whenever i rev my car up and then the RPMs are comming back down.....right before it gets to idle lets say 1500-1000, the exhaust makes a weird hissing noise. i'm running !muffler with aftermarket tailpipes and stock manis/ cats/ ypipe. anyone have suggestions on what this could be? my dad nd i are gonna get it on a lift today to check it out, just wanna se if anyone has suggestions. mods are in sig if that helps any.

 

anyone know? we just had it up on the lift and everything looked fine. everything sounds fine when it revs it, only when its comming back down to idle, right before it gets to idle it makes a weird sound like somethings loose inside the exhaust, just a weird noise thats hard to explain.

 

don't have a clue......i do think you are building some serious turbulence in your exhaust flow in that area just after the axle......is that a dual exhaust tip welded in there?? i might be wrong but i would think about re-evaluating the exhaust setup after axle......maybe just maybe that turbulence is creating the hissing sound.

 

nah its just a lil ypipe we had laying around the shop. my dad does exhaust work for a living so we just rigged it up on our own. how would we be able to re do this, maybe like the after axle of a loud mouth is done? it has the y shape comming straight done from the axle. i guess ill start a new thread and see other's !muffler setups.

 

yeah mine y's off right over the axle.....i would do something like that if i were you and see if the noise goes away.....that may very well be your problem.....but have you checked all your joints, clamps, etc. for leaks.....maybe a stupid question but you never know......by the way is that 2.5" pipe....cuz if so you could probably put that y you already have in there before the axle and then run the two pipes over the axle, i've seen several people with TD setups done in a similar way at least that way it would save you a little cash cuz you could use parts that you already have.

 

<edit> dude.....no bullshit, i would just get rid of that entire setup and get a new catback, unless you're like me and money is a serious issue......cuz that does look like one 2.5" pipe over the axle and that has to be choking the **** out of your motor and combined with that turbulent area after the axle.....can't be making for an efficient exhaust.

 

moneys a serious issue for me too.....but we've got plenty of 3 inch and 2.5 piping to do whatever we need to do. i might just put the Y right before the axle and run 2.5 dual over the axle or just put the y comming down from the axle.

 

you need at least 3" pipe on these cars for an intermediate pipe up to the axle....then i would run 2.75" pipe out each side.

 

well the extreme pipe bend isn't the problem making the noise. i cut the pipe right after the axle and cranked her up bfore i went any further and it stil made the noise so idk what it could be, its nothin after the axle i do know that.

 

**** man!!!!! ya got me.....i wish i could be more of a help, i would have the the turbulent air swirling around in there might have been capable of making that noise, but if it's doing it right off the y-pipe.......i'm at a loss, u haven't done a LT install so i know it can't be a loose header bolt leaking.......again have you checked all the joints on your exhaust? That is the only other explaination i could possibly think of, but if it's hissing and not ticking, that would have to be one HELLUVA exhaust leak. Sorry man don't know what else to tell you....maybe if someone else chimed in you might get some real help......

 

yea it wasnt a big deal to put it in the air and cut it, my dad owns a shop so i did it on my own and did hafta pay. it's got me stumped too. my dad checked underneath and said the cats are good, and checked for leaks with the little earpieces you put it kinda like a stethescope. so....no leaks, cats are good, and exhaust after the axle is fine. there can't be anything wrong in the I-pipe section, so it must be something with the manifolds, it has to be! i may let one of his buddies take a look at it this week and see if they can figure it out, cause its buggin the hell outta me! with everything i've said, i dont think puttin a new muffler on it will silver any problems at all, it might just tone it down a little.....anyone else have ANY ideas? i'm open to trying anything.

 

i finally found clips of other cars that make the same noise...notice on the revs....right as it comming down to idle it makes the noise..anyone know wahts causeing this?
http://www.ls1sounds.com/headers_cut...tock_98Z28.MPG
http://www.ls1sounds.com/my_car/cuto...k_chad_rev.wmv

note....thi is the same exhaust i have on both cars; stock manis, cats, ypipe, no muffler (cutout)

 

I would just have to say that you have great scavenging.

 

and how's this done away with?

 

that is a good thing that you dont want to get rid of.

 

a good thing that makes a god awful noise thats embarassin? id rather just have it gone lol.

 

could be loose honeycomb in the cats....
i have that...the **** like flakes off inside...then it rattles around and thats what you hear....at least thats what it is on my SS...

check into that!
Erik

 

could be loose honeycomb in the cats....
i have that...the **** like flakes off inside...then it rattles around and thats what you hear....at least thats what it is on my SS...

check into that!
Erik

 

yeah i listened to the vids....id say its loose particles of honeycomb vibrating in your cats....notice all of those cars have cats....check out a cr with !cats and it diesnt make that noise....
im get rid of my cats eventually but ive got that too...let us know
erik

 

how much different would mine sound high flo cats? i figured id need to replaec them anyway sinc they're bad.