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Thread: Same old tired question about exhausts

  1. #1
    Junior Member
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    Default Same old tired question about exhausts

    My car is not built but I wanted just some more sound out of it. Read so much about exhaust on here and determined a good setup with zero drone is the GXP axlebacks, with the GT midpipe modified to eliminate the mid-muffler and resonators replaced with X-pipe.
    I waited to find a deal and recently found one, which was axlebacks and the GXP midpipe for one price. Picked up some new gaskets online to get things ready.
    I had fun for a few days with the GT AB removed (people stared). It did drone in the 1200rpm range but it wasn't all that bad, however I could foresee that being miserable on long drives.
    I put the GXP AB on it (with stock GT mid) for a few days to get rid of the unwanted attention, just used a bead of black RTV as a temporary seal. I could hear a little rumble out of the back of the car but nothing crazy, still shockingly quiet, and could barely hear the 4-8 transition but both modes were quiet with a some popping upon decel;. A little more noticeable idle when standing behind the car, the biggest difference was hearing it with remote start, a noticeable bark at startup.
    Update to this week: pulled my car up on my trusty Harbor Freight plastic magnum ramps and made a late night project out of it crawling around underneath, but managed to get it done. Used Mahle gaskets (F32245 donuts in front, F32258 flanges in rear with a fresh bead of Permatex copper on both sides of flange gaskets).
    Now running stock manifolds and cats, with GXP midpipe and axlebacks.
    More noticeable bark at startup, more noticeable at idle, more noticeable inside at highway speeds, but that's about it. I have not heard it from the outside yet and I have to drive it a little more but initially my impression is - too damn quiet. I'm already preparing to sell these parts and go get a good catback, I've had my eye on the Solo for a while...

    Anyone have thoughts on comparing a stock GXP mid/AB setup to an aftermarket catback?
    Using Solo's example below, they consider "1-10 scale… 1 being stock quiet and 10 being rockin’ noisy..."
    Mach balanced: outside=4, inside=3
    Mach: outside=5, inside=3.5
    Mach shorty balanced: outside=6, inside=4
    Mach shorty: outside=7, inside=4.5
    Where does the GXP setup fall on this scale, so I can get a reference? Is it a 2? Or is it a 5? I have no clue.

    I used to be thinking I should go with their quietest setup since it seems there are so many complaints on here of the drone/resonance that happens with louder exhausts on these cars, but I have also learned there are a lot of picky people on here (like me!). Now I am thinking if (in my opinion) the GXP mid/AB combo is this quiet (to me), perhaps I should be looking at the Mach shorty balanced...
    2008 GT PBM onyx/red CLOTH
    No roof, no premium, no sport
    Just yee-haw base equipment
    Since 08/28/2012

    Some sweet Wal-Mart floor mats | Matched 18" GT spare and tool kit | Cheap rear deck soundproofing | Extended RKE antenna | Trunk liner | Tints 35% fronts/5% strip/5% rears & CHMSL flasher | Autodim mirror | WAMS Ataris | Costar Bluestar | red leather shift knob | Cortex | Mobil1 & PF63 | improved stock intake | UPR catch can | Full GXP mid/AB | More mods awaiting install...

  2. #2
    Administrator Chewy's Avatar
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    Default

    Stock cats and manifolds quell a lot of the sound so putting a more aggressive exhaust isn't an issue as long as it's designed to kill the drone. Corsa is my favorite, between them and Solo and the quality is 2nd to none with its 316L stainless build.

    I had a Magnaflow axle back on my GT which had the x pipe and not the newer mid muffler and you could hear the 4 cylinder mode, but it was NEVER annoying or painful. The newer mid muffler MF supposedly does away with any drone. IMO, the MF has a clean muscle car sound without the sharpness others have.

    This is my GXP with Corsa... LT's, no cats stock Corsa. NO DRONE!

    https://www.youtube.com/watch?v=aRkPgZM2fw0

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!

  3. #3
    Administrator Chewy's Avatar
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    One of it on the dyno... Keep in mind, my car is VERY modded, but again, NO DRONE!


    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!

  4. #4
    Senior Member Unavowed's Avatar
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    You need headers. Everything else changes after that. My car was so loud with ARH longtubes and catted X pipe that i bought a set of GT mufflers to run on the street. But I see you're in California, so....

  5. #5
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    Chewy...nice car but...I'm not anywhere near your level. Laughed my ass off at your video though. At 0:09 the guy on the far left was smart enough to realize something very awesome and loud was about to happen. The "tough guy" sitting down figured he didn't need to cover his ears, until the 0:14 mark he realized he had made a big mistake...

    Quote Originally Posted by Unavowed View Post
    You need headers. Everything else changes after that. My car was so loud with ARH longtubes and catted X pipe that i bought a set of GT mufflers to run on the street. But I see you're in California, so....
    Odd, you sound a lot like someone on another forum

    Perhaps I'm asking the wrong kinds of questions. It's been a while since I've seriously trolled through things on here.
    Are there any header solutions with cats capable of running without a tune? I.E. cats that actually allow the car to run clean?
    And (this is probably asking for too much) also CA legal?

    Shoot I have no idea. Things could have changed a lot over the past few years with the SS coming out and bringing the G8 aftermarket alive again.
    2008 GT PBM onyx/red CLOTH
    No roof, no premium, no sport
    Just yee-haw base equipment
    Since 08/28/2012

    Some sweet Wal-Mart floor mats | Matched 18" GT spare and tool kit | Cheap rear deck soundproofing | Extended RKE antenna | Trunk liner | Tints 35% fronts/5% strip/5% rears & CHMSL flasher | Autodim mirror | WAMS Ataris | Costar Bluestar | red leather shift knob | Cortex | Mobil1 & PF63 | improved stock intake | UPR catch can | Full GXP mid/AB | More mods awaiting install...

  6. #6
    Senior Member Unavowed's Avatar
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    If you just want sound, get yourself some SLP loudmouths. Mine were custom made in 3" mandrel bent 304. They are embarrassingly loud to drive on the street for me, but maybe on a stock car with stock manifolds and mid-muffler they may not be that bad. And yes, my cut and paste skills are strong...

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