Removing The Cat !!!!
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  1. #1
    Fellow Frogger!
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    Icon4 Removing The Cat !!!!

    Having a 205gti which I will be using for club race days and driving on the street, what are everybodys thoughts about removing the CATALITIC CONVERTER. I know the standard gti exhaust system is pretty good as standard, so I dont want to stuff around with it if its not going to improve the breathing and power. the engine has been rebuilt using a JAZ head off a 405SRI and compression raised to 10.1 Would removing the CAT and putting in a straight pipe improve the performance ????. cheers.

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  2. #2
    Gone Fishin' Ray Bell's Avatar
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    I'd think the weight reduction alone would be a help!

  3. #3
    1000+ Posts tekkie's Avatar
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    Been told by Joe at Hi-Comp performance that the Supertourers tested the cats (they had to have them installed) and found the maximum of 1% reduction in power.
    For the sake of not having road compliant ( and possibly not class compliant - depends on track work you will be doing) car its not worth it. Just get a V6/V8 commodore cat converter.
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  4. #4
    Fellow Frogger! Cubits's Avatar
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    Is it ok to get a commodore cat? When i queried the guy at my local exhaust shop about it, he seemed a little confused. Then again, he looked confused when i said the word Peugeot...
    1987 205 GTI - Graphite Grey - 206k km's
    1988 MR2 Supercharger - Mica Blue - 114k km's

  5. #5
    1000+ Posts dino's Avatar
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    Putting aside all the moral arguments about the legality of removing cats of 205 gti...One thing is certain: removing the cat from a series 1 205gti....made a "big" difference....noticable power increase......Now I don t know if mine was buggered in the first place (I suspect most are well overdue for replacement anyway)...but geeezzzz...after removal...my 205gti could melt bitumen on the spot or for the next 50 meters....like I said ...noticable improvemnt....This one percent thing IMO just doesn t apply to aussie delivered 205gti....




    cheers



    dino

  6. #6
    1000+ Posts tekkie's Avatar
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    Catalytic Converter is just a can housing a honeycomb construction. Nothing else. The fins of the CC being very thin heat up and burn up all the exhaust nasties (not unlike the insinerators). Hence I am a little confused as to why any CAT cannot be replaced for any other CAT, size differentiations aside.

    As to why they clog up? Crap fuel, leaded fuel etc leaves particles on those honeycomb fins. After a while they will become restrictive. And every now and again CAT will fail if the honeycomb structure after taking a hit or two from your friendly speedhump collapses.

    Cubits, next time you are in the exhaust workshop ask them to show you 2 or 3 converers. And look down their guts. They should lok the same. The commodore cat used is designed in Australia and 1st used in VL turbo commodores. Up until the VY it was still basicaly the same unit. 2.5 inch free flow design.

    Dino, tsk tsk, mother earth says poo to you.
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  7. #7
    1000+ Posts dino's Avatar
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    SS.....enough said








    dino

  8. #8
    1000+ Posts tekkie's Avatar
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    Quote Originally Posted by dino
    SS.....enough said
    but since I have 2 cat converters its ok.


    .
    1300cc's of jap buzzbox delivered the times below.

    EC 1:54.6 , Wakefield 1:13.15 , OP (short) 52.00 , OP GP 1:24.40


  9. #9
    Moderator Alan S's Avatar
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    This cat business always gets me in.
    There have been a couple of owners in the UK with Cats on their cars which are models that came out where in some instances they were optional as a result, they find they can remove them without failing their bi-annual MOT (RWC) because the "book" shows them as optional on that prticular model, with the result some have taken them off and every time it seems to be the same result. Either no noticeable difference in performance; a slight loss of performance; or a loss of fuel economy. So I have doubts as to the wisdom of the move. I've no doubts our resident unenvironmentalist, Dino.... may have found a positive result if in fact his had collapsed, but when I have asked at the local exhaust shop, the owner of which races a V8 super street sedan at the speedway, he casually says "why bother, fit a universal one and it'll cost ya about 200 bucks." So you have to wonder if it's not a case of one size fits all rather than a horses for courses type of thing.


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  10. #10
    1000+ Posts dino's Avatar
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    our resident unenvironmentalist, Dino....


    hehehhe.........So I take it you r not a big fan of the 6.3 litre mercedes....

    On a more serious note.....I don t know what the benefit would be if any (performance-wise) when it comes to removing cats...This is why I specifically mentioned my car......I DID notice substantial improvement. FULL STOP and to be quite honest....No I dont think my cat had collapsed...as the car performed quite well before it....I 2 drove a few before I bought mine and if anything it was
    a better performing car than others......

    I m not going to "moralise" on the environmental issues,...thats a personal matter,....but ceartinly ALL is not always what it appears to be....ie my catless pug has been in pieces for quite a while now (not being driven) so its definitely been much more enviro-friendly than others that are driven on a daily basis.....
    But don t you guys/gals loose any sleep over it,....the 280 se has more than made up for it........cough cough cough....damn cigarettes.....



    cheers


    dino

  11. #11
    XTC
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    Don't know what states have them but I've seen mobile EPA testing. It looks like a Booze bus setup, the cops pull you over , the EPA sticks a probe up your exhaust and bingo ... Kinda like an alien abduction Deliberate removal of said CAT can cost you a bomb. So just fit a high flow jobbie.
    Quote Originally Posted by Dino
    I m not going to "moralise" on the environmental issues,...thats a personal matter,....
    It's a legal one actually, though one should have an environmental conscience of some sort (of varying degrees).

    - xTc -
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  12. #12
    1000+ Posts catshamlet's Avatar
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    Quote Originally Posted by Alan S
    This cat business always gets me in.
    There have been a couple of owners in the UK with Cats on their cars which are models that came out where in some instances they were optional as a result, they find they can remove them without failing their bi-annual MOT (RWC)

    Alan S

    Our MOT test is a once a year thing, for any car over three years old. I think this is only the second time that I know what I'm talking about. (The first was when I got Ray's year of birth as 70 B.C.)!

  13. #13
    Fellow Frogger! Cubits's Avatar
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    The mobile emissions testing usually targets cars that are visibly poor (smokey goes for smokey), or cars they suspect to be running a tad illegal (ricers). Unless your pug is running spinners and a bonnet scoop i think you'd slip past the radar (heck, noone notices my car at all!). :p

    But as stated above, just replacing the shagged out 18 year old cat with a high-flow would probably yield the same performance results without breaking emissions limits.

    If you were to take the cat out, what would you do with the lambda sensor (these things do have them, right?)?
    1987 205 GTI - Graphite Grey - 206k km's
    1988 MR2 Supercharger - Mica Blue - 114k km's

  14. #14
    1000+ Posts dino's Avatar
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    YES xtc.....You are right re: legality....but you ve got to appreciate the discussion from more than one perspective ie yours and mine and etc etc....
    My objection to being labbelled as an "UN-environmentalist" is rather lame and weak considering the number of members that drive cars that dont even have cats.....So, are all the 504 404 403 ds etc etc to be now classified as Anti enviro.......Give us a break......Do I now choose to dump the 505 because it carries the same moral offensive weight as removing a cat on a cat car......Yeahhh right.....

    Listen.....I am all for not stuffing around re. cat (ask baz)....and my recomendation is to stay within legal parameters.....but as often on this forum....issues get skewed....like the speeding thing....(are we alll killers now).....or the change the banner thread........somew things are best left alone....
    My comment was based on personal experience regarding the technical outcome.....
    Putting aside all the moral arguments about the legality of removing cats of 205 gti......was obviously not enough do deter the high morality commentary....This being in a technical and performance forum and alll................





    cheers


    dino

  15. #15
    Fellow Frogger! Cubits's Avatar
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    That's a lot of dots.
    1987 205 GTI - Graphite Grey - 206k km's
    1988 MR2 Supercharger - Mica Blue - 114k km's

  16. #16
    Fellow Frogger!
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    Quote Originally Posted by Cubits
    That's a lot of dots.
    Guys, guys Im sorry i asked the question now !!!. Can we forget all the legal and moral statements, OK then Im going to take the car off the road and only run on the track, there is that better!!!. Now where were we, Oh yes, do you think the car would get a power gain by removing the CAT ??. Simple question.......... ?

  17. #17
    1000+ Posts dino's Avatar
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    In my opinion.......................................YES




    cheers


    dino

  18. #18
    Fellow Frogger! bazgti's Avatar
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    Quote Originally Posted by maxie
    Guys, guys Im sorry i asked the question now !!!. Can we forget all the legal and moral statements, OK then Im going to take the car off the road and only run on the track, there is that better!!!. Now where were we, Oh yes, do you think the car would get a power gain by removing the CAT ??. Simple question.......... ?

    you will increase the power of your car with the cat off.however dont drive it on the road unless you can afford the $6000 fine or the $20,000 fine for the guy who took it off.
    if you need to replce it put a v8 commodore high flow cat on.i have one on my 205 gti and it works well with added bass note.
    i was going to piss mine off until my mate got caught and went for the $6000 booby prise.
    not sure of legalities entering club rallys or motorkhana's withouit cat.
    i think the car is supposed to be fully roadworthy.
    in the uk they dont have as strict emission standards as we do in green australia so they can run without the cat.
    alot of the uk import 205 gti's are catless.-BAZZ

  19. #19
    1000+ Posts tekkie's Avatar
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    Quote Originally Posted by maxie
    Guys, guys Im sorry i asked the question now !!!. Can we forget all the legal and moral statements, OK then Im going to take the car off the road and only run on the track, there is that better!!!. Now where were we, Oh yes, do you think the car would get a power gain by removing the CAT ??. Simple question.......... ?
    Simple Answer
    as my 1st answer stated, 1% improvement between new CAT or no cat. There clear enough? (your old CAT will most probably more then 1% loss btw)


    on the brighter note, if you ask a question on AussieFrogs expect a debate. Its upto you to either slef filter out the moral discussions or to join them and take the tech details along the way.
    .
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  20. #20
    1000+ Posts Stone Free's Avatar
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    Rachs's 205 has the cat on it still, but the previous owner stuck a tube through it so basically it LOOKS like it has a cat, but the exhaust pipe goes right through it.
    The AWARD WINNING 1998 Blaze Yellow 306 GTi6


    ......and a Series 3 205GTi on the side.



    "I enjoy telling people what to do, because I am an arrogant rock star. That's what I do. That's my job." Gene Simmons, ROCK SCHOOL.

  21. #21
    Fellow Frogger! casnell's Avatar
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    Quote Originally Posted by bazgti
    not sure of legalities entering club rallys or motorkhana's withouit cat.
    i think the car is supposed to be fully roadworthy.
    .-BAZZ
    Yes rally cars are supposed to run with cats, even at ARC level , but I'm yet to see one, esp at ARC 's! Although running anti-lag and a cat don't go together at all...
    205gti

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