High Flow Catalytic Converter / Exhaust Manifold - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 03-08-2005, 10:30 AM   #1
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High Flow Catalytic Converter / Exhaust Manifold

Ok. I have my aftermarket exhaust muffler on, but I think it could sound a lot better with a high-flow exhaust system. I have the stock non-turbo exhaust system which is 2.25" I believe. I want to begin by changing the cat which is the original I believe...Now would it harm my car to get a high-flow catalytic converter since it is an N/A car? What type should I get? I've seen a lot on ebay I might be interested in getting...This is most likely going to be one of this summer's projects, but need ideas first...
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Old 03-08-2005, 12:09 PM   #2
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No harm....there are so many cheap options out there, I got my 3" all stainless one from summit for cheap
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Old 03-08-2005, 12:11 PM   #3
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check the for sale section...i have a 3 inch in/out catco cat and 3 inch straight through dynomax muffler for sale....



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Old 03-08-2005, 02:03 PM   #4
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Would something like this work?

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
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Old 03-08-2005, 04:06 PM   #5
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isn't that just completely removing the cat? is that what your looking for? i heard that a test pipe has negative effects, in the performance area, on n/a engines
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Old 03-08-2005, 04:38 PM   #6
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Well see I am registered under a country that doesn't require emissions for now...But that might be changing. I figured I would try a straight pipe instead of a cat, but I also heard it has negative effects on an N/A. So I should go with a high flow cat...
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Old 03-08-2005, 05:36 PM   #7
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Originally Posted by rcmdesign
Well see I am registered under a country that doesn't require emissions for now...But that might be changing. I figured I would try a straight pipe instead of a cat, but I also heard it has negative effects on an N/A. So I should go with a high flow cat...
It's not removing the catalyst that causes a problem on N/A cars, it's making the backpressure TOO low ... BUT ... that's only bad if you have a pulse-tuned exhaust setup and it was tuned for use with a catalyst. The reason is because it throws off the tuning by a small margin. The Honduh S2000 has this problem, but with mufflers: if you put a high-flow muffler on one there are plenty of dyno-sheets showing a loss in horsepower.

There's a LOT of really good info on naturally aspirated cars out there when it comes to exhaust tuning. (More than there is on turbo-cars.) The real reason for not removing the catalyst is that, if it gains 5 bhp on a turbo-car, it's likely to only gain 1-2 on a N/A car ... if you're lucky. And 2 bhp is NOT worth the huge increase in toxic emmissions ... not to mention how much louder the car gets.

Adrian~
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Old 03-08-2005, 05:41 PM   #8
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Thanks for the info. But putting aside all other cars for a moment, if I get a high-flow cat on my car will it do anything for performance? You mentioned 1-2 HP...Will a high-flow cat make it a LOT louder than stock? I just want my system a little bit louder. Maybe 30% louder...
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Old 03-08-2005, 05:58 PM   #9
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if you want 30% louder wont doing 2.5" piping throughout do the trick AND give a noticeable addition in hp
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Old 03-08-2005, 06:37 PM   #10
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highflow cats flow the same as any other cats guys... look at all the test doen on other boards online
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Old 03-08-2005, 07:10 PM   #11
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I was told that I could install the 2.5" stock turbo exhaust system on my car to get better flow. Just not the downpipe of course...
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Old 03-09-2005, 12:17 AM   #12
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Originally Posted by rcmdesign
I was told that I could install the 2.5" stock turbo exhaust system on my car to get better flow. Just not the downpipe of course...
The stock exhaust is a 2.25" I.D. ... maybe it's 2.5" on the exterior? Just find a Viggen owner who has upgraded. The stock Viggen exhaust is stainless steel, mandrel-bent, and comes with straight-through mufflers just like a performance exhaust. The standard turbo-mufflers are not straight through like the Viggen's are. They're all pretty quiet on the turbo engines ... could be nice-sounding on N/A ... but who knows?

I tried my C900 n/a without catalyst for a very short time ... it was most unpleasent. It makes the car sound very raspy, and I noticed no increase in power ... in fact it felt downright sluggish below 3,000 rpm after I did that.

If you don't have headers, those will make a HUGE difference in power. if they're made right. On a N/A car headers are the way to go.

Adrian~
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Old 03-09-2005, 06:56 AM   #13
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Sweet. So where might I go about getting a nice set of headers for an N/A.

Mike Connolly a.k.a Meatball had a nice header on his N/A. See pic below.



I am assuming by headers you mean an exhaust manifold?

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Old 03-09-2005, 07:15 AM   #14
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on an n/a car... they are headers depending on design or could b manifold.... just like on a turbo car u have a mnifold stock but u can have tube headers made with a flange for the turbo
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Old 03-09-2005, 08:06 AM   #15
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Originally Posted by rcmdesign
Sweet. So where might I go about getting a nice set of headers for an N/A.

Mike Connolly a.k.a Meatball had a nice header on his N/A. See pic below.

I am assuming by headers you mean an exhaust manifold?
As a general rule, manifolds are cast and headers bent ... but the terms get mixed up constantly. There's no point in trying to differentiate because they get interchanged so often.

I'm hitting the books again and doing some research into header-design because I know the owner of a Subaru-tuning company who is looking into making some exhaust headers for the WRX/STi. All the existing ones on the market have some serious flaws. I'm also looking into pulse-tuning, but that's another story and may actually become proprietary because pulse-tuning is a reiterative and complicated process. Most of the formulas you read in books about it are very rough estimates which will change from engine to engine ... they're only guides and blunt tools, not a fine instrument, which is what I'm looking to make. (It's been done I'm sure, but I've not found any really published documents on the matter. Philip Smith's stuff, and Bell's stuff is too basic and general)

Anyway .. now that you're probably not paying attention anymore ... here's some good info to consider about headers (everything below here in bold will have an appropriate reference picture at the bottom of the post):

4-2-1 headers, commonly called "tri-y" headers tend to help mid-range torque quite a bit, but, when compared to a 4-1 design they lack upper-end power. The precise reason for this is complicated and has to do with the stopped-length dampening and delaying the scavenging wave. 4-1 headers, when made correctly, generally make considerably more power because the scavenging wave is much stronger. The downside is that you have very low torque below 3500 or so. (Rough estimate, I've not done any pulse-tuning calculations with the B234i.)

Y-pipes with small expansion megaphone are a good way to make up for the lack of scavenging strength on Tri-Y headers. Basically the final "Y" in the header constricts smoothly to an orifice and then expands. This causes the reverse scavenging wave to be much stronger. This is not a subject delt with in "The Scientific Design of Exhaust and Intake Systems" ... but that book is rather old, albeit good.

My money goes on either a REALLY well-built stainless Tri-Y with expansion cone if you want torque ... or with a REALLY well built 4-1 design with a merge collector with megaphone if you want SERIOUS horsepower and top-end.

(Burns' Stainless refer to small expansion cones as transitions. Sorry for the confusion.)

Awesome 4-2-1 header with expansion cone:


Awesome 4-1 header with small expansion cone and ultralight muffler on a McLaren M10B Formula 5000:


Y-pipes with small expansion megaphone:


4-1 Merge-Collector with long expansion cone:


Coolness in a can, man. Careful about headers with excessively sharp-bends.

Adrian~

p.s. Pics courtesy of Burns' Stainless. Check em out: http://www.burnsstainless.com/index.htm
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Old 03-09-2005, 10:53 AM   #16
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Interesting. So would I have to have to get a header custom bent for my car? Or is there a place that sells them for a 2.3L N/A...And would it cause a check engine light to come on. It's a 1995 so I only have one O2 sensor...
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Old 03-10-2005, 05:13 AM   #17
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Interesting. So would I have to have to get a header custom bent for my car? Or is there a place that sells them for a 2.3L N/A...And would it cause a check engine light to come on. It's a 1995 so I only have one O2 sensor...
I don't know of anyone who makes headers for the 2.3L. Sorry. O2 sensor shouldn't be a problem, but custom headers aren't cheap.

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Old 03-10-2005, 09:59 AM   #18
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Rob:

Have you tried to get a hold of Meatball - I have a 900's as well and would be interested in a header - been doing alot of searching and have found nothing - so far.
He has done some other interesting little bits to his, I would like to know where he sourced his stuff. But I cant find the link to his email address had it but it gone now.
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Old 03-10-2005, 10:34 AM   #19
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I've emailed him before. I met him at the Saab Convention in 2003. Nice guy. Tried to sell me all sorts of stuff there...He said he was starting a company to sell parts for the NG900. He custom makes all his parts. He was a member here for a while, but all the turbo guys pissed him off about his HP numbers. They didn't believe they were achievable in an N/A...Haven't heard from him since...

His car can be seen at http://saabpics.org:3000/gallery/900S


EDIT: OH SHIT!! HE WRECKED HIS CAR!!! SEE PHOTOS AT THE GALLERY ABOVE!




Maybe he is parting it out! I would LOVE to get a hold of some of his engine stuff...
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Old 03-10-2005, 10:44 AM   #20
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Ouch! What kind of numbers was he claiming anyway?
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