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Old 10-14-2006, 09:53 PM   #1
scrat
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Default cat converter flow measurements

Here's the latest data from Scratflow enterprises. I had my TurboXS cat converter self-gut a few weeks ago, so I had a chance to drive around catless for a while. The car seemed pretty responsive, but I want to run a cat, so I ordered another one from TurboXS. When I got it in, I checked the flow compared to the stock cat. The results were pretty disappointing; the new cat only reduced the back pressure from the stock value of 2.2psi down to 1.4psi, and the car felt pretty sluggish. I decided to get a Magnaflow metal substrate cat, part number 59959 @$114 on Ebay, reputedly flowing 570cfm, and check that out to see if it was any better. What a difference! The back pressure on that cat was only 0.7psi, less than half that of the TurboXS cat. Guess who's going to Lou's custom exhaust next week to have my blown cat refitted with the Magnaflow?

Here's a nice graph of all my results:



Mark
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Old 10-14-2006, 10:27 PM   #2
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You are the MAN! This is exactly the kind of info that I'm looking for at this moment. I've been wondering if a seperate cat or catted DP is better and if so, which catted DP is best.

Buck
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Old 10-15-2006, 12:39 AM   #3
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Nice info, you kick ass! I'll add this to my exhaust FAQs when I get a chance.
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Old 10-15-2006, 03:15 AM   #4
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questions: who is scratflow enterprises? from your username is it your company? I can't find any info on google.... I'd like to see the more on results.

in the graph above, is Metal Cat the brand Metal Cat (as in the AU company) or a metal substrate cat?
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Old 10-15-2006, 07:24 AM   #5
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en3d, refer to this thread.
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Old 10-15-2006, 08:48 AM   #6
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Quote:
Originally Posted by en3d View Post
questions: who is scratflow enterprises? in the graph above, is Metal Cat the brand Metal Cat (as in the AU company) or a metal substrate cat?
Sorry, Scratflow was just a late night attempt at humor. I'm just doing these flow measurements with a leaf blower and some primitive, homemade instruments, but it seems to work quite well.

The cat I tested was a Magnaflow universal replacement cat converter, part number 59959, 3" input and output. This unit has a metal substrate core, and is reputed to flow 570cfm. Here's a link:



http://www.car-sound.com/02product/d...niversal=59959

Thanks for all the good feedback; I still can't understand why the manufacturers of exhaust components can't supply this information. It's pretty easy to accomplish, and it would help people make informed decisions on which components are best for their cars, or what the compromises between flow, quietness, etc might be.

Mark
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Old 10-15-2006, 10:40 AM   #7
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Quote:
Originally Posted by scrat View Post
and it would help people make informed decisions on which components are best for their cars,
there's your answer right there!



thanks for your work on this stuff. my eventual goals are to put an aftermarket metal substrate in place of the oem 3rd cat, and this just sealed the deal.
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Old 10-15-2006, 11:37 AM   #8
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I just bought the same high flow cat off of ebay. Now all I need is an aftermarket DP and my exhaust will be set.

I'm running ported and coated OEM manifolds, (Crucial DP soon), Magnaflow Cat and OEM STI exhaust from there (which had some nasty welds that needed to be cleaned up). A little exhaust welding and maybe a custom mid pipe and I'll be done.

Scratmatic exhaust to the rescue
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Old 10-15-2006, 12:13 PM   #9
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thanks guys that clears things up.

I run the brand Metal Cat converter.... http://www.metalcat.com.au/ and they here is a flow test result (not much info) http://www.metalcat.com.au/images/Me...Comparison.jpg (this is link on the main page). There is a local guy who owns an exhaust company and we talked about it and he thinks highly of Metal Cat.
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Old 10-16-2006, 06:48 PM   #10
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Quote:
Originally Posted by en3d View Post
I run the brand Metal Cat converter.... http://www.metalcat.com.au/ and they here is a flow test result (not much info) http://www.metalcat.com.au/images/Me...Comparison.jpg (this is link on the main page). There is a local guy who owns an exhaust company and we talked about it and he thinks highly of Metal Cat.
I checked out their website, and it looks like those cats might be even better than the Magnaflow versions. Is there a local (US) vendor for them, and how much do they cost?

Thanks

Mark
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Old 10-16-2006, 06:57 PM   #11
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Quote:
Originally Posted by scrat View Post
I checked out their website, and it looks like those cats might be even better than the Magnaflow versions. Is there a local (US) vendor for them, and how much do they cost?

Thanks

Mark
Believe it or not, JC Whitney sells them. Go figure.
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Old 10-16-2006, 07:08 PM   #12
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More great data, scrat!

BTW, for those who haven't seen his other posts, scrat said he's more than happy to test exhaust parts if they get them to him, so any locals should hit him up!
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Old 10-16-2006, 08:21 PM   #13
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where is his local?

side note: i want to put on a high flow cat, but where is the best place to put it? higher on the DP closer to the turbo or farther back where the 3rd OEM cat was?
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Old 10-16-2006, 09:31 PM   #14
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cats will provide less restriction to flow as the gasses cool off.

however they will not provide the same degree of catalytic action.

like everything, it's a tradeoff.
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Old 10-16-2006, 09:58 PM   #15
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^^ What he said. Closer to the engine = quicker lightoff but more backpressure due to the greater volumetric flow rate of the "hot" Exhaust. Underfloor = less effective as an emissions catalyst (especially during cold start and possibly idle) and also a greater risk of fire if you enjoy driving in tall grass (or can't keep all 4 wheels on the tarmac at your local track), but less backpressure.

On a side note, has anyone pooled together technical data on the stock cats? i.e. I'm thinking cells per inch, primarily, but length, etc. would be interesting. More CPI = more backpressure. I'm assuming that the stock underfloor cat is less dense, which would help explain why it's "less bad" for backpressure...
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Old 10-17-2006, 03:13 AM   #16
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Quote:
Originally Posted by imma_stocker View Post
where is his local?
Quoted from the STi vs. ProDrive Oval Axleback thread:
Quote:
Originally Posted by scrat View Post
metrowest Boston
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Old 10-17-2006, 09:32 PM   #17
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Quote:
Originally Posted by The Deliverator View Post
Believe it or not, JC Whitney sells them. Go figure.
Grrr. Wish I had known this before I bought the Magnaflow. I think the Magnaflow is quoted as 300cells/inch. The pic at JC Whitney almost looks like it has a heat shield installed. Does anyone know if this is true? If it does, I will definitely pick one up.

Thanks

Mark
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Old 10-19-2006, 09:21 PM   #18
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Default Magnaflow looks good

Got the Magnaflow from UPS today. It looks nice. 3" in and out. The diameter of the cat portion appears to be about 4" and is tubular...should flow nicely.

Also, it's nice and light. Just guesstimating, I'd say less than 2lbs.

Buck
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Old 10-21-2006, 01:37 PM   #19
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Default And the winner is....

Metal Cat. I just got mine from JC Whitney, and here are the results. The Metal Cat beat the Magnaflow by almost a factor of two! We're getting really close to just an open pipe, now!



Just to avoid confusion, the cat in the older graph marked "metal cat" is now labelled "Magnaflow cat", to avoid confusion with the new "Metal Cat" brand name.

Mark
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Old 10-21-2006, 02:29 PM   #20
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scrat, thank you very much for doing this. I've posted before... I've run four different setup on my car and my current setup:

bosal dp, bosal 3ce w/ a Metal Cat 2.5" welded in, stromung 2.5" midpipe and STi muffler is the one I like the most. low end gains and didn't feel a difference in the top end compared to the 3" exhaust.

I've run (all w/ a high flow ceramic cat):
turboxs
M2
stromung
and my current

sorry for the lack of responses before... work has been killing me.
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Old 10-21-2006, 07:25 PM   #21
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Thanks again for your work, Mark. Could you put the details of the parts you test in the same posts as the images? Basically note that the WRX is the dual-tip model, the Prodrive is the oval tip, the TurboXS cat is the 3" model, etc, etc... It would help reduce any confusion.
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Old 10-21-2006, 08:43 PM   #22
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jcwhitney part number for the cat? or a link to it
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Old 02-24-2007, 05:38 PM   #23
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riddle me this batman

Which outflows which

A. shorty non catted downpipe w/ the 3rd oe cat in place or B. catted downpipe (w/ cat near turbo) and 3rd oe cat deleted.

Looking at the above data it appears the oe 3rd cat is not overly restrictive and given it's location I'd have to say A.???

Obviously the best catted situation is a non- catted downpipe w/ a race cat in place of the oe 3rd cat, but what about the choice between A and B?

No doubt the catted downipe would do better from an emission standpoint (I think anyways).

TIA
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Old 02-24-2007, 06:20 PM   #24
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Quote:
Originally Posted by BIGSKYWRX View Post
riddle me this batman

Which outflows which

A. shorty non catted downpipe w/ the 3rd oe cat in place or B. catted downpipe (w/ cat near turbo) and 3rd oe cat deleted.

Looking at the above data it appears the oe 3rd cat is not overly restrictive and given it's location I'd have to say A.???

Obviously the best catted situation is a non- catted downpipe w/ a race cat in place of the oe 3rd cat, but what about the choice between A and B?

No doubt the catted downipe would do better from an emission standpoint (I think anyways).

TIA
I don't think we have enough information to answer, as it depends on how high-flow the cat in the downpipe is. If it flows as well as the Metal Cat, it might be the better choice, despite its location so close to the turbo.

For reference, Rich from www.daddysscp.com dyno'd the stock 3rd cat at a 10 hp loss compared to their 3CE on an otherwise basic Stage 2 car.

Last edited by TurbojonLS; 02-24-2007 at 09:14 PM.
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Old 02-24-2007, 08:55 PM   #25
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Quote:
Originally Posted by BIGSKYWRX View Post
riddle me this batman

Which outflows which

A. shorty non catted downpipe w/ the 3rd oe cat in place or B. catted downpipe (w/ cat near turbo) and 3rd oe cat deleted.

Looking at the above data it appears the oe 3rd cat is not overly restrictive and given it's location I'd have to say A.???

Obviously the best catted situation is a non- catted downpipe w/ a race cat in place of the oe 3rd cat, but what about the choice between A and B?

No doubt the catted downipe would do better from an emission standpoint (I think anyways).

TIA
This is all based on my butt dyno...

#1 My stromung setup was the 2.5 shorty DP w/ a flat plate and a what later I determined was magnaflow high flow ceramic cat (based on part number on the cat) the DP was a stromung part the cat was not welded in after and a stromung 2.5 3ce.

#2 then I ran the my current bosal with the stock 3rd cat while I had the bosal 3ce welded with the Metal Cat cat.

#3 then I installed the bosal w/ Metal Cat.

There was no noticable difference between #1 and 2 based on my butt dyno. some will argue flat plate for the stromung... blah blah blah. but show dyno graphs on that topic.

with the #3 setup (my current), a very noticeable difference.

I didn't reset the ecu when swapping out these 3 setups and they were on the car in the sequence listed above so I knew how the car felt before swapping these parts.
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