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WOT's Up Doc?
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Discussion Starter #1
I couldn't find if this was mentioned anywhere else so sorry if its a repeat.

There are flanges between the Cats and the mufflers that would allow you to remove the mufflers completely. What would be the potential gains from doing this? Any downside? And I don't mean "legal" downside.

Thanks for any help guys!
 

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Can't help ya, Sorry.
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I seem to remember a post that said they only gained 4 or 5 HP on a dyno removing the pipes. But some are claiming large gains with a Cat Back system.

I'm running long tube headers from Stainless Works and the stock catback. I went from a Dyno run of 280 RWHP stock to 331 RWHP after headers, CIA and tune.
 

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WOT's Up Doc?
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Discussion Starter #3
Headers are definately the way to go. But I was wondering about a short term solution with hopefully, a modest gain.

4-5 hp? Not much is it?
 

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Can't help ya, Sorry.
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Not much at all. I have heard many opinions on the matter though. I gained 51 HP and I kept the stock cat back. If I had a dyno that was free I would play a bit more with a freer flowing catback but people I trust tried it eariler in the year and didnt' gain a thing.

CMNT's dyno #'s are nearly identical to mine (My 331 is > his 330) (this will kill him, I chuckle to myself) and he has a slightly modified catback. There is one more I know of adding headers this week and he has had a cat back fabbed w/ 2.5 pipes all the way back. If he gives up his dyno numbers we will have a good comparision.
 

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13 year owner
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It doesn't kill me. Some cars are simply stronger than others.

While you can simply unbolt the catback, it is a completely straight pipe setup even with the stock mufflers. So it really isn't too restrictive in terms of blockage.

The only difference in my Magnaflow's vs. the stock mufflers is A) the tube inside the stock mufflers is slightly curved vs. the Magnaflow's that are straight on an angle from inlet to outlet and B) Sound. The Mag's have a better tone to them at idle and are crisp at WOT.

What hold up our system is the size of the tubing used. It's 2.25" into the muffler and 2" out.

No exhaust mods AFTER the catalytic converters affect emissions. After the post cat O2 sensor, everything is purely noise abatement.
 

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Captain Thread Killer returns
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sxty8goats said:
I'm running long tube headers from Stainless Works and the stock catback. I went from a Dyno run of 280 RWHP stock to 331 RWHP after headers, CIA and tune.
Did this change the stock exhaust sound much? louder? better? worse? I am partial to the stock sound
 

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13 year owner
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Did you not hear my dyno video posted here?

BIG difference. Ask anyone who's heard mine.
 

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Captain Thread Killer returns
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CMNTMXR57 said:
Did you not hear my dyno video posted here?

BIG difference. Ask anyone who's heard mine.
uh no I must have missed that....where is it?
 

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13 year owner
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Do a search in this forum for a thread labeld "CMNT's dyno with Video" or something like that. It was posted around 6/29. It has a little tinniness in it, but you can still hear it at WOT on Speed's dyno.
 

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Can't help ya, Sorry.
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Bigger better louder more. Huge change in sound. I kind of like the header w/ stock catback tone. I think I'm slightly quieter than CMNT but that may be lack of perspective. I'm inside my car and out side his... We will get to gather soon and let yall' know.
 

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I heard another GTO last night w/ headers, 2.5 pipes back to Cherry Bomb's. It had one of the sweetest idles I have heard on an 04 but at WOT it is loud as all hades opening up on a bad episode of Buffy. Sounded great but it Loud is not your thing, stay away from the Cherry Bomb style "mufflers".

I actualy would like to quiet mine down a bit. Does anyone know of a Muffler that will mute the sound w/out causing an excessive amount of back preasure?
 

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13 year owner
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Yea, the Magnaflow's :D

Mine to me is too quiet inside the car also.
 

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Feynman fan
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sxty8goats said:
I actualy would like to quiet mine down a bit. Does anyone know of a Muffler that will mute the sound w/out causing an excessive amount of back preasure?
This has been my contention from Day 1, 68! I absolutely love the sound of my GTO - with the basso profundo rumble, the gurgles, pops and crackles on lift, etc. - I just wish there was a little less of it! I'm not a kid anymore (on the outside, at least) and I get a bit more attention than I'd like...
 

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Mine sounds great inside the car, But I feel it is a Tad too loud at WOT @ town... :D
 

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13 year owner
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The stock one is still too quiet due to the fact that it has to meet noise level requirements as well as performance. If you like it fine, the set of Magnaflow's simply enhance the stock system without being obnoxiously loud. It is not loud like an F-Body running an SLP Loudmouth/DynoMouth or running a cutout.

It adds a deeper, richer tone at idle and then gives you more crisp basso profoundo under throttle. It is far from loud.

Even with my headers, I wish it were a "tad" louder. Not much, just a tad. Enough to make small imports scared. Right now, they're still questioning what's under the hood. I guess this can be a good thing too.

You wanna hear loud, I'll take you for a ride in the Camaro. The GTO even with the headers is like a Caddy in comparison.
 

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Feynman fan
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Same here, 68. I live in an historic district with on-street parking and houses very close together (within arm's-reach, in some cases) and with small set-backs (read: little front yards.) Old houses, lots of windows, close to the street - I don't want to be a neighborhood nuisance...
 

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Can't help ya, Sorry.
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gto_in_nc said:
This has been my contention from Day 1, 68! I absolutely love the sound of my GTO - with the basso profundo rumble, the gurgles, pops and crackles on lift, etc. - I just wish there was a little less of it! I'm not a kid anymore (on the outside, at least) and I get a bit more attention than I'd like...
You missed a bit here. I have Headers and they tripple the volume of the car. I just want to tone that back a bit. I like rumble and roar. I want to be about 2x louder than stock.

Or I want a silent car w/ 500 + HP. Sleeper style.
 

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13 year owner
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Oh that's just like most of the neighborhoods in the city!.
 
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