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Old 07-02-2005, 07:26 AM   #1
Al_Smokemcrack
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Default Custom Stainless Exhaust

I know a guy who's a tech in a customs shop. Since they regularly service people's hot-rod needs, they recently acquired one of those really spiffy hydraulic mandrel tubing benders. This guy was okayed by the owner to bend custom exhausts for people after hours. He told me he'd fabricate me basically anything for $100. I was thinking that I might bring him some stainless tubing and get something better than stock bent, but I'm not really sure what to go with. I would like to keep the original cat and muffler on there since I'm a cheap muthahucka, but I'm not above buying a cheap-ish header like a Borla.

So far, I have these ideas:
  • New pipes made exactly like stock pipes. Theorectically, exactly the same, but stainless.
  • New pipes bent with longer, smoother bends, of course to fit within the tunnel; stock diameter (2.25"? Gotta measure it). Should net some small gains and change the note a bit.
  • Something of wider diameter but with narrowed ends for the flanges such that it'd fit the existing cat and muffler. Might quiet things down a bit and change the note since it has a larger inside volume, but since the cross-sectional area is the same, I shouldn't, theorectically, get any more flow than the stock diameter. I'm thinking this is just a giant waste of time.
  • Something of wider diameter that I could just stack up in the garage until I get over my tightwad complex and pick up a larger diameter cat and muffler. Obviously, the same gains any other bigger exhaust would get. I just wonder how big I should go. 2.35"? 2.5"?

I might have him bend me a cat-delete pipe and I'll weld myself some O2 bungs onto it, just because. It might be fun to slap on for normal use and to put the cat back on when I have to pass emissions.
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Old 07-02-2005, 01:39 PM   #2
RS_to_WRX_swap
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If you have 2.5L motor i would go with 2.5 inch pipe. Thats what i put on a friends 2.5RS and she lost no torque despite what others "think" around here. If i were you i would just do the cat-back right now just to keep the cost down. As for the muffler, get a turbo muffler. They are only $28, they flow much better, and sound great.
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Old 07-02-2005, 04:01 PM   #3
LA
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i say if you know this guy does good work, do it right the first time. don't be that cheap and keep your stock muffler and cat. if you don't have emissions to worry about i would go catless and you can always find a decent muffler used in the forums usually or wait to get one you want and do atleast 2.25-2.5 inch pipe. that's my .02
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Old 07-03-2005, 01:50 AM   #4
Al_Smokemcrack
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I'll probably have him bend me a whole pipe using 2.5" tubing and hardware, plus a cat delete pipe just because. I figured I'd just stick it in the garage until I get around to getting the bigger muffler. Plus, since you say turbo mufflers are so cheap, I might have to do that. The only question I have is, since turbochargers use up alot of the energy present in the exhaust gas stream, turbo mufflers need not attenuate so much; wouldn't one of those on an N/A engine be louder than sin?
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Old 07-03-2005, 08:44 AM   #5
Kevin Thomas
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Where is this shop located? Can you provide a number as well? I may need some piping bent for 'non-N/A' purposes. Thanks!


On your end, get yourself a cheap 2.25" muffler (Dynomax for example) and a cheap 2.25" high flow cat converter (can be found at Autozone for example). Mate these up with 2.25" piping from the cat back and call it a day. If you still have pennies laying over, may as well get the header done too.
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Old 07-03-2005, 11:10 AM   #6
shoeler25
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I would go with option 2. Smoother curves with 2.25 piping, and if you must go bigger, unless a turbo is in your near future plans no larger than 2.5. Kevin has a good idea too, but dont use dynomax, I havent seen one that hasnt rusted to all hell in a few weeks. If your goin stainless piping, you might as well get a muffler made out of some quality stuff as well, Id recommend a borla universal or magnaflow. Both are still cheap.
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Old 07-04-2005, 01:04 AM   #7
HolyCrikey
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Again, we have the debate of 2.25 vs. 2.5 on the N/A's. If this guy is good at his job and his bending of tubes, I'd wait with what money you have. If you wanna pass inspection, go with a high flow cat of some type (randomtech?) and mate it up with whatever piping you want. I seriously doubt you'll see much degredation of performance by stepping up from 2.25 to 2.5. Lately, I even took advice from a buddy who has been working with Subaru for years and years. He's done many buildups, knows practically everything there is to know about aftermarket modification, and he assured me that when I mate my 3 inch axleback to a 2.25 inch midpipe, I'd notice little, if any, performance decrease. So, as always, the jury is still out on how big we can make our exhaust without performance problems. The N/A forum will probably always advise to simply go with 2.25, and I also stand by that.

I also gotta gree with Kevin Thomas and shoeler25. There are plenty of cheap, yet nice, universal mufflers that you can get welded into whatever exhaust you have. Many people go with Magnaflow. Pick a muffler, add it on. You can get whatever diameter outlet you need. There are some real nice axle-back systems out there as well. Many recommend Stromung or Borla or Cobb. All depends on how much you can put out there.

I can tell ya from experience though, don't go with something you just lazily decide to put on. If you want a nice high flow cat system, wait and do it. If you want a high quality, possibly name brand muffler, save for it. You'll be much happier in the long run.
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Old 07-04-2005, 09:58 AM   #8
Tim Sanderson
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Jegs sells a high flow cat that looks exactly like the random tech one. The description of it sounds the same too. 149.00$. Bare cat. Perfect time to integrate it.
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Old 07-04-2005, 07:33 PM   #9
Patrick Olsen
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I'd be surprised if the stock system isn't already stainless. Pretty much every automaker has been using stainless for years, now. So there would be little, if any, gain by copying the stock exhaust but with mandrel bends. I would advise you to go with larger piping throughout, and do as the others say - get a universal muffler for probably under $50. If you can swing the hi-flow cat, do that, too - I have one of the Dynatech Powertech converters that Jegs sells (I got mine somewhere else, same price though). An MRT-style header should be pretty easy to fab up, and would net you the biggest gains.

Pat Olsen
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Old 07-05-2005, 12:58 PM   #10
wgb113
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The stock piping on my '04 RS was stainless as confirmed by the mechanic that fab'd my custom cat-back.

It's only 1-7/8" though and I went with 2-1/4" throughout for the custom job. I used a Magnaflow resonator and Borla ProXS universal muffler & tip.

Bill
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Old 07-06-2005, 10:11 AM   #11
Al_Smokemcrack
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Quote:
Originally Posted by Kevin Thomas
Where is this shop located? Can you provide a number as well? I may need some piping bent for 'non-N/A' purposes. Thanks!


On your end, get yourself a cheap 2.25" muffler (Dynomax for example) and a cheap 2.25" high flow cat converter (can be found at Autozone for example). Mate these up with 2.25" piping from the cat back and call it a day. If you still have pennies laying over, may as well get the header done too.
The shop's here in Rochester, NY. Since it's all after hours work, I'm not sure whether he'd like for me to post the stuff on the internet -- he's gotta sleep, 'mano. I'll run it by him next I see him and if he's okay with it, I'll PM you a number and a name.



Quote:
Originally Posted by wgb113
The stock piping on my '04 RS was stainless as confirmed by the mechanic that fab'd my custom cat-back.

It's only 1-7/8" though and I went with 2-1/4" throughout for the custom job. I used a Magnaflow resonator and Borla ProXS universal muffler & tip.

Bill
I know that the stock exhaust is stainless - it's worth the extra cost to OEM's to make them stainless to begin with as it cuts down on warranty claims quite a bit. It's crappy stainless, though. I was going to use a higher grade stainless. Probably something 300-series. More corrosion resistant and stuff.

What'd you do about the header? Just size the pipe down up there and put a flange to fit the header, then run larger the whole rest of the way back?
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Old 07-06-2005, 12:38 PM   #12
wgb113
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I only did from the last cat back. He unbolted it at the flange, cut the flange off, welded the Magnaflow resonator to the flange, bent some piping, welded the tip to the muffler and then the muffler to the piping.

I'm thinking about adding another resonator to tone down the deep bass sound I get in the cabin. Apparently the Borla Hush made for the WRX uses two resonators to quiet it down.

He used a larger guage stainless than stock for the piping.

Bill
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Old 07-06-2005, 07:46 PM   #13
Patrick Olsen
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FWIW, our 2.5L 165hp (stock) engines fall in between 2.25" and 2.5" on Dynomax's webpage - http://www.dynomax.com/techsupport.stm . For those of us making in the 200hp ballpark, 2.5" is the way to go - even for us N/A types.

Pat
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