2.5 inches ... would their be any fitment issues? any cutting or wielding needed in this case? or will they bolt on perfectly even though its 2.5 vs 3.0?

1. Off road pipes will be slightly louder than hi flows. Not so much that you would be able to notice a huge difference. The sound will however be a little bit more raspy, but if you have NPP you will love it. At idle (other than start up) you wont have an issue with it. It wont be a game changer, so you should be set there.

2. You shouldn't have any issues with connecting the two!

Good luck!

christianchevell · 02-03-2017, 08:40 PM

With a l99 you will want to ditch the stock trashcans; (mufflers), and the stock suitcase resonator and then the sound will really come alive, but for sake of the ticket possibility I always advise to use HFC otherwise your illegal as the vehicle came equipped with HFC. I am in a state that allows for the stock exhaust to be changed to headers even; for purposes of exhaust replacement when needed so that is lucky yet there is PDX where they have smog testing and even HFCs can not clean it up enough when cammed for smog.. And by the way HFCs are not restrictive at all so the noise difference is little yet they do help make a great deceleration popping with a manual and the dual mode open. And raspier is usually the thought of no cats. Me I need to install a better tunnel brace which helps exhaust vibrations....

InFiD3ViL · 02-03-2017, 10:05 PM

You are going to need to ditch the catless off-road pipes and get some high flow cats if you want it to be that quiet.

Keep in mind, you are losing 4 cats by going with longtubes and off-road pipes. That is a lot of noise reduction you are losing.

In regards to question #2, I have TSP headers. Their off road pipes neck down to 2.5 inches to meet the stock system. I would assume the Kooks have a similar setup, but I have been known to be wrong.

Gunmetal Speedster · 02-04-2017, 03:11 AM

Quote:

Originally Posted by InFiD3ViL

You are going to need to ditch the catless off-road pipes and get some high flow cats if you want it to be that quiet.

Keep in mind, you are losing 4 cats by going with longtubes and off-road pipes. That is a lot of noise reduction you are losing.

In regards to question #2, I have TSP headers. Their off road pipes neck down to 2.5 inches to meet the stock system. I would assume the Kooks have a similar setup, but I have been known to be wrong.

Same with Speed Engineering

BlackMaro14 · 02-04-2017, 09:14 AM

Quote:

Originally Posted by christianchevell

With a l99 you will want to ditch the stock trashcans; (mufflers), and the stock suitcase resonator and then the sound will really come alive, but for sake of the ticket possibility I always advise to use HFC otherwise your illegal as the vehicle came equipped with HFC. I am in a state that allows for the stock exhaust to be changed to headers even; for purposes of exhaust replacement when needed so that is lucky yet there is PDX where they have smog testing and even HFCs can not clean it up enough when cammed for smog.. And by the way HFCs are not restrictive at all so the noise difference is little yet they do help make a great deceleration popping with a manual and the dual mode open. And raspier is usually the thought of no cats. Me I need to install a better tunnel brace which helps exhaust vibrations....

Bro ... with all due respect, did you even read my post ?

BlackMaro14 · 02-04-2017, 09:15 AM

Quote:

Originally Posted by InFiD3ViL

You are going to need to ditch the catless off-road pipes and get some high flow cats if you want it to be that quiet.

Keep in mind, you are losing 4 cats by going with longtubes and off-road pipes. That is a lot of noise reduction you are losing.

In regards to question #2, I have TSP headers. Their off road pipes neck down to 2.5 inches to meet the stock system. I would assume the Kooks have a similar setup, but I have been known to be wrong.

Is the difference that noticeable between the two?

02-03-2017, 02:36 AM	#1
BlackMaro14 Drives: '14 Camaro SS L99 Join Date: Feb 2017 Location: KW Posts: 14	Headers Catless vs Catted, sound difference? Hello Gentlemen, This is my first post ever, i looked everywhere throughout the forums but couldn't find what i was looking for, so i would humbly as for your greater knowledge and expertise on this field. So I bought a Kooks Headers 1 7/8 x 3 inch with the Off-road connection pipes (catless) and planning on installing them on my stock L99 exhaust on my camaro because i want it to be as quiet as possible at idle (if possible i want to even sound stock at idle), and only be loud at WOT. So my question's are: 1. With this setup in mind (kooks, off road pipe, stock catback) would it be louder at idle then lets say the High Flow catted connection? and if so by how much? is it noticeable? and either way ... are they both gonna be noticeably louder at idle than stock manifolds even though im running stock catback? 2. the kooks headers and connection pipes are 3 inches correct? but the stock cat back is 2.5 inches ... would their be any fitment issues? any cutting or wielding needed in this case? or will they bolt on perfectly even though its 2.5 vs 3.0? PS: i know the difference in terms of smell, hp etc. so please i just need to know strictly about the questions i have asked, and if its possible and someone has a video of the setups i have mentioned, it would be great if you could share it with us all Thank you for your time, and i hope i would get some informative responses on your behalf. Thanks again, good Sir's

02-03-2017, 07:51 AM	#4
MR.Sarge Drives: 2015 2SS/RS 1LE Join Date: Nov 2011 Location: Windsor, ON Posts: 511 View My Garage	No such thing as quiet with headers lmao. You will fall to lead foot syndrome after 5 mins with it on. I have Kooks LT headers on my car with NPP exhaust and have both offroad and cats to swap out for emissions testing, I know **** me right? stupid Canada. At Idle you wont notice much of a sound difference loudness wise IMO between the two catless is slightly raspier if I had to give an explanation? But it will definitely be louder on startup and slightly more on idle Biggest difference is smell .. BIG time, but you get use to it. HP between both, thats negligible, MAYBE if you're lucky 1-3HP it makes no noticeable difference. __________________

02-03-2017, 08:40 PM	#10
christianchevell old school chevy rodder Drives: 2013 2SS/RS Manual,DM exhaust,CRT Join Date: Jul 2012 Location: Oregon Posts: 5,588 View My Garage	With a l99 you will want to ditch the stock trashcans; (mufflers), and the stock suitcase resonator and then the sound will really come alive, but for sake of the ticket possibility I always advise to use HFC otherwise your illegal as the vehicle came equipped with HFC. I am in a state that allows for the stock exhaust to be changed to headers even; for purposes of exhaust replacement when needed so that is lucky yet there is PDX where they have smog testing and even HFCs can not clean it up enough when cammed for smog.. And by the way HFCs are not restrictive at all so the noise difference is little yet they do help make a great deceleration popping with a manual and the dual mode open. And raspier is usually the thought of no cats. Me I need to install a better tunnel brace which helps exhaust vibrations.... __________________ 2021 Wild Cherry ZL1 A10, Sunroof, Data, Carbon, Nav, RotoFab Dry CAI, Elite x2, Borla ATK, Driveshaft shop

02-03-2017, 10:05 PM	#11
InFiD3ViL Drives: 2010 CGM 2SS/RS LS3 Swapped A6 Join Date: Sep 2016 Location: Spring Hill, FL Posts: 4,570	You are going to need to ditch the catless off-road pipes and get some high flow cats if you want it to be that quiet. Keep in mind, you are losing 4 cats by going with longtubes and off-road pipes. That is a lot of noise reduction you are losing. In regards to question #2, I have TSP headers. Their off road pipes neck down to 2.5 inches to meet the stock system. I would assume the Kooks have a similar setup, but I have been known to be wrong. __________________ 2010 CGM Camaro 2SS LS3 Swapped A6 - GPI LS3 SS1 .647/.638, (224/237, 112 +4, 7º overlap) on CamMotion 8620 core, BTR Platinum .660" Dual Spring kit w/titanium retainers, CHE bronze trunnion upgrade, stock heads milled @ .015, Melling HV 10296 oil pump, TSP 1-7/8" long tube headers (W/Catless Off-road Pipes), Corsa Xtreme 3" Catback, GPI Ported/Rod Mod Intake, Stage 2 Ported Throttle Body, Vararam OTR CAI, Mike Norris Gen 2 catch can + GM 1LE clean side separator, 160º thermostat - Megan Racing adjustable coilovers (lowered 1.75"), MRR M017 10/11" wheels-Tuned by Ryan @ GPI

02-03-2017, 04:55 AM	#2
BlackMaro14 Drives: '14 Camaro SS L99 Join Date: Feb 2017 Location: KW Posts: 14	com'on guys ... over dozens of views but not a single help from anyone?? ... please i need this, i need your help guys.

02-03-2017, 05:22 AM	#3
mma Drives: 1LE Join Date: May 2015 Location: California Posts: 267	i -think- keeping your stock mufflers will keep the sound quieter at low RPMs and will scream at WOT, at least that is how it is in my car with 1 7/8 catless headers w/ NPP. catless will definitely be louder than having a cat. don't think you can achieve the quietness of stock after going with LTH i dont know much about kooks, but you should have the 3 to 2.5 catless/cat connection pipe you'll find plenty of videos around, just gotta search

02-03-2017, 08:00 AM	#5
MrChrisLS3 Drives: 2018 1SS M6 Join Date: Nov 2014 Location: Houston Posts: 2,617	It's pretty amazing how much sound the stock cats absorb, so yeah, headers and high flows are going to increase the sound, there's really no way around that. However, I think, with the factory cat back, it's going to be only slightly louder than stock, with a little more "bark" perhaps. Fitment, I believe the Kooks set up is designed to match up for a direct fit.

02-03-2017, 08:58 AM	#7
JLGO Drives: 2015 Camaro SS convertible L99 Join Date: Nov 2016 Location: Orlando, FL Posts: 245	I forgot to mentioned those exhaust flaps only comes in verts stock exhaust system. Maybe you can get those on ebay. I wanted quite at idle and at cruise, I was advice by the muffler guy to keep them and he was right. The car is only loud on cold starts and half to full throttle.