Which catback to run with LT's
Thread Starter
Staging Lane
Joined: Jun 2008
Posts: 70
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From: London, UK
Which catback to run with LT's Guys, I had a set of American Racing LT's with catted y-pipe fitted a couple of days ago to my 2001 Z28, which was otherwise stock apart from having a GMMG catback. The install went well but, as I knew might be the case, I'm now getting plenty of rasp whenever I accelerate and it's really loud - too much so for my liking. At first I thought the system might be leaking somewhere but the guys who responded to my other thread confirmed that it is normal for a GMMG / LT combo to sound this way. 5 minutes under my car with a wrench confirmed everything was tight.
There's no way I'm going to enjoy driving around with it like this so I'm planning to fit a different catback to try and eliminate the rasp and quieten things down a little. The most common solution discussed on here seems to be Magnaflow, but I'm not sure what other options there are out there that come in stainless steel. What other catbacks should I be considering and how would they be likely to rank in tone/volume against the GMMG and Magnaflow?
There's no way I'm going to enjoy driving around with it like this so I'm planning to fit a different catback to try and eliminate the rasp and quieten things down a little. The most common solution discussed on here seems to be Magnaflow, but I'm not sure what other options there are out there that come in stainless steel. What other catbacks should I be considering and how would they be likely to rank in tone/volume against the GMMG and Magnaflow?
TECH Enthusiast
Joined: Feb 2007
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From: chicago
I would have thought LT's catted Y and GMMG would have made the best sounding stock internal LS1. I have GMMG catback on my camaro and its not loud enough. Excellent tone though with stock cats and manifolds
There have been plenty of guys that throw a bullet in the I-pipe to tone it down after LTs. You could give that a try and see if that does the trick for you
I wouldn't change catbacks.
There have been plenty of guys that throw a bullet in the I-pipe to tone it down after LTs. You could give that a try and see if that does the trick for you
I wouldn't change catbacks.
Thread Starter
Staging Lane
Joined: Jun 2008
Posts: 70
Likes: 0
From: London, UK
Okay, thanks for the quick replies. I've heard this thing about installing a bullet in the I-pipe before but, to be honest, I haven't got a clue what that is all about. Is it a case of cutting the I-pipe and basically installing an additional muffler?
Is it something like this....
http://www.magnaflow.com/02product/s...e=main&id=8536
Is it something like this....
http://www.magnaflow.com/02product/s...e=main&id=8536
Last edited by yabadaba; Jul 3, 2010 at 02:19 AM.
Duals. Problem solved. NO RASP AT ALL.
You could probably sell your GMMG/y-pipe for some good money and use it to buy either the TSP or LPP duals.
Here are videos of my car with LPP LT and LPP duals.
http://www.youtube.com/watch?v=uvnBKqWAlHY
http://www.youtube.com/watch?v=N6fPQ...eature=related
You could probably sell your GMMG/y-pipe for some good money and use it to buy either the TSP or LPP duals.
Here are videos of my car with LPP LT and LPP duals.
http://www.youtube.com/watch?v=uvnBKqWAlHY
http://www.youtube.com/watch?v=N6fPQ...eature=related
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i have a magnaflow catback and thought about ditching it for a GMMG or possibly tru duals with sweet thunders..
the magnaflow sounds great, good quality, but its not really loud. i have longtubes, and a 230 cam and its pretty quiet.
the magnaflow sounds great, good quality, but its not really loud. i have longtubes, and a 230 cam and its pretty quiet. LS1 Tech Stories
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I personally think GMMG is the best sounding exhaust for f bodys, I have lt's, no cats, with gmmg and it sounds amazing, though my y pipe is 4 inch with an electric cutout so it may sound deeper than what yours does. I would keep the catback and put another resonator in the i pipe somewhere before selling it. but if you sell it you can get some good money for it im sure
Thread Starter
Staging Lane
Joined: Jun 2008
Posts: 70
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From: London, UK
That true dual setup that Aetos posted the videos of sounds great and I can see myself being tempted down that route at some stage in the future, but for now I'm going to stick with what I've got and try adding a bullet muffler in the i-pipe. Just not sure which one to go for. I'm thinking it's probably best to go with a smaller diameter one (4 or 5") to avoid clearance issues....maybe one from Dynatech or Magnaflow.
It looks like by the end of the summer I will be buying the lpp true dual setup! It sounds good and looks good under there. I wonder how much weight you could loose by do headers and lpp setup. Getting rid of the cats and the cat back exhaust has to get rid of a good amount of weight wouldn't it? I mean the cats way 15 lbs and the catback ways 50.
Thread Starter
Staging Lane
Joined: Jun 2008
Posts: 70
Likes: 0
From: London, UK
Okay here's a dumb question, but given that my GMMG pipework is 3" should I be looking for a muffler that is listed as having 3" inlet and outlet or is the idea to get one size larger so that the muffler fits over the i-pipe? I'm thinking it's still the 3" inlet/outlet I need and, if so, will probably go for a Magnaflow #14419
I love my GMMG, ORY, LT's combo. It's not obnoxious but can get loud if I put my foot in it. My suggestion to the OP is to get a catted-y and it'll take a little rasp out and quiet it down. Also shift at 2k rpm's to keep it quiet until you get cats. Good luck man. 
Thread Starter
Staging Lane
Joined: Jun 2008
Posts: 70
Likes: 0
From: London, UK
It's the sudden change in tone from deep rumble to that high pitched metallic onslought that I can't take. I've seen pedestrians jump when I've put my foot down - pretty amusing at first
but this is a daily driver so I've got to get it toned down! 
11 Second Club
Joined: Dec 2002
Posts: 1,498
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From: long island, ny
gmmg with long tubes even with cats does sound raspy. it would sound even more so if you did not have cats or that awesome ARH y-pipe merge they build. in reality the cats ARH uses does not do much lol.
i have there 1 7/8 headers and ORY. i also have a magnaflow exhaust with an extra magnaflow stainless bullet in the I-pipe. NO RASP what so ever with a deep rumble at idle thats not to loud and when im on it sounds sick. i also have dual cutouts but thats a whole nothing story. i think that my setup is the best exhaust setup for a heads and cam ls1.
check here
i have there 1 7/8 headers and ORY. i also have a magnaflow exhaust with an extra magnaflow stainless bullet in the I-pipe. NO RASP what so ever with a deep rumble at idle thats not to loud and when im on it sounds sick. i also have dual cutouts but thats a whole nothing story. i think that my setup is the best exhaust setup for a heads and cam ls1.
check here
