To x-pipe or not to x-pipe - Pontiac G8 Forum: G8 Forums -
Exhaust Tech Headers, Catbacks, Mufflers, lack of mufflers

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post #1 of 8 (permalink) Old 07-27-2016, 08:41 AM Thread Starter
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To x-pipe or not to x-pipe

Alright, so I recently installed kooks midlength 1 7/8 headers/cats and I was sort of disappointed with the sound I gained. Its growing on me but its not as loud and mean sounding as I thought it would be... I'm thinking of installing an x-pipe to gain some sound but I don't want it to be obnoxiously loud to the point where cops will be ticketing me constantly... If I were to get an X-pipe what would be my best bet.. to remove the midmuff or the resonators or both?

Right now I've just got the headers and solo axlebacks, so its not quiet under a little throttle, but idle/cruising are lack luster... And lastly am I missing out on any HP by having the midmuff an reso's on?

I used the search function too btw incase anyone wants to throw that out to me lol

2009 SBM G8 GT - Solo axle-back, Kooks 1 7/8 mid-length headers/cats, VMS Tune, Volant CAI, Staggered 19" Avant Garde M310's
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post #2 of 8 (permalink) Old 07-27-2016, 10:28 AM
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Well you have definitely increased your flow by adding the mids and high-flow cats including the solo axle-backs, but your stock midsection is choking you down a bit in both flow and sound, maybe losing a handful of HP. The kink-pipe just after the stock mid-muffler goes down to just 1.75" IIRC. At the end of the mid-pipe where the flanges meet with the mufflers, that flex section chokes down to 1.75" or 2", don't remember specifically.

I'm assuming you want to keep your Solo a/b's so what I would suggest is getting the mid muffler and resonators deleted and adding the Magnaflow 12468 muffler. It is an X-pipe internally within the muffler housing with sound absorption materials, so you get all of the benefits of an X-pipe with some noise management also. I think a lot of people are running this setup or something similar since I remember reading through a lot of exhaust threads stating that a regular X-pipe with headers and Solo's were too loud and obnoxious for some.

Someone else should chime in with some info and personal experience with it. Shop for price on these mufflers, they really are worth the money, all stainless construction, quality stuff. Hope this helps!

2008 White Hot GT w/ Premium Pkg. 185k miles and counting!
Blueline Performance DoD delete deluxe pkg w/ "The Probationary" Cam, Pypes Headers, Spectre Intake, ZL1 fuel pump

Tuned by Bob at Next Gen Built Performance

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post #3 of 8 (permalink) Old 07-27-2016, 11:17 AM Thread Starter
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Yeah, thanks a lot definitely helps, but I agree i'd love some input from someone with personal experience

2009 SBM G8 GT - Solo axle-back, Kooks 1 7/8 mid-length headers/cats, VMS Tune, Volant CAI, Staggered 19" Avant Garde M310's
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post #4 of 8 (permalink) Old 07-27-2016, 02:27 PM
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With those headers you will never be happy cutting up the stock exhaust. I did it a few years ago. X-pipe, gutted mufflers, Turbo mufflers. Then Solo used my car to measure up the 3" exhaust.
I took the solo Mach balanced. I noticed right away that is flowed
better, made more power and sounded better than ever. Once you start making more power the 2.25" stock piping start holding you back.

'09 PBM GT. #2 Kook's Mids, Solo Mach balanced, SCT X4 Tuner. LED H/lamps, Tail lamps and Interior
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post #5 of 8 (permalink) Old 07-27-2016, 04:05 PM
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i have pypes axle backs and long tubes with no cats and recently had the mid muffler and resonators removed for an x pipe and it was obnoxious. It sounded good through most higher RPMs but had a raspy sound at certain RPMs at certain loads and it droned worse than ever.

I went back and had the magnaflow 12468 muffler added after the x pipe i added and it tamed it down significantly. It still sounds really good and aggressive from the back, but you can hear your self think inside the car now.

Eventually, i do want a straight pipe type axle back like the solos just to add a small amount off sound back to it, but with my experience, the x pipe alone is too loud inside the car. Sounded incredible at WOT though! But honestly, it still does!

09 G8 GT - LT's, catless, x-pipe, GXP axlebacks, Tune, Intake, Polished Camaros, 245/285, H&R, Brembo
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post #6 of 8 (permalink) Old 07-27-2016, 04:20 PM
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Short answer: x-pipe. In some form. Probably the Magnaflow muffler is the shortest path to what you want. OR, x-pipe and a set of stock axlebacks.
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post #7 of 8 (permalink) Old 07-27-2016, 07:01 PM
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I currently have Vararam intake, Solo Axleback, Magnaflow Xpipe (factory resonators), stock cam from an ls3 (DOD delete) with a custom local tune and Manzo headers. All done in that order one at a time (tune and headers at same time).

Each piece has added up to make it pretty loud. I think the factory resonators are keeping it toned down just a bit. (no rasp though)

After having it setup this way for a while I've decided it's just too loud for my taste overall. I love the sound at WOT but it is ridiculously loud at a cold startup. It vibrates half my house when I start the car in the garage in the morning.

I tried the stock axleback, but even with headers and Xpipe (then factory resonators), IT WAS DEAD SILENT. No burble whatsoever...

I looked at adding the Magnaflow mid muffler to help, but I've decided on Dynomax VT mufflers with SLP tips (hopefully keep the WOT sound I like, but mellow out the idle and low RPM a bit). Should be putting those on this weekend. (Then the Solo Axleback will be up for sale if I decide I like the sound of the new setup)

Last edited by 6 litre; 07-27-2016 at 07:29 PM.
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post #8 of 8 (permalink) Old 07-27-2016, 07:35 PM
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May I suggest another route?. What about cut outs?

I'm definitely loud and I am definitely quiet too lol. I get the best of both worlds. I did the x pipe, rear res. delete and cut outs at the same time and was loud even then. Im not the loidest G8 out there but loud enough. Can't wait to see how she's gonna sound after a cam, lifters and possibly heads. Waiting for the stock one to tick before I do.

Also . Wiith the kooks headers and my cut outs closed. You can still hear that kooks sizzle under the hood , so I can't say she sounds stock closed

Keep in mind that not everyone likes the same thing. What one person says or thinks sounds good, may sound bad to another person or to loud or quiet. Ive also been told to also keep in mind that what you hear on a video may not sound the same in person.

Good luck and happy modding!

Pat G tune
KOOKS 1 7/8 mids and HFC's (coated)

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