john97z28

Does anyone know what the @ rear wheel horsepower gain is for a GMMG exhaust. Has anyone dyno'ed a car after installing the exhaust. Just curious.

1msfyter

SLP claims 25hp with the Loudmouth exhaust. So the GMMG is right up there with it ,because it flows so well. So realistically half that.

john97z28

I have "what's left" of a loudmouth due to a minor accident. I'm debating on either a Corsa or GMMG. Corsa claims that their system adds 14 dyno proven HP. GMMG has no muffler to restrict flow like the Corsa, but with a deep throaty tone.

importeater

The loudmouth doesnt have a muffler, its a resinator, basically a bugle in the pipe but there is nothing in it at all. I cant imagine anything flowing better besides a stright pipe. I've never seen the design of the GMMG but I have heard it and it sounds exactly like a loudmouth, so im guessing its the same setup just there own version.

john97z28

www.gmmginc.net

look under exhaust systems.

Bersaglieri

Hmm, I heard both and the GMMG does not sound anything like the Loudmouth. Plus I own one of the two also. The GMMG is nothing at all like a Loud mouth, let that be known first. The "mufflers" used in a GMMG are not any type of resonator, nor are they mounted on the I-pipe. The tubes you might call the "mufflers" on GMMG are nothing more than straight pipes with small raised dipples on the walls. The GMMG represents a older deep muscle car sound using similar mufflers as used in the 1960's. The system was created, tuned, and tested by one man and is made in house at GMMG. This catback as you can see is used in many of the latest GM Super F-Body's. The Loudmouth and the GMMG are by far uncomparable. I spoke with a GMMG Tech and he assured me that using a cutout with their catback would net minimal gains, such as shown in testing with a big block F-body. As far as Corsa's 14 hp quote, the HP is quotes isnt even seen until high RPMS, and 14 isnt met until about 5-6 grand. So, your seeing little to know gain until the 4-6 grand RPM range. This is not impressive to me, not to mention it is ON AN LS1, NOT AN LT1. Do Not Expect Your Highend to even come close to that of an LS1. If you are going to make a decision solely on HP and TQ numbers, go get a B&B TriFlow. They quote 17hp and 42 ft/lbs TQ. I bought GMMG because I wanted the most straight thru exhaust, with a unique design, unsurpassed sound and tone, with great power gains. And that is what I got. If you want to know more about GMMG, just call, they have a LT1 specialist on staff. They are very willing to assist you. Go with GMMG and you wont be dissapointed. Plus your car will sound like a Muscle Car not a Sports Car.

Here are some good links:

http://web.camaross.com/forums/showt...hreadid=231446

http://web.camaross.com/forums/showt...hreadid=233757

http://web.camaross.com/forums/showt...hreadid=226936

http://web.camaross.com/forums/showt...hreadid=221456

Here is my review on the GMMG:

I bought my GMMG chambered exhaust for $500 used from a Texan LS1 owner. I got my it installed and custom fitted a few weeks before I put my car in for winter. My friend's father Dale used to run his own body shop and now just does work on the side for friends, so he helped me install it. The I-Pipe I recieved from the previous owner was all fugged up (mutiple poor welds), so we tossed it and he just welded the assembly on from just after where the I-Pipe curves to make it over the axle. I figure minimal loss using the stock pipe since it is stainless steel and only a 1/4 smaller diamter anyways. He fabricated the new hangers from the ones we cut off the stock exhaust, since the LS1 hangers do not fit correctly. All said and done he just pried the thing to get the tips even and poof, a badass flowing and sounding catback. GMMG offered to sell me a LS1 to LT1 conversion kit for <$20. They also offered to sell me an I-Pipe, but as it turned out, I needed neither.

So, now my car has attitude, how about performance? HELL YEA performance!!! I felt....and yes, I do have a detailed working central nervous system, as most humans do, that allows my body to feel changes in my environment, so don't give me any bullpucky about not being able to feel a gain...anyways...I felt a very noticable differnce in power through all rpm's. The bowtie beast just pulled harded whenever pressure was applied to the gas pedal. I was quoted a 12-16 rwhp gain estimate from a GMMG techie with my otherwise stock platform and I definately felt it. He also noted that in one instance a GMMG owner tried using a cut-out with the catback on a "drag utilized modded big-block" and got decimal dyno gains. Free flowing for damn sure, it basically uses hollow pipes with small dimples for a "muffler."

Now the sound of this catback...well it sounds good like hooker and borla....WRONG it sounds incredible many times better than others, a consitant deep rumble at idle and a mean commanding hellaish scream at "extreme acceleration." It keeps deep and mean tone all of the time. You cannot even fathom the greatness of this exhaust's sound unless you've hear it in person. I figured it would sound pretty good considering the clips I had heard, but in person, it is unreal, simply unsurpassed. The tone at driving RPM from 1500-3500 is perfect for crusing even on a highway, just a tap on the gas and the 350 roars to life.

Oh yea, and it looks sweet too, I have the oval tips which are unique and really compliment the rear of the car nicely. The crossover piping is unique only to this system, very impressive. Great overall system made of quality materials and engineered flawlessly. I would highly recommend this catback to anyone who is interested an awesome exhaust tone and seat-of-the-pants performance. I'll have a website with pics up sometime soon. Yes I have video clips with sound, none from my Z yet, but several from other LT1's and LS1's. Here is GMMG's site for more information, enjoy the custom cars as well as the chambered exhaust. http://www.gmmginc.net/

-Dustin-

john97z28

I know the Loudmouth and GMMG are totally different sounds. I was thinking of Corsa since a have a friend who works as a parts manager for GM an can get a great deal on one. I've heard Corsa on an LT1 on their site and it sounds similar to the Loudmouth, high pitched and raspy.

I never heard a GMMG in person (have heard sound clips) but searching posts I never saw anyone say anything bad about it, other than the price. There was a group purchase on an other message board and I'm pissed that I missed it, $775 for the system shipped + oval tips. I'd buy it in a second if another one comes around like that. I can't justify paying $850 for something that I know I can get for $775. Seeing that I have spent over $2000 so far in parts (McLeod street twin, LT4 heads, intake, Comp R's, XE cam, etc) for my car since last year, and I'm expecting to spend another $4000 this spring (forged crank, rods, pistons, supercharger, twin intercoolers, exhaust, etc.) every dollar I save counts.

Bersaglieri

Used systems run $500, I fitted an LS1 version on my 94 Z. Any of the GMMG catbacks cam be fitted onto any 82-02 car, the only difference is the I-pipe and hangers..my guy fabbed the stock hangers to fit the GMMG and we cut the I-pipe to fit. Good luck with the catback.

-Dustin-

DrivinSidewayz

corsas muffler is a strait through pipe, with just little slits at the end of the muffler to allow sound waves through. and when i put my corsa on my stock lt1, i gained torque off idle, wasnt just high rpm

Bersaglieri

I would like you to show me how a crossflow muffler is a straight thru pipe. I see they call it a straight thru design..but its not a straight thru pipe, epsecially on the F-body crossflow application.

Also I just didnt mention the TQ gains, there are some on their site also, I didnt say there was only HP to be gained. The Dyno Graph on Corsa's site shows a peak TQ gain of 9 ft/lbs and only shows gains from 3250 and up. Mind you THIS IS ON AN LS1, NOT an LT1, I'd expect less HP/TQ on an LT1. If you are a dyno man then get a B&B which says you'll get at least 42ft/lbs and 17hp. But for muscle car sound and performance get a GMMG.

-Dustin-

Bersaglieri

Oh and as far as the original question, GMMG quoted me somewhere from 12-18 rwhp depending on my setup. Much more if I had Heads and Cam or a Power Adder.

-Dustin-

DrivinSidewayz

lmao you tool, unlike you i dont go based on solely what you hear online, i noticed actual gains of torque off idle(meaning the car in the real world), i didnt dyno it, ive never dynoed my car, and true the muffler isnt an actual strait pipe, there is a bend inside the muffler

2002LS1Z28

I gained exactly 26.5rwhp & 26rwtq (SAE corrected) on the same dynojet chassis immediately after the installation of a Direct-Flo lid and the GMMG cat-back system on my LS1. Since an intake lid has consistently been proven to be worth anywhere from 8-12rwhp on the dyno, obviously I gained quite a bit through the GMMG. You decide though how much the GMMG was really worth...

Dude, go with the GMMG if you want that deep, meana$$ muscle car sound. Or Corsa if you're looking for a quieter, high-pitched more sports car-like tone.

BTW, a GMMG may sound similar to a Loudmouth at idle and down low, but it sounds absolutely nothing like it throughout the rest of the rpm range. WOT is totally different (GMMG sounds just plain DEEP up top with no rasp). I love that old school muscle car rumble at WOT of the GMMG!

Mike

Bersaglieri

I am a tool because I quoted a manufacturers dyno graph. Seems like a fair assesment. I have never based my comments and opinions solely using online information only. I am only stating what "The Dyno Graph on Corsa's site shows.." I didnt say you didnt feel gains, hell I never dyno'ed my car but after the GMMG I felt gains everywhere in the RPM, that was real life too. Your comments to my posts have shown me that you are taking what I am saying in the wrong way and even somewhat personally. Peace out man, we are on the same team

Thanks for the info 2002LS1Z28.

-Dustin-