recently installed the comptech headers on the atlp cat back exhaust i have and i kept the catalytic converter stock..

and on a cold start or if i leave my car for off for a hour or so... i get a raspy noise when i rev and drive in the higher rpms. but it fades away after the car heats up

i dont know what it can be.. i only changed the headers gasket that connects to the engine when i got it installed.

should i have changed the other gaskets too?? do i got a ehaust leak?
i did a search and most threads i found were about stock exhaust and resonators.

 

is it the exhaust sound thats raspy or something rattling

 

its the exhaust

 

This Thread Worries Me as I plan to keep the stock cat on my car due to gay CALI emissions laws. Hope Theres a simple fix to this

 

not much you can do, especially since you said it already goes away once it warms up
but if you must, i say put an additional resonator in there somewhere

 

id go back and tighten everything up, sounds like it may be a small leak to me, which when heated up, goes away.

 

are you sure its not the exhaust itself? look from your back bumper and follow the exhaust to the front. i think it might be hitting against the heatshield

i also have ct headers, stock cat and atlp

 

I'm pretty sure it's not hitting anything
It sounds like it's coming from by the catalytic converter

 

doable check the rear gasket on the back of the converter, some reason that seems like a harder one to seal

 

make sure the cats heatshield is on tight, that started rattling on me too

 

any updates?

 

i ordered the catalytic converter gaskets im gonna try to put them on tommorow

 

have you ever dynoed ur car kdawg? I never noticed how many mods you have

 

i will soon after i get a test pipe or hfc

 

Wait for your car to warm up before getting on it. It takes 5 minutes to warm up so take it easy until the temp guage moves. Besides, it's not good to run your car hard outside of its optimal operating temperature. Also, adding a resonator will probably not get rid of the cold start raspiness as I had it with headers only on my CL. It seems to be the small price you pay for the huge performance gain. Also, if you're sensitive to sound, you may want to think twice about the test pipe/hfc as that makes the biggest difference in sound IMO (I.E. DRONE!).

 

It's weird it also happens if I leave the car off for about an hour and start it and I start driving I can hear the raspyness around 3500 rpm

 

cause the exhaust has basically completely cooled off already, not much metal there to stay warm, let alone SS


and then with the HFC or test pipe, as said it will exaggerate any noises your already have, cause the cat does act like a muffler in a way, and it will only open the exhaust up more

 

So u guys are saying this noise might be coming from the headers?

 

not totally ^, but did you just finger tight everything first, then go back through them to finally tighten them

btw did you use new manifold gaskets on those headers when you installed them???, then also are all the studs holding them on to the head still attached, aka no snapped ones???

and the post right above yours for the hfc or test pipe, is just saying that it will be noisier then now, and is not for every one (btw the cat is not a muffler, it only acts as one in a way, never it's intended purpose)

 

its not that i start car in the morning and just start revving it i hear it when im driving too close to around 3700rpm.. and i know the hfc gonna make it loud i had one on my older car lol. but yeah i already get soo much drone with the atlp exhaust already and after i put the headers on it just became crazy loud. ive gotten used to it now just my passengers dont like it

my mechanic put it on for me he used a impact wrench and we also changed the gaskets where the header meets the engine...
and about the studs he would have told me if something broke off
i didnt get the gasket that goes between the down pipe... looks like O-ring

 

you mean the o-ring between the header and the cat???, or the one's between the manifold's and the j-pipe???


by the way, are the headers new, if so it should have included the gaskets in there

 

i got them used but they were in really good condition. and im talking bout the gasket for the j-pipe there the circular one time use ring gaskets

 

so if you mean the ones from the j-pipe to the manifolds themselves, i have reused mine a couple of times already , but anyways, take it apart and get one of them out, and take it down to your local auto parts store (carquest would probably be your best bet, followed by napa), and they probably will have a replacement, cause i remember reading somewhere the o-ring to the cat itself, is just a standard 2.5 inch one, so it would not surprise me if those other ones where also just standard ones too just smaller in size (like a 2" or so)

 

Your pretty much gonna have the rasp on cold start ups... I have the headers and ATLP and high flow cat and rasp is alot more noticeable on cold startups and acceleration aroun the rpm range you already stated.... It's pretty much unavoidable when you increase header tube size and increase he exhaust pipe size and the exhaust has no resonators.. The hfc is just gonna make it louder as well... But you get used to it.. Jus crank the music up and enjoy!

 

Damn that's exactly what my mechanic said. Oh well I guess I can tune out the noise it just sucks when you try to show your buddies how the exhaust sounds and u hear that annoying rasp and there all WTF

 

So the high flow cat makes the noise worse?

 

some, also depends on how load the exhaust and such is already though, but yes it will make it worse to an extent

btw a test pipe is even worse then a high flow cat

 

Haha I got a test pipe on the way I'll see how that turns out.. If the exhaust becomes unbarable then I'll sell it and just get a highflow cat and cut into the atlp exhaust and add a resonator to it