How to kill the rasp without cats or duals!!!
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Joined: Aug 2007
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From: Mississippi
How to kill the rasp without cats or duals!!! Well, I've finally gotten my exhaust set up where I want it. Since the H/C/I, it had become unbearably loud and the "hammering" from 2000 rpm to 2700 rpm was embarrassing
. I was determined to correct the rasp without cats and I wanted to keep the GMMG because I love the tone/sound and the way it's set up with my Corsa clones. The final result is a very deep exhaust that's still very loud, especially at WOT, but refined without the rasp. I had two 3" Dynomax bullets installed in the front of the Y-pipe where cats normally go (where the rear O2's are). It really cleaned it up and there are no issues with clearance, etc. I already had a Magnaflow bullet in the I pipe and it had helped a little when I was a bolt on set up but not much. It really only deepened the note.
The only install issue was matching up the round bullet opening with the oval y-pipe on the driver's side. The header collector fit perfectly inside the bullet opening on one end and we made the bullet opening kinda oval and kinda rounded the y-pipe so it'd match on the other end.
So those of you with rasp may want to consider this instead of cats or the one bullet in the I pipe. Just thought this info might be helpful to those of you who are in the same boat I was in...Good Luck!
. I was determined to correct the rasp without cats and I wanted to keep the GMMG because I love the tone/sound and the way it's set up with my Corsa clones. The final result is a very deep exhaust that's still very loud, especially at WOT, but refined without the rasp. I had two 3" Dynomax bullets installed in the front of the Y-pipe where cats normally go (where the rear O2's are). It really cleaned it up and there are no issues with clearance, etc. I already had a Magnaflow bullet in the I pipe and it had helped a little when I was a bolt on set up but not much. It really only deepened the note.The only install issue was matching up the round bullet opening with the oval y-pipe on the driver's side. The header collector fit perfectly inside the bullet opening on one end and we made the bullet opening kinda oval and kinda rounded the y-pipe so it'd match on the other end.
So those of you with rasp may want to consider this instead of cats or the one bullet in the I pipe. Just thought this info might be helpful to those of you who are in the same boat I was in...Good Luck!
Thread Starter
TECH Apprentice
Joined: Aug 2007
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From: Mississippi
A good y pipe merge will do wonders for that. When Patrick G made his custom y pipe he went with an expensive merge and he said that is got rid of the rasp and drone. However he was using an SLP Dual Dual muffler. Hope that helps.
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You will never get rid of it. The hammering sound you refer to will move around a little depending on what combination you have, and the tone of it will be higher to lower depending on your combination but they all do it, even duals. The reason most dont know their duals have rasp is because most are dumped and it cancels it out pretty much. Take a system like the TSP duals dumped and you dont hear it rasp and then extend them out the back and it will rasp like a **** around 2800rpms.
Some people just dont know what rasp is. Anyone that thinks their LS1 doesnt have it could let me drive their car and I will go straight to the spot where it rasp at.
The exhaust that I have either had or heard in person and drove that tone down the rasp the best are Hooker, Magnaflow, and the Dual/Dual.
Some people just dont know what rasp is. Anyone that thinks their LS1 doesnt have it could let me drive their car and I will go straight to the spot where it rasp at.
The exhaust that I have either had or heard in person and drove that tone down the rasp the best are Hooker, Magnaflow, and the Dual/Dual.
5 mufflers right? ... 2 mufflers on the Y, 1 on the I, and 2 in the GMMG. Why not just put hi flow cats on it with the GMMG? With all those mufflers thats got to be a 150 lb exhaust system so any tiny Hp gain you get from running all those mufflers vs 2 hi flow cats is completely negated by the weight. Seems silly to put all those HP mods on the car then add and exhaust that will cause you loose 2 tenths in the 1/4 because of the weight.
Last edited by sixvi6-camaro; May 31, 2008 at 07:23 PM.
Thread Starter
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From: Mississippi
5 mufflers right? ... 2 mufflers on the Y, 1 on the I, and 2 in the GMMG. Why not just put hi flow cats on it with the GMMG? With all those mufflers thats got to be a 150 lb exhaust system so any tiny Hp gain you get from running all those mufflers vs 2 hi flow cats is completely negated by the weight. Seems silly to put all those HP mods on the car then add and exhaust that will cause you loose 2 tenths in the 1/4 because of the weight.
Don't know if I'd really consider the GMMG as 2 mufflers...basically crimped straight pipes. Why not 2 hi flow cats, because every muffler shop I've spoken with has assured me that cats will restrict my setup. They also have insisted that hi flow cats have the same core as any other cat... Thread Starter
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Ya'll are all missing my point with this thread. I know a true dual with dumps would be lighter. I didn't want duals with dumps. I wanted a cat back with tips. I wanted to keep my gmmg and I didn't want cats...period. My only options for modding were either in the y-pipe or the i-pipe. I had already put a bullet in the i-pipe so that kinda narrowed it down. Those bullets are not any larger in size or weight than a set of cats so all I have additional in weight is the magnaflow bullet in the i-pipe. I don't like rasp.
I made up my mind that if I had to run the I-pipe through the *** of a 700lb gorilla and tie strap him under the car to kill the rasp, then that's what was gonna happen.
My whole point in this thread is to let those who are not interested in true duals with dumps or running cats know that there is another option. I also stated early on, I believe, that you could probably even get away with not running the bullet in the I-pipe with this setup. This is for those with Lt's, Ory, and a cat back who are always asking questions on how to solve rasp and always get the answer to use cats. I'm simply telling them that before I'd put on cats or even put a bullet in the i-pipe, I'd put two in the y-pipe and be done. You'll never have to worry about the cats breaking up and clogging the system and it's 3" id wide open all the way through.
Critique it how you want, there's always something to find I guess. But, I have no rasp so I accomplished my goal.
I am with the OP on embarrassing... It is embarrassing. Sounds like your car is having problems running right when you have rasp. FE blocks normally cure a good amount of rasp as well, but that is only because of the resonance that AL blocks already have due to material used.
