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Old 02-14-2006, 10:48 PM   #1
hikeeba
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Default OEM muffler gutting project - 02 WRX

This is just an FYI.

So I'm gutting my OEM muffler - I get this far and I found this:


I've seen the inside of an 02 WRX muffler before and noticed the bulged section of the tailpipes. I did not realize that the bulged section was an inner perforated with some sort of dirty cotton candy material wrapped around it, and then overwrapped with another section of steel pipe. Had I known that, I may have tried to carefully remove the outer bulge and cotton candy, and left the perforated sections in place. Oh well, I thought that was interesting.
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Old 02-14-2006, 11:47 PM   #2
99subi
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yea its muffler pack, i used it on my YZ250 to tone the stock exhuast down a lil bit, my guess is thats why they used it too
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Old 02-15-2006, 08:30 AM   #3
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Good luck with this. The last guy that did this and posted about it was less then impressed with tht e sound.
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Old 02-15-2006, 09:15 AM   #4
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Yea J-Rex2004, I saw that post/thread. We'll see how it turns out. I don't really have any expectations for this project, other than to finish it and seal it up without welding. I'm hoping for a different sound than stock, but based on the fact that I am going in and hacking things up and such, I am not expecting 'teh awesomest' sound.

It has been insteresting and fun so far.
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Old 02-15-2006, 09:31 AM   #5
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It sounds pretty decent, other than the air-rushing sound, but it killed my car's performance once i de-catted the car. Felt fine up until I did my downpipe, then it couldn't get the air out fast enough, and the car started getting a slight midrange bucking feeling.
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Old 02-15-2006, 09:51 AM   #6
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Interesting... Air rushing sound? Hmmm... How much did you gut out? Did you remove the bulkheads? Noizemaker, if you can add any details, that'd be great. I've read about other people gutting their muffler, but no one ever goes into any detail as to what exactly they have done.
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Old 02-15-2006, 07:59 PM   #7
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I was warned before I installed it there'd be an 'air' sound. Sure enough, there was. it sounded like someone blowing across the top of a bottle. Of course, if air is going across, it can't go through, so I got bucking as backpressure came and went.

The muffler was picked up pre-gutted here on NASIOC. Since it's never going back on, I'll take the plasma cutter to it tonight, and take some pictures as I've no clue how it looks inside.
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Old 02-15-2006, 10:56 PM   #8
hikeeba
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Default Yeesh

Yea, Something sound whacked with that. You've got a plasma cutter? wow...

What I have in mind to do will make gases flow more freely through the unit. Probably not so much so as to make any hp gains, but it certainly won't be as restricted as the OEM setup. how it will sound, well, that's a crap shoot at this point. We'll see...

No progress tonight due to LOST and Olympics. A fellow Subie owner is now sitting in 2nd in men's moguls/freestyle. Woohoo!
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Old 02-15-2006, 11:11 PM   #9
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Does anyone have a link to the other thread about the muffler being hacked up and what it sounded like?
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Old 02-16-2006, 02:07 AM   #10
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Here's a couple pics I took tonight after getting medieval on the backbox with the plasma cutter, a hammer, and a prybar... I didn't realize the thing was 2 layers thick, and couldn't figure out why it wouldn't move, hence the abuse. So yeah, basically the dividers were left up, and everything else removed.


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Old 02-16-2006, 05:45 AM   #11
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^^ you sure have alot of spare bolts and dooodads.....
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Old 02-16-2006, 09:19 AM   #12
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Quote:
Originally Posted by dudical26
Does anyone have a link to the other thread about the muffler being hacked up and what it sounded like?
Is this the one you're looking for? http://forums.nasioc.com/forums/showthread.php?t=899213

I was working on that thread for a while, too. Lots of talk about the hack there, but no reviews about how it sounded. Last I heard, sfjohnson (I think) was going to work on sound clips of his hack. Somewhere there's a sticky with all sorts of exhaust sound clips, and there were one or two of a gutted OEM unit, but IIRC, the recording(s) were terrible.

Noizemaker - Yikes! That thing looks abused! So you say the two walls are intact, everything in between was removed, and it sounded like crap? Ok. since I have a way to non-permenantly seal the hole when I want, i think I'll start with just gutting everything between the walls, and go from there. If it sounds so horrible, then I'll cut some openings in the walls to make a larger chamber. I'll try that and go from there.
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Old 02-16-2006, 10:15 AM   #13
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Garie, that's not even... a tenth of it. Those are just some random loose ones from the project right next to there; a 2.2l subie drivetrain swap into a lighter non-subaru chassis. There's probably 3 milk jugs full of bolts in that car, plus another 10 jugs or so kicking around various places.

Hikeeba: Yeah, I beat the crap out of it, took pics and threw it in the scrap pile. I picked exactly the wrong places to cut into it, it seems. The two walls are intact, the tubes are missing entirely, and it sounded okay to my ears. It had a couple of quirks, i'll type more when I get to work.
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Old 02-16-2006, 03:19 PM   #14
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So yeah... sound.

Inside:
you got more burble. Just enough volume to hear what the car was doing, but not enough to be intrusive. Almost overwhelmed at speed by wind and tire noise. At high RPMs there was an "air" sound that joined the exhaust note, picture blowing really hard across the top of a largemouth bottle, that rushing sound before it whistles? That's the sound, and it was about equal volume to the exhaust note.

Outside: I only heard it from outside once, and it was moderately louder, but quieter than a friend's Greddy Evo 2 melon-shooter by a long shot. Kinda thin sounding, not quite raspy, but a little sharp.

I was running a stock uppipe, divorced downpipe, 2.5 midpipe/cat delete, stock/gutted catback.... basically one cat, one resonator total.
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Old 02-16-2006, 05:13 PM   #15
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Very interesting.. Thanks for the great detailed description! You painted an excellent picture there!

I will try the same setup you had. I can always open up the walls a bit to make the chamber larger. This will be going on a stock WRX exhaust; all cats, no mods.
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Old 02-16-2006, 05:55 PM   #16
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Yeah, after seeing how mine was done, i bet if you drop the walls in it, you won't get the whistle sound.

If I were going to do one after seeing this, i'd cut the top half of one baffle out (or hollow a large hole in half), and the bottom half of the other to add some curve to the air to still quiet it a bit. Leaving the full walls was probably what murdered the flow, and caused the whistle.

From the look, the air came in, hit wall 1, slid across the openings, then some got through. It then did the same at wall 2, and then repeated this action at the back wall of the muffler before exiting. If the air could be guided a bit, it'd probably help a lot.
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Old 02-16-2006, 06:00 PM   #17
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Oh, and with all cats in place, I didn't get any midrange hesitation. Car performed identically to my perception, but I could hear what it was doing at low RPMs. Idle was a little bit boomy, I forgot to mention that.
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Old 02-17-2006, 10:33 AM   #18
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Thanks again for all the details Noizemaker. It'll all be good info to consider as I proceed with my project. Thanks!
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Old 02-17-2006, 10:36 AM   #19
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dont be tight spend the extra money as youll destroy the pulse resonance of your exhaust and could reduce power or worse still melt your engine!
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Old 02-17-2006, 01:26 PM   #20
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Quote:
Originally Posted by djviper
dont be tight spend the extra money as youll destroy the pulse resonance of your exhaust and could reduce power or worse still melt your engine!
LOL!
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Old 02-17-2006, 01:43 PM   #21
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Quote:
Originally Posted by djviper
dont be tight spend the extra money as youll destroy the pulse resonance of your exhaust and could reduce power or worse still melt your engine!
Oh noes!!11!

Not the pulse resonance!
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Old 02-17-2006, 02:42 PM   #22
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Yeah, it might induce a bipolarity into the flux transduction field generated by the offset pulse of the exhaust valves in relation to the lobe center of the cams! If you're not careful it could mean that your car ends up with a relative anti-reduction of exhaust interpolated bank-sourced auditory feedback!

OH NOES!
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Old 02-17-2006, 04:28 PM   #23
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If it hasn't already been said. Weld in a Y section and basically have a straight piped exhaust with the OEM muffler outside. It will sound great!
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Old 02-18-2006, 08:09 AM   #24
hikeeba
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Quote:
Originally Posted by djviper
dont be tight spend the extra money as youll destroy the pulse resonance of your exhaust and could reduce power or worse still melt your engine!
I'll pass that along to all the guys who are running without an axleback.

REX8 - I've thought of that, but lack welding know-how and equipment. I thought I'd try something very simple and easy to see how it turns out. Y-pipe mod would be cool though.

Quote:
Originally Posted by Noizemaker
...relative anti-reduction of exhaust interpolated bank-sourced auditory feedback!
Your post had me laughing so hard that I woke up my wifey in the other room!
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Old 02-18-2006, 08:13 AM   #25
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hik running with no back box on is quiet different to chopping parts out of a standard exhaust, but as there seams to be so many "experts" on here ill leave it up to them to explain why!
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