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a few decat pre-purchase questions .........

Discussion in 'A3/S3 Forum (8L Chassis)' started by jc_1989, Jul 19, 2011.

  1. jc_1989
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    jc_1989 Member

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    [Jul 19, 2011]
    hi all, i am looking to buy a decat for my 2000 210bhp S3 and had a couple of questions.

    firstly, would the same decat pipe fit all S3's built between 99-03 no matter what engine is fitted?

    also, will i have engine management issues? my car already has an air filter, backbox and re-map fitted.

    any help much appriciated!!! :thumbsup:
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  3. superkarl
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    superkarl MAN OF STEEL

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    [Jul 19, 2011]
    Yes, all the same turbo therefore all the same downpipe.

    You may, and most likely, will have an engine management light on with a decat, because your post cat lambda sensor will be reading that the cats are ****ed (because there isnt one). It can be mapped out tho, and there are spacers so that the sensor is out of gas flow slightly, which according to some people doesn't bring the light up.

    May I ask which dp your going for?
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  4. jc_1989
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    jc_1989 Member

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    [Jul 19, 2011]
    ok cool, i havn't decided which decat yet, was just looking for a basic decat really. nothing too expensive like a sports cat, moneys a bit tight lol. will it run/idle rough with a decat if the engine management light comes on? i presume it will put the fuelling out?
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  5. superkarl
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    superkarl MAN OF STEEL

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    [Jul 19, 2011]
    No wont affect fuelling, pre cat lambda controls that, if you have one, I think.
    Oh so just a decat on its own. If im honest there isn't much if any benefit from that, your downpipe and decat will still be two small pipes before it goes into one.
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  6. jc_1989
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    jc_1989 Member

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    [Jul 19, 2011]
    i thought if there wasnt a cat in the exhaust then there would be less exhaust gas restriction, and so make a better air flow through the engine and so improving performance?
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  7. Andrew@A.L.D
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    Andrew@A.L.D May add NOS to 600+bhp?

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    [Jul 19, 2011]
    It will affect the fueling as the gasses are passing the lambda faster not getting a proper reading as its when the the cat is fitted the gasses are slowing down trying to pass though the cat
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  8. jc_1989
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    jc_1989 Member

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    [Jul 20, 2011]
    so basically, is a decat a waste of time with the mods i already have? or will it improve performance? will i need to do anything more once the decat is fitted or will the engine management sort itself out?
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  9. A3tell
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    A3tell Member

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    [Jul 20, 2011]
    to get the most flow gains, you would need a bigger dp with the decat! the dp is the more restrictive part!
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  10. jc_1989
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    jc_1989 Member

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    [Jul 21, 2011]
    i would have thought the cat was more restrictive than the downpipe as its full of baffles.....
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