What causes this. Not the no cats, headers, exhaust answer. But what exactly causes this. Mustangs do not have it from what I can tell. For some reason I'm getting more rasp than I expect. I have true duals (cut-up tsp duals with sweet thunders 18") I'm just looking for a way to get it down. I don't want to put cats on and I want to make the same power. Ever since I put in the 4.10 gears the rasp seems more evident. It's pretty annoying and I though true duals didn't have it at all. If I knew how to make a clip I would, but I don't. It's only on part throttle driving. If you give half gas you don't hear it, even though it crosses the "rasp zone"

Here are some pics if it makes a difference as to how the pipes are layed out.

http://img.photobucket.com/albums/v4...eetthunder.jpg

This pic is with when I had cats on. Now there is just straight pipe there. The rasp increased slightly without the cats but not much at all.

http://img.photobucket.com/albums/v4...atsb4xpipe.jpg

 

In the past, I have heard rasp explained as the sound waves created when the exhaust pulses "collide" at the intersection point of the y-pipe...not sure if this correct, or even the type of answer you are looking for...anyway, seemingly y-pipe collectors that can smooth out the merging of the two pulses create less rasp...

 

I've heard that as well. That is why I'm confused as to why my car is rasping now. I have an x-pipe (tsp) and the duals are dumped. I thought that would get rid of the rasp.

 

I always thought rasp is from unequal length piping. For example macs are very raspy and have very unequal primary tubes. On the other hand SLP headers are much smoother and are supposedly an equal length header.

Supposedly, if a ypipe was equal length it would sound and perform as well as an xpipe. I think not all xpipes are the same. If the tubing is before the xpipe is unequal in length, the exhaust tone will be not as smooth.

Thats my .02$

 

I also hear this "rasp" noise and have been through many different exhaust setups. I have the same set up as you 777, do you notice its really audible when your next to something? For instance maybe crusing part throttle next to an embankment? I have just learned to live with it, I have tried just about everything. I have a stock cam to, so I think that makes it more audible because the exhaust dosen't get real choppy. I have learned thats just how these cars sound when you slap headers on them, let someone else drive your car (if you can bear it) I cant make out the same noise outside the car. It must be a reasonant sound only the passengers can hear.

 

hmm..well if that's the case. I *might* end up cutting the mufflers off and having someone fab me up a nice TD system using the TSP X. That way it won't cost me so much.

 

I can somewhat hear it when my dad is driving the car and I'm outside. It's not the same. It's not near as bad as inside the car. Worst rasp for me is in 5th gear right around 40mph. Note that I have 4.10 gears though. So it'd proly be around 45 in a stock 3:42 car. I just know that the mustangs don't have this rasp. Everyday this mustand (loud, so has to have headers/no cats/exhaust) and it sounds as crisp as gmmg on a stock ls1. Only thing is it's twice as loud. I guess I'll just have to live with it. I want to get a good idea of how it sounds at the most distinct rasp zone, outside of the car. It'd be ok if it is just me hearing it, but if it sounds bad to everyone else then that's when things need to be changed.

I love the tone of the sweet thunders so I don't want to change and I don't want to change the tone by adding bullets somewhere.

 

Yea I get the rasp too, but I take solice in knowing that 99% the Stangs I run across don't stand a chance. I have heard alot of LS1's and any time they have LT's with no cats they seem to sound a bit raspy, funny though most of the TD ones I have heard are not that bad.

 

It's not NEAR as bad as my buddy's old LT1 with headers, ORY, and a Flowmaster cat-back. It didn't even sound good because the rasp was so bad. LT1's usually have less than an ls1 so I consider myself lucky I suppose.

 

I hear people talk all the time about rasp. I know its a undesirable exhaust sound but exactly what is it? Can anyone define it? The dictionary says "to grate upon; to irritate." Don't refer to sound clips, they don't convey the true sound of actually being in the drivers seat.

So what is rasp?

 

It's hard to describe but it is kind of a blatty sound. You will know it when you hear it.

 

Its a harsh tone that doesnt sound good.

 

I think rasp sounds like firecrackers popping in a coffee can.....sucks very much bad 'cause I have rediculous rasp on my car.

 

my old lt1 with headers ory and flowmaster, sounded good as hell, there was absolutely no rasp whatsoever. it sounded like a mustang. rasp is a wierd thing cause i know someone with your setup on his car and it sounds great.

 

There are other factors that have a greater role in how a car sounds that just the exhaust set-up. The LS1 is unique to the Mustangs and even the LT1 and older small blocks because of its unique aluminum block and head design. Without getting in to the nitty-gritty, the aluminum materials along with the design of the pistons, heads, cam profile, and other engine internals affect the sounds that are generated by the combustion process. The LS1 design just seems to be more of a rasp generator than other designs. There are ways to get rid of the rasp and change the sound with various exhaust combos, but the LS1 will still have some version of it’s unique sound regardless of the exhaust that you are running. It’s just the nature of the beast.

 

For starters, the louder and straighter the exhaust the more rasp you'll get. Stainless steel tubing also increases the rasp over mild steel. Undersized tubing will sometimes create rasp as well since backpressure is higher than a larger tube.

The more complicated causes are variable pressure changes within the exhaust. This is why so many fart cans on imports sound so raspy. 1-1/2" pipe into 4" mufflers...

 

Now I understand - thats a good description of rasp.

Over the years I've driven lots of standing start and circle track cars all with open headers. Never heard any rasp, just loud as race cars are.

Glad I'am running GMMG chambered on my LS1 cars. Never heard any rasp from them.

 

Dam I can how that exhaust would have rasp. Put some straight through mufflers on there or just deal with it. I would give up 10 hp to not have rasp myself.
Eric

 

I welded in a 15" Borla XR-1 and it resolved 90% of my drone and rasp issues. I was pleasantly suprised...

 

I don't know, today wasn't that bad. It's just like when the exhaust tone changes. So it may not be as bad as I'm thinking. I just know my neighbors Trans Am is decently loud (3/4's of mine) and it sounds great, he has true duals with stock headers, no cats. The cam might have something to do with it as well. It's like the changing point between the low rumble and the deep screaming tone of the exhaust.