GMMG vs. MagnaFlow
TECH Enthusiast
Joined: Feb 2003
Posts: 614
Likes: 0
From: Michigan (Holland/Grand Rapids)
Re: GMMG vs. MagnaFlow
IMO: GMMG is too loud without Cats.
I took the chance of installing the GMMG with the gutted cats as the empty cat bodies act like expansion chambers (i.e. bullets) and totally kill the rasp.
I know as I gutted the cats while I still had a Flowmaster cat back system and had ZERO rasp. You have surely read the Flowmaster is notorious for terrible rasp with removed cats, just not with the gutted ones.
Now I'm sure you would get aweful rasp with GMMG and removed cats so I would not recommend it. When I install LT headers next year I will be sure to use cats in the y-pipe to keep from having rasp.
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Re: GMMG vs. MagnaFlow I have Magnaflow with hooker lt's and no cats, it sounds great. The 224 made it even better. Stop worrying about it. These cars all sound like they idle underwater, at least when they are stock. 
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TECH Fanatic
Joined: Nov 2001
Posts: 1,098
Likes: 0
From: I-L-L-I-N-O-I-S
Re: GMMG vs. MagnaFlow You really need to hear both in person to get an idea of which system you'll like.
With that said, one(GMMG) is so much more aggressive sounding on a stock LS1 than the other(Magnaflow) and likewise on heavily modified LS1's.
Here are some clips of the GMMG cat-back on STOCK(lid only) LS1's:
www.cobraeater.cz28.com/Exhaust
And here are a couple of nice revving clips of the GMMG on lid only(Berger SS) LS1's:
www.01pewterz28.cz28.com/vids.html
GMMG's website also has a couple idling clips of this system(one car is lid only, while the 435hp WS6 has heads/cam/headers/highflow cats):
www.gmmginc.net
After hearing these clips I didn't even bother to wait until I heard this system in person(and it actually sounds even better in person believe it or not).
Mike
With that said, one(GMMG) is so much more aggressive sounding on a stock LS1 than the other(Magnaflow) and likewise on heavily modified LS1's.
Here are some clips of the GMMG cat-back on STOCK(lid only) LS1's:
www.cobraeater.cz28.com/Exhaust
And here are a couple of nice revving clips of the GMMG on lid only(Berger SS) LS1's:
www.01pewterz28.cz28.com/vids.html
GMMG's website also has a couple idling clips of this system(one car is lid only, while the 435hp WS6 has heads/cam/headers/highflow cats):
www.gmmginc.net
After hearing these clips I didn't even bother to wait until I heard this system in person(and it actually sounds even better in person believe it or not).
Mike
TECH Enthusiast
Joined: Feb 2003
Posts: 614
Likes: 0
From: Michigan (Holland/Grand Rapids)
Re: GMMG vs. MagnaFlow I heard all of those clips posted above and said to myself.....eh......not that impressed.......But when I heard my first GMMG in person I said DAMN! 
That's for me! The sound clips don't even come close to doing the sound of the GMMG justice, you must really hear one in person to understand. Until then the Magnaflow will sound good. 
That's for me! The sound clips don't even come close to doing the sound of the GMMG justice, you must really hear one in person to understand. Until then the Magnaflow will sound good. TECH Fanatic
Joined: Nov 2001
Posts: 1,098
Likes: 0
From: I-L-L-I-N-O-I-S
Re: GMMG vs. MagnaFlow Let's put it this way guys, those clips of the GMMG may not be the best, but they are definitely better than most of the other systems I've heard on the web(and I actually happen to think most of them sound damn good; they impressed me over the other "crap" I've heard).
But I'll agree that this exhaust truly does sound even better in person.
But I'll agree that this exhaust truly does sound even better in person.
Staging Lane
Joined: Jan 2003
Posts: 55
Likes: 0
From: Ottawa, Canada
Re: GMMG vs. MagnaFlow only drawback to the GMMG is the price. On the plus side, it's made of 304 stainless steel (the best), and is straight thru design so it will perform as good if not better than most catbacks.
On The Tree
Joined: Jul 2003
Posts: 110
Likes: 0
Re: GMMG vs. MagnaFlow
Magnaflow= 1/2 price, better performance and stainless steel. No comparison.
Re: GMMG vs. MagnaFlow I run a Magnaflow with an OFY and Headers. You can hear it half way across town when I jump on it. In a stock set up it has a deep rumble at idle but with no cats its to loud. Imagine how bad the GMMG would be with my set up.
TECH Resident
Joined: Jul 2002
Posts: 958
Likes: 0
From: Mentor, Ohio
Re: GMMG vs. MagnaFlow I am considering dumping my SLP loudmouth off my SS and putting it on my ws6 since it still has cats. Then I am getting a SLP dual dual for my SS. The SLP PERFORMANCE PARTS DUAL DUAL sounds SAWEEEET without cats, nice deep and little to no rasp. I seen a car with FLPs, no cats, SLP dual dual and a bullet muffler in the intermediate pipe and an electric QTP cutout just after the bullet and dual electric cutouts in the y-pipe. He had 3 different exhaust tones at the push of a button.
