mph476

iTrader: (7)

alright guys help me out...i finally got my gmmg exhaust installed and now i'm debating on Long tubes strictly for performance gains...i say that b/c right now i pretty much have a stock setup other than exhaust and a lid... and i love the way it sounds...my question is how much do LTs change the sound of the gmmg exhaust? I'm using it as a daily driver so keep that in mind...thanks guys

LS1_Disciple

iTrader: (1)

If you don't like rasp, you'll definitely want to stick with a catted y with the GMMG. I'ver heard an ORY will rasp like crazy, so I went with cats on mine. I don't think it changed the sound all that much. If anything, it's what I would call deeper, not necessarily louder. I (and my wife) thought the GMMG on stock manifolds had a drone around 2-2.5k. Now with the LTs, all the drone is gone (and wife agrees).

gettinthere

iTrader: (3)

He pretty much hit the nail on the head. It gained a little more bark at start-up and at WOT I think. The catted Y is a must though. Check out my post in the exhaust review thread stickied up top.

Scotty-Z

iTrader: (5)

If you don't want it unGodly loud and with so much rasp and drone that your ears will bleed, just get a catted Y. Since it is your daily driver, this is pretty much your only option.

2000TransAmWS6

iTrader: (12)

when one of my friends had LTs with highflow cats along with his GMMG it sounded really deep, like a classic muscle car.

now that he's taken the cats out its not overly raspy, and i'm not sure why , because i've heard other GMMGs with no cats that were extremely raspy.

FenixSS

iTrader: (3)

are there sound clips somewhere of GMMG with ORY and of GMMG with Catted Y?

LS1_Disciple

iTrader: (1)

I forgot about start up - gettinthere's right. Definitely more "bark" on the first start of the day or if it's been off for a while. Almost like a small explosion. But then it settles down pretty quick.

Still no complaints from the neighbors, even when I leave at 6:00AM.

Oh, and www.ls1sounds.com has a lot of different combinations. You may find a comparison there.

2000LS1Z28

Well I went from the GMMG only (stock manifolds, cats, & Y-pipe) to the GMMG with Kooks LT headers w/ their highflow catted Y set-up and here is what I honestly think:

Start-up is louder like the other guys said. Always sounds great when I turn the key!

Idle is about the same (maybe a little clearer).

Acceleration is similar until you go over 2k rpms and damn, it just gets really deep and mean. I can best describe it as a very aggressive snarl. Awesome rumble IMO.

And WOT is definitely a lot louder in the higher rpms! Just this classic muscle car sound that stays deep and clean all the way to redline. It's LOUD IMO, but sounds downright vicious.

So I thought just the GMMG cat-back sounded good until I had the LT headers/highflow cats put on. They definitely changed the tone of the GMMG a lot (exactly as I described). I honestly like this set-up better than any other system I've ever heard on the LS1, including true duals. I wouldn't change a thing in terms of how my car now sounds (except for the cam I'll be adding sometime the future!).

The LT headers/highflow cats are WELL worth it no doubt. Absolutely NO rasp or drone either. However, without the cats, the GMMG doesn't sound nearly as good because of the rasp, popping, and more unrefined tone...

LS1_Disciple

iTrader: (1)

Another good thing I've noticed about this set-up is the GMMG retains it's same sound quality over the entire powerband. Make no mistake, it is LOUD at WOT, but not in a nasty, raspy, high-pitched way. It maintains the "mellow" tone all the way to redline. It just gets louder.

I'm with 2000LS1Z28, I like it better now with the LTs and cats than before.

ss rally red

iTrader: (8)

I work with a guy with a GMMG exhaust with Kook's LT's no cats, it is loud enough that he is looking to add a catted Y pipe.