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  #1  
Old 08-05-2007, 05:39 PM
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Nevin Nevin is offline
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making a header-back exhaust, couple of questions

Ok, like the title says, I am pondering the idea of a making a custom header back exhaust for my car. I'm no stranger to fabrication as I've made custom IC pipes already for two cars owned previously as well as other exhausts so yes, I will be doing this myself. I'm thinking I'll probably just buy some mandrel bends off ebay (had good luck before) and do the rest in mild steel.

Anyways, what I'm thinking is getting rid of the cats righ after the headers as well as the stock one and putting in a new ceramic cored cat probably of a 2.5" diameter. Would that be enough for the car? What is a good diameter exhaust for these cars? I would think that 3" would probably be slight overkill as well as adding un-needed noise to the car. I'm basically trying to help it breath a little better (maybe improve mileage a little) and give it just a bit more growl. I'm thinking I would probably go with a Flowmaster 80 series, and probably still put in maybe a 24" resonator. Or, should I put in two smaller cats, and have it Y together after those and then go into the piping?? You tell me! Also, I considered going catless.. but I'm past that point in my life where I'll do anything for power. I've never heard of anyone getting a ticket for that here in Iowa, but I don't want to be the first. ALso, I mean come on, it's the 21st century, we should be able to make power without hurting our air quality.


So, if you've done something like this, please let me know what works, what doesn't, should I even bother... etc.

Thank you.
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Last edited by Nevin; 08-05-2007 at 05:45 PM.
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  #2  
Old 08-05-2007, 06:30 PM
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2" for na is going to be about as larger as you're going to want to go up to the primary cat. You can go to 2.5 after the primary cat. Definitely either replace the secondary cats up by the exhaust manifolds with new cats or with "solid" resonators (you don't want ones with any packing that might shed and foul up the primary cat. This will prevent the cursed 3k resonance that shows up if you just eliminate the secondary cats. There are plenty of folks on the network who have installed various exhaust systems. Check out SVXFiles locker for the dozen or so he's done
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Old 08-05-2007, 10:02 PM
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So, I SHOULD put secondary cats in? Can I just do two 2" secondaries and that's all, then have it just Y into 2.5" ?? Yeah, I don't want any sort of rasp or anything like that. Wouldn't it be better to go like 1.75" from the manifolds though?? Seems like 2" is a bit large to me... What is the I.D. of the stock exhaust anyways, do you know??

Sorry for the nob questions, but just still exploring the site and trying to find what all is on here!
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Old 08-05-2007, 10:24 PM
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Take a look at this system. You'll have to hit up svxfiles and svxcess for the specifics, but I believe it's 2" from the headers, through Aero resonators, into a 2" dual in, 2.5" single out magnaflow cat (I have one of those on my car), with 2.5" plumbing through another Aero res, and into the muffler.

http://www.subaru-svx.net/photos/user.php?svxcess
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Old 08-05-2007, 10:52 PM
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Sweet, that does look good. Any idea on what kind of a muffler it goes into?

That seems like a good setup though, I think I'll try mine like that!
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Old 08-05-2007, 11:46 PM
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svxfiles (Old Tom, as he is also known), is the guy to talk to. He came up with that system, and from what I've heard thinks it is THE exhaust system for a stock powered SVX. Fire him a PM and I'm sure he'd be happy to help you out with the specifics.
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92 Ebony Mica LS-L "A Rolling Restoration": 223,250 KM - Sleeping
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Old 08-05-2007, 11:49 PM
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Actually, here's the thread detailing that system:

http://www.subaru-svx.net/forum/show...t=37523&page=2

Apparently it simply runs through the stock muffler, although I'm sure any single in/dual out aftermarket piece could be made to work.
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92 Ebony Mica LS-L "A Rolling Restoration": 223,250 KM - Sleeping
2007 STi 6MT, Stance GR+ coilovers, PWR Rad, JDM hood badge, svxfiles 6000K HIDs, JDM Clear Corners, $15/15 min mod, $20/20 min mod, Energy Swaybar Bushings, Hella Supertones horns, Gold STi BBS rims, Group A lightweight crank pulley, A/C system removed, Custom header-back exhaust, Hybrid carbon/metal rear sway bar, restored headlights with CCFL halos
2008 Subaru Legacy Spec B - Diamond Grey Metallic - Sold
2020 Ram 1500 Longhorn - Red Pearl

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