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S3 DE-CAT

Discussion in 'A3/S3 Forum (8L Chassis)' started by MOSSY, Apr 1, 2005.

  1. MOSSY

    MOSSY Member

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    Has anyone had just a de cat fitted to there S3???

    Iam wanting to know if there was a noticeable difference in the car. I noticed a big difference when I had the EVO.


    Cheers

    Mossy
     
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  3. MOSSY

    MOSSY Member

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    Pure,

    Iam not saying your wrong here but have you seen the inside of a cat, they must be so restricted compared to a straight through section. I would of thought a de cat would have been a better improvement than a after market exhaust would do.

    As I said before I noticed a hell of an improvement when I did this on my Evo. I dont understand what the difference is here, maybe ess3 can tell us.

    Paul,

    I know doing this mod is illegal, so is speeding but we all still do it. You take a chance.

    Do you know which cars have the twin lamba sensor, I have been told the sensor will be fitted back in.

    Thanks all, hope i havent upset anyone here, I didn't mean to.

    Mossy
     
  4. pure

    pure Member

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    U can see right through the S3 cat, there not that restrictive, honestly.
     
  5. dickys3

    dickys3 Moderator
    Staff Member Moderator

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    As PAul and pure say, the S3 cat is not restrictive. Don't waste your money!
     
  6. monty77

    monty77 Member

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    S3 cat design is a good one. Twin cats in parallel, 1/2 the restriction in theory. Manifold/gutless turbo at high revs are where the largest gains are to be made.

    A
     
  7. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    Who told you that you can see straight through the S3 cat ?


    [/ QUOTE ]

    Me, for one...


    [ QUOTE ]

    Rubbish.


    [/ QUOTE ]

    You need glasses.


    [ QUOTE ]

    They are 400 cpsi. Chop the cats off the pipe ,so theres nothing to deflect the light, and at the right angle you will see daylight. But not clear daylight.


    [/ QUOTE ]

    So you can see through them then?
    I think so...

    They are not restrictive...end of chat.

    You can see daylight through them...you can see people, cars, birds in the sky etc, if you happen to be looking in the right direction.

    Being able to see things through them means to me there isn't too much of a restriction.

    I agree that 100 cell cats are easier to see through...almost as if there is nothing in them!


    [ QUOTE ]

    Having said that, the point you make about them not being restrictive is true. Put a single Rossi 100cell cat on mine. TBH didn't make much difference at all ,and you can read a car number plate through it ! Hopefully pay dividends when I swap the turbo.


    [/ QUOTE ]

    ...and I had twin 100 cell cats...and gained precisely nothing...dyno proven before and after.

    Some of the Japanese car cats are more restrictive...you cant see daylight through a UK spec Honda ITR cat...but you can the Jap spec version of the cat (which also happens to ba a larger bore)...

    But on the S3, as with most VAG cats...there is nothing to be gained.

    You can see through a Mk3 Golf GTI cat too...
    Changed that to a 200 Cell single...which you can also see thtough (strangely enough!)...and gained ...nothing. Again dyno proven.

    VAG cats are efficient...and legal.
    ...and you won't throw a check light.

    Waste of money.
     
  8. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    ess 3, Fair enough point, you dont get any diff between S3 cat and performance cat. Have you actually tried the car without a cat????


    [/ QUOTE ]

    Check light!!

    I must admit, I've not de-catted mine...I wouldn't.
    I can't be arsed with the fine / agro should I get caught, the hassle of swapping for the MOT or the check light...
    I have seen plenty dynod...and all gained nothing...on reliable dynos with non-biased operators.

    If you've looked at a Milltek 100 cell sports set of cats...they are virtually empty...there is no restriction!!
    What's the point?

    [ QUOTE ]

    As for it being a waist of money, it's only gonna cost me £65 to get a replacement section made up.


    [/ QUOTE ]

    ...and the hassle?
    ...potential fine?
    ...pain of check light?

    Honestly, if you canm't tune the damn thing to remain legal...don't bother...that's my philosophy.
    All my tuned cars have remained 100% MOT compliant...there is no need to remove the cat, as you gain nothing.
    That's my view.
     
  9. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    Ok guys, I don't know much BUT, what about instead you fit a Milltek Sport Cat, performance gains are supposed to be good, (or so I've heard):



    [/ QUOTE ]

    You heard wrong.

    I got NOTHING out of my set...except a bill for £800.

    You don't need to change the cats on an S3 except perhaps in extreme tuning circumstances...

    Save the cash...buy something else that adds something quantifiable.
     
  10. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    ess 3, Fair enough point, you dont get any diff between S3 cat and performance cat. Have you actually tried the car without a cat????


    [/ QUOTE ]

    One more thing...

    Do a search on the subject...

    Anyone who is honest and willing to look at things onjectively will tell you that a de-cat gave them nothing power wise.

    Many do get an engine check light.

    Many remove the de-cat soon after fitting...

    Sports cats also add nothing....this has also been proven many times.
     
  11. MOSSY

    MOSSY Member

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    Out of interest ESS 3 what have you got on yours???

    Maybe I will save money and put it towards Ecu remap/wheels

    Does anyone know the diff in weight of these rs4 reps compared to Avus wheels???

    Cheers again
     
  12. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    Out of interest ESS 3 what have you got on yours???


    [/ QUOTE ]

    Milltek sports cats...was 100 Cell when I owned my S3...sold the car to David R (on here)...and it now has Milltek 200 Cell cats.

    ...which also made no difference.

    [ QUOTE ]

    Maybe I will save money and put it towards Ecu remap/wheels


    [/ QUOTE ]

    I suggest you'll be quicker everywhere buying a set of Brembos instead of the cats - at about the same price.

    [ QUOTE ]

    Does anyone know the diff in weight of these rs4 reps compared to Avus wheels???


    [/ QUOTE ]

    Heavier I'd expect...certainly if you go to 18s.

    My 17 Avus were a similar weight to my 18" 2pc BBS...which are a light wheel.

    Certainly in 18"...the RS4 trye replicas are heavier than 17" Avus...and to gain handling you need to go to 18s.
     
  13. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    Ess_Three,

    As "Catmeister", I would appreciate your opinion on this one.


    [/ QUOTE ]

    I'm no expert...
    I'm only trying to save people money by pointing out the bs associated with many of the power claims listed for Cat swaps / De-cat swaps...

    At the end of the day, I couldn't really give a toss what others do...but if I can save someone from making a potentially expensive mistake...that'll do for me!


    [ QUOTE ]

    I believe the situation regarding legality with diesels is different. (Comments written in Audi Driver). The law at MOT time requires a smoke test not a gas analysis. That is why the recommendation is to take your car up the motorway for a clear out before the test. Also There is no Lamda sensor on a diesel cat so no check light problems.

    Removing this possibly combined with a free flow exhaust reduces back pressure and spooling time. Acceleration/mpg improved. Top speed remains the same. The turbo takes out a lot of noise anyway so a less restrictive exhaust is not always noisier...

    Whats your thoughts?

    Rick

    [/ QUOTE ]

    I'd love to comment...but i've never had any dealings with diesels, tuning them, or the law regarding them. Sorry...I'm not much use here.
     
  14. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    @ Essthree, You chopped the cats out of the pipe then did you ?
    As my post said , fitted the single 100 and made no noticable difference.


    [/ QUOTE ]

    No...the car in question has run with standard cats, 100 cell cats and now 200 cell cats (as the 100 cell versions kept bringing on the check light!!...so what will NO cats do?)

    No power differences were measured from step to step...

    Hence my view (scientifically proven) that the cats are not restrictive, and will not add power.

    This was on a car running 280BHP/330 lb-ft BTW...so it's working the cats hard!


    [ QUOTE ]

    I think we have our own versions of 'straight through'.


    [/ QUOTE ]

    Straight through is straight through.
    Nothing in the way...no torturous path, just a straight run, which you can see through...like the cats (including standard!)

    That's my interpretation...


    [ QUOTE ]

    But as I said, no restriction unless using a bigger turbo.


    [/ QUOTE ]

    This may well be the case...but again, it's never been proven.
     
  15. Ryanc

    Ryanc Active Member

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    I'm sure i heard of someone melting the cat with a big turbo,anyhow it's not worth the risk with a BT.I think mtm big turbo,comes with a sports cat?
     
  16. Defratos

    Defratos You’re Dethpicable!!

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    yeah it does, but hey guys, I'm curiouse, how much roughtly is a big turbo and labour costs?
     
  17. Ryanc

    Ryanc Active Member

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    mtm is about 8k
    Have a chat with jbs as there doing a bt for the tt/s3 will be around 4k.
     
  18. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    I'm sure i heard of someone melting the cat with a big turbo,anyhow it's not worth the risk with a BT.I think mtm big turbo,comes with a sports cat?

    [/ QUOTE ]

    Generally, conversions come with a single sports car as it's cheaper and easier to make another single cat work, than to make a new downpipe fit and work with a standard cat.

    I agree that a free flow cat is wise if going with a big turbo...


    But let's get something cleared up...a 100 Cell sports cat isn't going to restrict flow to any significant degree, if it's sized correctly.

    On a high output S3, you will see no meaningful gain from changing the cats...to a lower cell per square inch filling...

    Nothing from removing the cats...except making a legal car illegal, and giving you a potential check light.

    As for cats melting at very high power outputs...I could see this being possible...with 400 cell or higher cats...but I've never actually heard of one geniune case - lots of "my brother's mate's uncle one heard about...", but nothing concrete.

    Free flow cats are good insurance...and on a BT S3 perhaps thay will allow the engine to make more power if mapped correctly...but on a standard turbo'd S3...they are not worth the money.

    ...and that's from someone who has spent the £800 buying them.
     
  19. Ryanc

    Ryanc Active Member

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    I totally agree with you glen,my sports cat cost me £250 so alot of these companies are ripping people off.Hows the porkka going?
     
  20. Grant

    Grant Well-Known Member
    VCDS Map User Audi RS3

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    I have a Supersprint de-cat and it makes no difference!

    The only thing you gain is a little 'pop' when changing from 1st to 2nd.
     
  21. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    I totally agree with you glen,my sports cat cost me £250 so alot of these companies are ripping people off


    [/ QUOTE ]

    Too true...
    Both in what they charge, and what they claim for power gains.


    [ QUOTE ]

    .Hows the porkka going?

    [/ QUOTE ]

    /ubbthreads/images/graemlins/woohoo.gif

    It's sublime...the brakes have now bedded in...the gearchange loosened up...the suspension settled...and the engine starting to rev more freely.

    Goes sidewards all together too easily though...just ask Grant!
    I still have his handprints in the side bolsters of my passenger seat from the RR day! /ubbthreads/images/graemlins/grin.gif

    It makes 320BHP on the dyno with only 1000miles on it...
     
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  23. Ess_Three

    Ess_Three Active Member

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    [ QUOTE ]
    I have a Supersprint de-cat and it makes no difference!


    [/ QUOTE ]

    Nice one Grant...another adding weight to the fact that the cats / de-cat don't make any difference on an S3.


    Do you get a check light rant?
    With yours being an early S3, you may get away without the dreaded check light...
     
  24. Grant

    Grant Well-Known Member
    VCDS Map User Audi RS3

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    [ QUOTE ]
    [ QUOTE ]
    I have a Supersprint de-cat and it makes no difference!


    [/ QUOTE ]

    Nice one Grant...another adding weight to the fact that the cats / de-cat don't make any difference on an S3.


    [/ QUOTE ]
    Glad I could help!

    [ QUOTE ]

    Do you get a check light rant?
    With yours being an early S3, you may get away without the dreaded check light...

    [/ QUOTE ]
    I get no problems with check lights because I have an early S3 and therefore do not have the after cat sensor.
     
  25. PaulJC84

    PaulJC84 Owner

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    The decat on my A4 made a small difference just revs freely. Only cost £100 so not quite as pricey as the S3 setup!! The single standard cat on the A4 is pretty clogged up. My car now puts out loads of fumes if you were to have a puff of it, it would about knock you out!!

    Cheers just thought i would add my pennies worth cos i know a lot of the A4 folks read the other forums.
     
  26. s3bow

    s3bow Member

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    @ EssThree, I remember you saying about the check light before. I haven't had one yet and curiously no fault code either. I was expecting one. Maybe the cat is still too new .

    Chris.
     
  27. davyb69

    davyb69 New Member

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    Ive got a supersprint decat as well.......rubbish, no difference whatsoever apart from the annoying light now.

    Its coming off next time im under it.
     

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