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Thread: e34 540i Catalytic converter options

  1. #1
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    e34 540i Catalytic converter options

    I had a shop tell me one of the cats is bad. There is a rattle I hear from under the car so I'm guessing that's the catalytic converter.

    So assuming the issue is the cat has anyone had any luck with aftermarket cats? Or used/remanufactured? The brand new OEM ones are >$1k a piece so I'm balking a little at paying that but will if it's the best option. I've been doing some searching and it seems a mixed bag for whether or not aftermarket ones work well or last.

    Anybody with a 540i have any personal experience?

  2. #2
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    Yeah, it's not worth it to go OEM on cats, even with cheaper cars like Mazdas or the like.

    My 540 has what appears to be Magnaflow cats, they are probably higher-flowing than OEM and fast-pass Colorado emissions. You basically need a good muffler shop.
    - Brent
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    Quote Originally Posted by danespann View Post
    Every E34 needs the same things in the end.

  3. #3
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    I had mine gutted. Haven't had any issues. OEM Cats are very expensive.

  4. #4
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    ^That option is great*

    *providing you don't need them for emissions.
    - Brent
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    Quote Originally Posted by danespann View Post
    Every E34 needs the same things in the end.

  5. #5
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    OE cats are expensive for a reason, they have MANY times more precious metals that do the catalyzing so work better and last longer.
    My advice is to find and use good OE cats.
    Your dead cats are worth more in scrap than NEW aftermarket ones cost. Nice racket for the muffler shops.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  6. #6
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    As a Californian, the cost on catalytic converters is cataclysmic. I just replaced one on my wife's Jetta for $261 and it was a generic Walker; the rest of the country pays $85 or so. OEM was like $700. On a car that isn't worth more than $2K, going OEM doesn't make sense.

    My 540i has aftermarket cats and somehow passed California emissions. I would go cheap if it was me. Expensive enough to do what you need to do but no more.

  7. #7
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    Quote Originally Posted by marshallnoise View Post
    the cost on catalytic converters is cataclysmic
    +10 points
    - Brent
    www.angry-ass.com

    Quote Originally Posted by danespann View Post
    Every E34 needs the same things in the end.

  8. #8
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    PM me. I have solution for you.


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  9. #9
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    Quote Originally Posted by NikosX View Post
    PM me. I have solution for you.


    Sent from my iPhone using Tapatalk
    Sent you a PM.

    Thanks for the replies. I'm leaning towards going with aftermarket cats. In my state we only need emissions tests when the car is first titled so it's not like I'm particularly worried but if I sell the car at some point I'd like the next owner to not have any issues with inspection/registering the car. But seems people have been able to pass emissions tests with the Magnaflow cats at least.

    As far as I know only one of mine is bad but should I replace both just so both sides have the same cat?

  10. #10
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    I had a pair of 13" magnaflow universals on my car when it was b40/6spd and they did NOT pass CT emissions, no matter what i tried. They were a couple years old at that point, but the car DID pass emissions with the factory b30 cats still fitted to the b40 about 2yrs prior (that were 200k miles old at that point). I do not know how maryland emissions compare.
    Last edited by AHenry014; 02-24-2017 at 12:51 PM.
    -Alex

  11. #11
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    Quote Originally Posted by jumpshotjonny View Post
    I had a shop tell me one of the cats is bad. There is a rattle I hear from under the car so I'm guessing that's the catalytic converter.
    Why would the cat be bad if it only has a rattle?

    In CT, I've passed twice already with my $50 magnaflow cat. The cat is now 3 years old so we'll see if it still passes next time. I don't see why not.
    demet

  12. #12
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    Quote Originally Posted by demetk View Post
    Why would the cat be bad if it only has a rattle?
    Because when it breaks apart internally and begins rattling, the catalyst has cooked so hot it cracks into pieces- this happens due to over pollution of the matrix and/or extended hot conditions due to prolonged rich running.
    Last edited by ThreeM30s; 02-24-2017 at 09:49 PM.
    Got LSD, Megasquirt coming... and a few manual 'gearboxen'. The M50 should be done this week.

  13. #13
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  14. #14
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    Is there a high flow cat for 525i?

  15. #15
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    Yes. There are examples mentioned in this very thread.... (?)
    Also, e34s don't need cats in NY period, fyi. (Not saying you shouldn't use them, as a NY'er I've always kept them on my OBD1 cars anyway para la tierra. . .)
    Last edited by bigsixe34; 08-10-2018 at 05:00 AM.


  16. #16
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    Do E34 have aftercat O2 sensors? Just saying because I did put Magnaflows on E39 540 I had before and check engine would come up for cat efficiency.

  17. #17
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    No they do not. The change from e34 to e39 and OBD 1 to OBD 2 was simultaneous for 1996. OBD 1 can't tell you if your cat works or not.


  18. #18
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    Any good exhaust shop in the nyc area you would recommend

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