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Old 08-08-2013, 12:45 PM   #1
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Default catalytic converter project help

To save ~$100, I'm fabbing up my own catalytic converter to get my car registered and legal again. I currently have an Artech 3" test pipe.

Here's the cat I'm planning on picking up, 3" inlet/outlet, magnaflow, 16" overall length.

http://www.summitracing.com/parts/mpe-94009/overview/

I'm wondering if any of the fabber's (that's fap with a B) have experience using a 16" body. I'm a little worried I'll have to cut it down too much to meet the ~13.5" actual length and I'll end up trying to weld the flanges right to the cat body. I've searched on summit for a 14" body, but I end up with some $45 off brand cat that I'm a little worried about.

Also, if anyone has a source for cheaper magnaflow that also sells some 3" flanges, please post up.

I'm planning on two of these, I feel like I'm getting raped at $21 each.

http://www.summitracing.com/parts/vpe-1473s/overview/

I don't really want SS for either of these, but it seems like that's all I can find.
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Old 08-08-2013, 02:13 PM   #2
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Don't you want something less restrictive? Like a metal core 100-200 cell cat. I picked one up from performance-curve on eBay yrs ago for <$100. Car passed emissions with it no problem.

400 cell ceramic core:


200 cell metal core:


Aamof I think I still have that ceramic core cat on the shelf. Probably only has ~2k miles on it. Now that would be cheap.

Another pic of the two, metal core on left.
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catalytic converter project help-catalyticconverter03.jpg   catalytic converter project help-catalyticconverter04.jpg  
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Old 08-08-2013, 02:30 PM   #3
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you want a 200-300 cell metal core cat.
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Old 08-08-2013, 02:41 PM   #4
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you want Eastern Part #79130; this is the same one Rob just posted.

http://performancepeddler.com/catalo...r-p-17441.html

or if you if you wanna play it really safe, the 9" version:

http://performancepeddler.com/catalo...0-p-17444.html
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Old 08-08-2013, 04:23 PM   #5
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M2cupcar, how much for the cat, 3"? I'll buy it off you, it really only needs to be used for about a week every two years.

Is it that cut up one on the right or the metal core on the left?

And what are the emission differences between a ceramic core and metal core?

Last edited by curly; 08-08-2013 at 04:24 PM. Reason: god damn hackers
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Old 08-08-2013, 04:56 PM   #6
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Brainy- the problem with that eastern cat is that the inlet/outlet pipes do not taper into the cat body, they just drop off. Unless they've changed it. I had to chop my tubes off and the flare my exhaust out to meet up with the cat body (pic below.) TurboTim found another one for the same price that was built right- a smooth transition from the inlet/outlet into the cat body.

Curly- the ceramic core cat is the cheap one with the heat shields. It will produce better emissions results, but both the cats passed my 90 for roller test here in ATL. Don't recall the difference. Problem with me selling you the ceramic one is I lose my a$$ on shipping compared to selling it locally when you can buy a new one (unchopped like mine) shipped for $50. Here's performance-curve's current budget 3" cat.

wtf?

fixed


good example of the difference- ceramic 400 cell, and below the 200 cell metal core

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catalytic converter project help-catalyticconverter06.jpg   catalytic converter project help-catalyticconverter07.jpg   catalytic converter project help-catalyticconverter02.jpg   catalytic converter project help-catalyticconverter01.jpg  
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Old 08-08-2013, 06:38 PM   #7
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Quote:
Originally Posted by curly View Post
M2cupcar, how much for the cat, 3"? I'll buy it off you, it really only needs to be used for about a week every two years.

Is it that cut up one on the right or the metal core on the left?

And what are the emission differences between a ceramic core and metal core?
Do you have a visual inspection? If not, why not just sack up and get it tested? My car passed (and still does pass) emissions in WA state with no cat and shitty old DSM 450s + resistor pack.
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Old 08-08-2013, 07:03 PM   #8
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What is your allowed emissions in the state? I just passed on Tennessee's with 196ppm HC and 0.32%CO with no cat at all. I have an All-Flow cat from Silicone Intakes to pass the visual.
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Old 08-09-2013, 03:41 PM   #9
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WA and OR are probably very similar in emissions requirements, I can't remember the exact numbers off the top of my head. The only use a mirror to check under the car on about half the OBD-1 cars that come in, but I'm guessing with my fender stickers, oil cooler in the nose, roll bar, stripped interior, extractor vent, brake ducts, loudish exhaust, and RFL BOV they're going to check mine. So I haven't bothered trying it without yet.

I'm temped to try the silicone intakes unit, however I'd be spending $40+shipping, and there's a chance it won't pass, I've never tested without a cat. So I'd rather spend the extra $30 for a real cat. Even with the fake one, I'd be swapping it in and out for Abe's superior fabrication skills. I'm not 100% confident I'll pass without one anyways, I'd rather not take that chance.

Emissions testing has always been a black hole for me. My fuel pump relay jumper fell out driving out after a failure once, failed for being too loud, my laptop died with my emissions map loaded and the engine wouldn't restart, plus a handful of other failures just from testing.
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Old 08-14-2013, 11:07 AM   #10
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Thunderbolt cats are pretty good, and the same price as the fake cats.
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Old 08-16-2013, 03:13 PM   #11
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I bought the thunderbolt for $47 and some 3" flanges. Flanges are here, I'm waiting on the cat. Hopefully with my rebuilt head not smoking like crazy, I'll breeze through the visual and output tests with ease. I know they like 10* timing like stock, my car always has issues idling like that.
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Old 08-17-2013, 06:20 PM   #12
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Dammit, I need to move to Oregon >:(
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Old 08-17-2013, 07:38 PM   #13
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Don't worry, this is only for OBD-1 cars. Your NB would still have to return OBD-2 codes, although I don't think they put you through a sniffer.

Outside of the Portland and/or Medford area, no testing is required. Portland goes back to 1975, Medford goes back 20 years, or currently 1993.


To add to my catalytic converter story, the Thunderbolt (sounds like a character out of G.I. Joe) cat is welded up and ready to go, although it took some creative thinking on my part.

Please remember that the excess pipe on either end of the cat has a 3" INNER diameter. If you plan on using a standard 3" flange, it won't fit over. I had to cut off the excess, weld in 3" exhaust tubing spacers, and then slide my flanges over and weld both pieces on. I might take a picture later if I can clean it up a little more, it's currently covered in flux core slag, dust, and sloppy welds.
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Old 08-17-2013, 08:35 PM   #14
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I dont understand why you bought 45 bucks worth of ss flanges?

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Old 08-17-2013, 09:56 PM   #15
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I didn't? They were $28 total after shipping. Those $21 SS ones at summit were linked just because they were the only ones I could find. I finally found some on ebay. They said they were mild steel, but they were coated with some sort of chrome crap that made it difficult to weld.
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Old 08-17-2013, 10:25 PM   #16
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Yep, Basically whatever you buy you need to run it on a belt sander till its nice and fresh metal underneath if you want teh pr0n weldz.

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Old 08-18-2013, 10:14 AM   #17
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Curly if you need it just for emissions i'd go with a very high count.

Also if u're going to pull it every 2 years why not just install vbands from ebay? Should be about the same price as the flanges from summit.

Err i'm late to the show. GG.
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Old 08-18-2013, 02:52 PM   #18
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Because Abe's dp and midpipe both have 2 bolt flanges. I could of gone with all V-bands (I think for no extra cost even) but decided not to, so I could buy an off the shelf 3" cat from enthuza, FM, etc. Jokes on me, I built my own anyways. I wouldn't trust my welding skills on V-bands anyways.
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Old 08-20-2013, 04:29 PM   #19
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Quote:
Originally Posted by ayb88 View Post
Wow, I had no idea people can make their own Cat's. Why don't a lot more people do this?
They do. Welcome to custom exhaust. They are not however making their own cats from scratch, they buy a cat and weld the flanges they need for it to bolt in.
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Old 08-20-2013, 04:31 PM   #20
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Quote:
Originally Posted by Leafy View Post
Thunderbolt cats are pretty good, and the same price as the fake cats.
not from the pics I've seen of them.
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