rsodeputy61

I know, I know, this question gets really old..........but, I'm getting the common "jackhammer" rasp in the low 2k rpm range. I put a 4" magnaflow bullet in the I pipe and it did help some, but not enough. Was wondering if anybody knows how it would sound and help the rasp if I put a flowmaster single chamber in the I pipe instead of the bullet and then still let it exit through the gmmg??? I am determined to not run cats and love the gmmg except in this rpm range. I just wonder if the single chamber flowmaster would equalize the pressure out enough to kill that freakin machine gun....and possibly even deepen it some more..

gtabandit2

rso have you tried doing a search? You may want to try a third chambered muffler such as the stainless works to match the gmmg always rememeber the longer the tube the less db and more sound "tuning". If not you may want to try classic chambered exhaust "powersticks" for a less xpensive route I have them and they sound great!!

rsodeputy61

aaaahahahahaha....i guess u have one for sale, huh? tick, tick, tick....inside joke.

ChocoTaco369

Just put cats in the setup.

There is no argument to not get cats over a Flowmaster single chamber.

2 cats will outflow a single chamber in the I-pipe, so the horsepower argument doesn't work.

A single chamber is ~$80 shipped, and you can get two aftermarket cats for roughly the same price, so the cost argument doesn't work. Hell, you can get ebay bullet cats for less than the price of a single chamber.

Cats will do more to get rid of rasp than any pseudo-muffler in the I-pipe ever will.

rsodeputy61

it's not about horsepower. i understand that cats only drop it a few h.p......it's about the sound. i heard one the other day and the cats tone it down a good bit. other than that small rpm range, the gmmg w/out cats sounds freakin awesome. i want to keep it loud as it is now, just want to find a way to kill the "machine gun" effect. i could probably do it with a muffler with packing in the I pipe, but again that's gonna quieten it down a good bit.

ChocoTaco369

Get a set of Magnaflow 59959 cats. That's what I have. It doesn't "tone it down" very much...or maybe none at all. They're so incredibly high flowing, it's like they're not even there. My setup almost smells catless. My exhaust has a very rich smell to it, but it's just missing the "gasoline smell" and noxious odors. The cats will still tone down the rasp, though.

RevGTO

iTrader: (12)

I used a classic chamber medium powerpack in my I-pipe. It took that AND cats to conquer rasp.

rsodeputy61

how does it sound? did it tone it down much?? i would just rather avoid installing cats. if i've read the past posts correctly, the rasp is caused by the firing order of the ls1. i just thought maybe a flowmaster single chamber would be enough to help equalize the exhaust pressures out and take care of it. i don't see how cats would outflow a single chamber....guess no one knows for sure.

RevGTO

iTrader: (12)

It sounds good - it softened the sound and diminished the pulsations that cause the rasp effect. But I added it AFTER I put on the cats. I am hyper-sensitive to rasp and I had some even after cats. The Powerpack cut more of it out. Adding Hooker resonator tips finally zeroed it out.

JScamaro

iTrader: (6)

My gmmg has rasp around that same rpm range even with cats.

2_wacko

iTrader: (2)

Cats is the way to go with GMMG.

ChocoTaco369

Rasp is caused by the y-pipe setups of the LS1 f-body. Y-pipes, simply put, cause rasp. It takes exhaust from 2 sides of the engine and clashes them together into a single stream. It would take the perfect y-merge to completely erase rasp, but there's no such thing. You can do things like get a Flowmaster y-merge as that will get you as close as possible to getting rid of rasp, but nothing's 100% perfect.

Blaming the firing order of the LS1 for rasp is BS. The LS1 has the same firing order as Mustangs and they don't rasp much at all. Why? Because Mustangs have H-pipes and true duals from the factory and the piping on Mustangs are about perfectly equal. That's why Mustangs don't rasp. A custom H-pipe TD setup will get you as close as possible to getting rid or rasp, but it's not 100% on the LS1 f-body because our cars weren't designed for true duals and you have to make funny bends in the pipes to get them to fit so the lengths aren't equal.

Funny thing is, if you put TD's with an H-pipe and Flowmasters on your car, it sounds just like a Mustang, just a little higher pitched because of the aluminum block. That's because the firing orders are the same

If you've seen the inside of a single chamber, you'd see they're not straight through. They have to go around a triangular shaped bend. It slows things down a bit, and you're limiting yourself to squeezing all your exhaust through one 3" opening. The inside of a set of Magnaflow 59959's are so porous you can see through them, and you're only sticking 4 cylinders of the engine through one instead of forcing all 8 around a triangular bend like on a single chamber.




There's nothing to these cats, really. They're a work of art.

SweeTbone

iTrader: (8)

+3 My **** is still loud with cats and virtually rasp free. Even before the Heads/Cam.

nytmare1

iTrader: (7)

When I first had my longtubes installed, I used an ORY. I also had a Stainless Works chambered exhaust system. It's similar to a GMMG except it has a chambered pipe in the "I". It was very LOUD and raspy! I had to granny it around town for fear of cops pulling me over.

I ended up having some stainless steel Thunderbolt cats welded in which quieted it down a bit more than I wanted, but the rasp was completely gone. So... to brighten it up a little bit, I had the chambered "I" pipe replaced with a 3" straight pipe. The car now has the sound I was looking for. It's relatively quiet when I want it to be, but she screams and growls when I get on the gas. I'm very happy with the sound now!

Marc

rsodeputy61

Well, from what i've read and from other's testimonials on here, the flowmaster single chamber flows really well. In addition, i understand it's not straight through, which is my whole point for wanting to try it. I have a straight through magnaflow bullet now and it didn't change it very much. I think the single chamber may be just enough to adjust the flow to change the sound coming out of the y merge. Also, it's already being squeezed through one 3" opening in the I pipe so I don't see it limiting anything.

sixvi6-camaro

iTrader: (9)

flowmaster 1 chamber might as well be straight through though. its a hollow case with 3 V shaped baffles in the middle. you can shine a light into the inlet and see the light from the outlet. Heck I can reach my skinny hands into the inlet and outlet and touch my fingers together... lol!

rsodeputy61

You're Incorrect. My neighbor, gtabandit, has a 3rd gen with headers, ory and a catback with zero rasp. If it was simply from the merge on the y pipe, then cats wouldn't help either because it would have already passed them going into the merge.

I wonder what it would do if you came just before the merge on the y pipe and installed a crossover tube such as in the "h-pipe" to balance the pressures between the tubes before the merge. I am determined to try one/both of these ideas to possibly come up with a solution which may help others with the ORY setups who don't want to run cats and don't want to sacrifice ground clearance with true duals.

ChocoTaco369

People on here think the single chamber flows well because they look through it and assume so. Then, more people hear that info and spread it around. It's nothing more than a rumor. I've never seen it flowbench tested. There's no info about how much air a single chamber can flow. It's all BS. Does it flow well? Probably, but it's not going to outflow two high-flow cats.

ChocoTaco369

You're missing my point. There's no way it's 100% rasp free. You just may not be able to hear it. Is he running a muffler, too? A muffler will help quiet the rasp to the point where you won't be able to hear it. Just because you can't hear it doesn't mean it's not there, though. Tell him to remove his muffler, then see if there's rasp.

You can try that...but I don't see it doing much...who knows...

sixvi6-camaro

iTrader: (9)

.. on the flipside where is all the info on your High flow cats? How can you make the assumption that Hi Flow cats are soo much better without presenting data on those either?

lol.. yeah the Rasp still exists to all those people that live inside the I pipe of the car before the muffler.. Very Philosophical.. Man I wonder if Rasp still exists in my true dual exhaust now because at one time I ran an ORY that rasped.. or if my car was rasping away but nobody was around to hear it would the Rasp exist?