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Thread: High flow catalytic converter. Worth it or not?

  1. #1
    Join Date
    Sep 2003
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    Spain
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    Default High flow catalytic converter. Worth it or not?

    Hello DSMers I was wondering if changing the stock catalytic converter of my 2gen GST to a high flow one will make any notticeable gains in HP.

    How much HP gain should i spect?

    Or will not improve it very much?
    Is it worth? it costs me around 300$

    I know it's better to pit a straight pipe instead of a cat but i want to pass emmissions tests. In Spain is illegal to drive without a Cat.

    Thanks
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  2. #2
    Join Date
    Feb 2004
    Location
    Ann Arbor, Michigan
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    Default

    I would buy the Test Pipe because you would get alot more gain out of that than a High Flow Cat, and also is alot cheaper, than when you go to your vehicle tests, just swap out the test pipe for your regular cat.
    2005 Evolution VIII MR

  3. #3
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    Spain
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    Default yes

    Yeah, i thought about doing this, but i thing i will have trouble with the rear o2 sensor if no Cat is present and get a CEL. So i prefer to have a Cat and aboid more problems.

    I don't know but if there's a big difference between having a high flow cat or test pipe, then maybe i should try a test pipe, but if we're talking about only 4-5HP more using test pipe then is not worth the efford.

    Does anybody have a high flow cat on his car?
    If so, are you happy with it? Should put one or try the test pipe?

    Thanks.
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  4. #4
    Join Date
    Mar 2004
    Location
    central, NY
    Posts
    2,504

    Default HIGH FLOW CAT

    I have read that Random technology convertors have shown to be equal to th test pipes. I do not know how much HP a high flow would give you though. For a stret car a cat is legal and morally correct. On a race car in the states it is OK to remove the cat. If you have addressed other options for HP then I guess the cat might be worth it. $300. could be used for something else for more power than the cat. IMHO. Mark

  5. #5
    Join Date
    May 2003
    Location
    Cleveland
    Posts
    716

    Default

    A "high flow" converter is no different than a stock on, it just has bigger inlet and outlet. Buy a test pipe, or make one for 10$ you will be much better off. See how many of the fast DSM's run "high flow cats" The number will be in the area of zero :wink:

    If you dont believe that they are in no way internally different, then waste your money, buy one, and compare it to your sock cat and fell like an ass for it.
    93 Dodge Colt. 708whp
    10.5@149mph. Retired @200mph

    87 Rx-7. 1st ever 4G powered @567whp

    89 Supra Turbo-Targa-White-Sex

    97 Tercel BlackHawk- "Mr Stinkypants"

    92 BMW 318i-Saturday Night Hoetaxi


    Don King for a Highway near you....

  6. #6
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    Default

    Stock cats generally get really clogged with crap, so I say any change would be a good change. You could also just find a cheap cat and use the straight pipe untill you must check the car's emmissions, then switch back.

    You have the muffler cut off right, with just a straight pipe? If you made a straight pipe for the cat too, it would support enough exhaust flow to run some more modifications without buying a standard exhaust.

    $300 for a Cat? Don't buy it...there are good ones for under $150
    '90 AWD TSI: 3"TBE, FMIC, 7cm ported 2G exh. mani, TO4B 50trim, 550's, 255lph, -6AN from filter-rail and rail-AFPR by Aeromotive, AFC, 2G MAS and 3" intake, Pocketlogger. Sold
    '92 AWD TSI: 6Bolt/4bolt (March), 2G MAS, Home made 3"=2.25" intake pipe. Ported O2 and amazingly uncracked 1G mani to 7cm, no cat, straight 2.5" in place of muffler. XTD 2200lb PP and 6pck sprung disk, Walboro 190, 550's, pocketlogger, ebay MBC, SAFC, MHI EIII16G.

  7. #7
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    Default i'm sorry but...

    I'm sorry coltboostin but you'r not right about they're the same. look at this picture:


    Our stock one doesn't have the "holes" that big. They have a kind of ceramic honeycomb or something like that with a very little holes.

    About a test pipe es better than any kind of cat i agree, but not all cats are the same.

    I write again my question, what will happen with the rear o2 sensor if there's a straight pipe instead of a cat? a CEL?

    Yes keltonDSMer, i took out the muffler that the previous owner put there and i welded a stright pipe with a splitted rear end.

    About the cat being so expensive i know it but it's because it has documentation that acredites that is under the laws of spain. We call this "homologado".

    If someone tells me how have no trouble with the rear o2 sensor i will go ahead and put a straight pipe instead of spending that money.

    Thanks to all.
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  8. #8
    Join Date
    Jun 2003
    Location
    Lexington, KY
    Posts
    490

    Default

    Since you have a 2g, then you should be able to get DSMlink to take car of things. I have a 1g so Im not sure how everything works, but I know you can access and control a lot of things with it. I would do some research into one. good luck

  9. #9
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    Apr 2004
    Location
    Pueblo, CO
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    Default

    Summit Racing has high flow cats for $70 or so.
    92 Galant VR-4 #526 / 1000

  10. #10
    Join Date
    May 2003
    Location
    Cleveland
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    716

    Default

    That looks no different in "hole" diameter (honeycomb) than a stocker, it looks like it is simply in a different configuration.
    And it still looks like it will flow like a turd.
    93 Dodge Colt. 708whp
    10.5@149mph. Retired @200mph

    87 Rx-7. 1st ever 4G powered @567whp

    89 Supra Turbo-Targa-White-Sex

    97 Tercel BlackHawk- "Mr Stinkypants"

    92 BMW 318i-Saturday Night Hoetaxi


    Don King for a Highway near you....

  11. #11
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    Sep 2003
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    Spain
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    Default not mine.

    I don't want to argue with you but i can guarantee you that my stock cat has the holes smaller.

    Maybe my cat is clogged by carb deposits, i don't know but i can tell you that you can barely see light through it, and this high flow one lets you almost see the other side clearly.

    I will look for cheaper cats here in Spain.
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  12. #12
    Join Date
    Jul 2003
    Location
    Boulder, CO
    Posts
    1,000

    Default

    You could just gut out the stock cat for free, then go find a cheap one if emmissions testing is required again.
    '90 AWD TSI: 3"TBE, FMIC, 7cm ported 2G exh. mani, TO4B 50trim, 550's, 255lph, -6AN from filter-rail and rail-AFPR by Aeromotive, AFC, 2G MAS and 3" intake, Pocketlogger. Sold
    '92 AWD TSI: 6Bolt/4bolt (March), 2G MAS, Home made 3"=2.25" intake pipe. Ported O2 and amazingly uncracked 1G mani to 7cm, no cat, straight 2.5" in place of muffler. XTD 2200lb PP and 6pck sprung disk, Walboro 190, 550's, pocketlogger, ebay MBC, SAFC, MHI EIII16G.

  13. #13
    Join Date
    Dec 2003
    Posts
    210

    Default

    i would say get a test pipe and swap the cat on for emission tests.. you can get a cat online for 70-90 bucks online. you can even get them with 3" in/outlets

  14. #14
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    Sep 2003
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    Spain
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    Default i guess...

    ok, guys the test pipe seems to be the most popular here, so probably is what will i try to build.

    I assume that most of you have a test pipe installed in your car, please tell me how did you got rid of the rear o2 sensor CEL light?

    Maybe everybody have a dsmlink ECU?
    Mine is not a DSMlink and never will be, because it has no eeprom. And of course finding a used one is almost impossible here in Spain.

    Can anybody help me on the o2 sensor CEL thing?
    Thanks.
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  15. #15
    Join Date
    Jun 2003
    Location
    Freehold, new jersey
    Posts
    228

    Default

    I have a buschur 3" cat. I like it but I am sure it will clog like any others. I'll probably wind up punching it out anyway.
    But what is the deal with the cel? Do like I did and take the light bulb out, then you wont have to worry about the damn light.
    I'm the one who's gotta die when it's time for me to die. So let me live my life, the way I want to.

  16. #16
    Join Date
    May 2003
    Location
    Cleveland
    Posts
    716

    Default

    I think they make O2 simulators for it
    93 Dodge Colt. 708whp
    10.5@149mph. Retired @200mph

    87 Rx-7. 1st ever 4G powered @567whp

    89 Supra Turbo-Targa-White-Sex

    97 Tercel BlackHawk- "Mr Stinkypants"

    92 BMW 318i-Saturday Night Hoetaxi


    Don King for a Highway near you....

  17. #17
    Join Date
    Sep 2003
    Location
    Spain
    Posts
    1,482

    Default yes.

    Thanks, i found the schematics to "lie" the ECU about the 2nd o2 sensor on a post right below this one.

    Thanks.
    1991 Eagle Talon TSI AWD totally restored, rebuilt and upgraded.
    1992 Mitsubishi Eclipse GSX (Parts car)
    1997 Mitsu Eclipse GST (SOLD)

  18. #18
    Join Date
    Feb 2011
    Location
    3315 W Greenway Rd Phoenix, AZ
    Posts
    8

    Default

    Quote Originally Posted by KeltonDSMer View Post
    Stock cats generally get really clogged with crap, so I say any change would be a good change. You could also just find a cheap cat and use the straight pipe untill you must check the car's emmissions, then switch back.

    You have the muffler cut off right, with just a straight pipe? If you made a straight pipe for the cat too, it would support enough exhaust flow to run some more modifications without buying a standard exhaust.

    $300 for a Cat? Don't buy it...there are good ones for under $150
    Quote Originally Posted by mikyrc View Post
    I'm sorry coltboostin but you'r not right about they're the same. look at this picture:


    Our stock one doesn't have the "holes" that big. They have a kind of ceramic honeycomb or something like that with a very little holes.

    About a test pipe es better than any kind of cat i agree, but not all cats are the same.

    I write again my question, what will happen with the rear o2 sensor if there's a straight pipe instead of a cat? a CEL?

    Yes keltonDSMer, i took out the muffler that the previous owner put there and i welded a stright pipe with a splitted rear end.

    About the cat being so expensive i know it but it's because it has documentation that acredites that is under the laws of spain. We call this "homologado".

    If someone tells me how have no trouble with the rear o2 sensor i will go ahead and put a straight pipe instead of spending that money.

    Thanks to all.
    Cool! It is really fun reading this old threads in here i am really learning lots of info with regards to high flow catalytic converter. i am still undecided if high flow cats is really a best bang for the buck. i just wanna gain addtional hp on my ride. but if i decided to buy what will be the best brand to get??
    Last edited by masterjohnson; 03-03-2011 at 08:28 PM.

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