GMMG CAT BACK Decibal level??

i want to purchase a gmmg catback system on my bone stock z28. I will have the stock manifolds,and y pipe, just the cat back will be changed. How many more decibels approximatley will this be over stock at idle and WOT. i love the sound of gmmg but i want the noise level to be as near as stock as possible? Any suggestions?

i want to purchase a gmmg catback system on my bone stock z28. I will have the stock manifolds,and y pipe, just the cat back will be changed. How many more decibels approximatley will this be over stock at idle and WOT. i love the sound of gmmg but i want the noise level to be as near as stock as possible? Any suggestions?
its noticeably louder

ull never have this exhaust close to stock

keeping the manifolds willl help tho

u dont really hear it during part throttle or cruising, but once u open up it will be much louder than stock and sounds sooo much better

headers will change everything and its soo much better

if ur looking to not have a loud car just stay stock and do no upgrades

What year is your Z28?

It sounds different on the LT1 cars than it does on the LS1's, but you didn't tell us which one you have.

Why not add a "signature" with the basic info about your car.... year, tranny type, major mods, etc. That will increase your chances of getting accurate responses.

Being that you have a pretty much stock exaust, its not going to be that bad. But if and when you get headers and decide not to have a cat it gets real loud. Most people that I know who have them put a resonator in the I-pipe to cut down on the drone at part throttle. But other than that its pretty aswome sounding system.

What year is your Z28?

It sounds different on the LT1 cars than it does on the LS1's, but you didn't tell us which one you have.

Why not add a "signature" with the basic info about your car.... year, tranny type, major mods, etc. That will increase your chances of getting accurate responses.


The z28 is a 1998, LS1 equipped, so do you guys think gmmg is worth it, anyone know if they ship to Canada??

I love mine not loud when driving around easy, but just step on the gas and its hard not to step on the gas:D GMMG:bow:

I dont think it's worth it. The cost is just crazy for a simple exhaust. That's my opinion.

Sound good? Yes
Too much money? Yes

How about flow wise is it a high flowing exhaust??

i've seen people say it dynos 3 less hp then open cutout, so yes

Wouldn't trade mine for another

I think it is worth it.

I was told it's about $225 to ship it to Canada by UPS ground. UPS will add another $60 in charges on top of that. It's free shipping if you live in the US. I'd recommend shipping it to a friend south of the border.

Assuming you ship it to your door, you're looking at about $1200 for the standard setup and $1400 for the oval tips setup.

Is their any other systems out their that are cheaper and sound close to gmmg with no rasp and isnt as loud??

i've seen people say it dynos 3 less hp then open cutout, so yes

Wouldn't trade mine for another
That 3hp couldve been caused by 50 million things.


Anyways I plan on making my own version. There is no way I would pay what theyre asking. It's insane.

It's never gonna be anywhere near stock sound levels...


Here's a video I made for people that were sending me PMs wanting to hear the car in various situations:

http://videos.camaroz28.com/search/GMMG/0/wm/048d5c0c-2cd8-4799-bca8-8e8b1b3dd6c6.htm


Oh and Gord, I still owe you those pics of the exhaust, sorry :o

It's never gonna be anywhere near stock sound levels...


Here's a video I made for people that were sending me PMs wanting to hear the car in various situations:

http://videos.camaroz28.com/search/GMMG/0/wm/048d5c0c-2cd8-4799-bca8-8e8b1b3dd6c6.htm


Oh and Gord, I still owe you those pics of the exhaust, sorry :o
nice i love the way it sounds

im running LTs and no cats so obvioulsy mines louder and the tone is slightly dif but either way it still sounds amazing , love it and always will.

sound and quality are top notch , price is a little out there. but if u want the best u have to pay(most of the time).

nice i love the way it sounds

im running LTs and no cats so obvioulsy mines louder and the tone is slightly dif but either way it still sounds amazing , love it and always will.

sound and quality are top notch , price is a little out there. but if u want the best u have to pay(most of the time).
:cool: Thanks. I'd love to have been able to run a LT/no cat setup. Still a possibility in the future. Especially once my heads/cam 383 is in. :yes:

I actually think I'm going to go get an off road pipe flanged so I can swap the cat on and off. I really want to see how loud I can get. :D

I dunno about the no cat GMMG combo. I've asked a few people about this setup and seems about 80% of them say they prefer the GMMG with the cat. One took the cat off and put it back on 2 days later and said he would never go back to no cat. That it lost it's trademark sound.

Seems it was built to be used with a catalytic converter and retains that smooth refined (but still loud and healthy) tone. Without the cat, it gets the loud pops and blats (since it's basically no muffler)

I can't personally vouch for this. But I figure it's sort of like the Loudmouth in that it sounds good stock but sounds like a tin can and a marble with LT's, no cats. Using the various sound demos, it seems to me the smoothest sounding ones are the stock car with catback setups. While the super modded cars with open exhausts don't sound as good with it.

I wish someone would post up a clip of GMMG, longtubes and no cat since that is the setup I plan on going with. :cool:

To the original poster. Here are some decibel figures I took with the system on a 3rd gen solid roof.

Stock manifolds and Y-pipe, no cat, Flowmaster American Thunder.
Idle 72 dB
70 mph 80 dB
WOT 88 dB

Idle is a cold start inside the garage. 70 mph is in O/D. WOT is measured at 5000 RPM under load. "A" weighted dB scale used. All are done inside the car with the windows closed, radio off, A/C set to OFF.

Stock manifolds and Y-pipe, Catco cat, GMMG with oval tips.
Idle 73 dB
70 mph 78-80 dB
WOT 90 dB

Outside testing goes as such:

Car idling in park, outside, fully warmed up, closed loop. Decibel reader at waist level.

5 ft away: 92 dbC or 77 dbA
10 ft away: 88 dbC

"Assuming you ship it to your door, you're looking at about $1200 for the standard setup and $1400 for the oval tips setup."

^^^ I wound up spending $1500 for the oval setup on a group purchase! The people at GMMG didn't even send me all the parts either.

http://www.lt1engine.com/media/music_page.php?song_id=47
http://www.lt1engine.com/media/music_page.php?song_id=49


here is a video of my car...hookers, no cats, gmmg...383 solid roller with a huge cam eheh :p

I dunno about the no cat GMMG combo. I've asked a few people about this setup and seems about 80% of them say they prefer the GMMG with the cat. One took the cat off and put it back on 2 days later and said he would never go back to no cat. That it lost it's trademark sound.

Seems it was built to be used with a catalytic converter and retains that smooth refined (but still loud and healthy) tone. Without the cat, it gets the loud pops and blats (since it's basically no muffler)

I can't personally vouch for this. But I figure it's sort of like the Loudmouth in that it sounds good stock but sounds like a tin can and a marble with LT's, no cats. Using the various sound demos, it seems to me the smoothest sounding ones are the stock car with catback setups. While the super modded cars with open exhausts don't sound as good with it.i agree with u. It sounds amazing without cats but with cats the sound is pure sex :)

next year im going with highflow cats. I ran out of money this year