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 :cool::)

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

Thanks again, good Sir's :thumbup:

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

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

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.

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.

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.

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.

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: https://www.youtube.com/watch?v=pycd5-ejMmI

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!

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....

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

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

Is the difference that noticeable between the two?