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Trying to quiet this thing down once and for all

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    Trying to quiet this thing down once and for all

    So my 325i came with a rusted out cat back with rusted out hangers. I had a shop install a 2.5" inlet Vibrant Streetpower muffler with 2.5" single piping to 2 in-line 2.5" Vibrant Ultra Quiet resonators in place of the cat with a kinda-sorta Y-pipe (first pic below) installed leading to the factory mid pipes before the down pipes. It's definitely quieter than the rusty boi but it's still pretty loud at low speeds and drones too much (any drone is too much for me).

    It sounds like there might be an exhaust leak in the section between the cat and the downpipes (second pic below) because when accelerating from a stop, there's a metallic/hollow/rattling-kinda sound coming from the firewall area and my girlfriend said she could smell something coming from the car when she was in front of it. I tried to test for a leak with a leaf blower blowing through the muffler and I think there's air moving from that section but on top so I couldn't see for sure (I felt around the manifolds, downpipes, and O2 sensor but nothing there).

    I have a Flowmaster 2.5" metallic 200 cell high flow cat (https://www.jegs.com/i/Flowmaster/389/2000125/10002/-1) lying around and am thinking of having the shop chop that oem x-pipe(?) section off and weld the cat in place of it with 2.5" piping leading back to the resonators and weld the y-pipe in after the cat just before the downpipes,


    My main question is this: even if there's no exhaust leak and the setup is just loud, would the cat in place of this section quiet the exhaust note much, especially at lower revs? I thought the 2 resonators would be enough but I hate how loud it is I can't stand the drone, especially since I haven't 5-speed swapped my car yet and I feel like I'm just like one of the loud, automatic Hondas that plague these Tampa streets.


    Thank you for reading my novel and I appreciate any input




    1990 E30 325i sedan - Gletscherblau (280) over Indigo cloth (0271)

    #2
    Remember one thing: the smaller it is, the more noise it will produce.
    Also, the larger it is, the more noise will be suppressed (absorbed).

    The stock cat isn't just a cat. It's also has a built in resonator, with a layer of insulation wrapped under the outer shell.
    There's a lot going on with the stock setup to keep these cars quiet and drone free.

    This is why it's imperative to purchase QUALITY parts. Not some universal junk that's discounted and designed for universal use.
    If you don't want your car to sound like a ratty 90's Civic, you need to spend the money.



    If it's got tits or tires, it's gonna cost ya!

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      #3
      I would install a factory cat section and mate it to an IE Catback and be done with it. The IE catback used to be available on eBay for a good bit cheaper, but I haven't seen it on there lately.

      This setup is quiet, drone free, and sounds great when you open it up, just a little louder than stock.


      1989 Zinnoberrot M3 Build Thread
      1990 Brilliantrot 325iS Build Thread

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