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Thread: Cat or Resonator Delete or BOTH??

  1. #1
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    Cat or Resonator Delete or BOTH??

    Hello All
    So im in the valley of decision. I want a better sound out of my 95 M3. I have an aftermarket exhaust (Stromung) on there now that sounds ok but it sounds too tamed. Im wanting a bit more louder throaty sound (not excessively loud). My car no longer needs emissions so Im looking to do this mod. Also Im wanting to make sure I make the right decision because I doubt you can back once you do the delete. So my question is which would give me the best sound that is not too loud..

    - Deleting the CATyltic Converter ??
    - Deleting the Resonator ??
    - Deleting BOTH cat and resonator ??

    Also what should I be looking at to pay to get this done??

    If anyone thats done this on a 95 E36 M3 or similar model I would love to know your experience. Also any input is appreciated.


    Thanks

  2. #2
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    I have the bimmerworld track/mid section that deletes the cats but uses a resonator instead and itís just enough more volume, so I would assume deleting the cats will get similar results.
    98 M3 sedan
    Custom CAI
    RK tune
    UUC fly - M5 clutch
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    Bilstein sport - H&R race

  3. #3
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    I installed a SuperSprint Euro system end-to-end with Race muffler, CAT delete, center resonator. I would not delete the CATs again. My system is plenty loud. I'm not sure about OBDI, but mine is an OBDII and I had to tune out the rear post CAT O2 sensors. The smell of a CATless exhaust is definitely different and, just for goodwill, I regret removing the CATs. I pass emissions in WA state but many other states I would fail.

  4. #4
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    are slow.
    Keep the cats and the resonators.

    Install an OBD2 midpipe, will be slightly louder and you'll gain 10-15hp.
    "Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."
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  5. #5
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    +1 for not deleting cats unless it's either FI and you're really going for max power output, or it's a track only car. Like Hova mentioned, OBD2 midsection is a good idea, and is an upgrade for you anyways. You can find a fairly cheap one off CL or something and try it out. I would hazard a guess it's not going to increase sound enough for your liking, but it's worth a shot. The next step would be a custom midsection with a resonator and high flow cat -- which is what I'm thinking I will do here soon.
    Last edited by Carpy2; 05-28-2020 at 11:09 PM.
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  6. #6
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    Didnít even think about going OBD2, thatís a great upgrade for little money. If you were closer you could have mine for free
    98 M3 sedan
    Custom CAI
    RK tune
    UUC fly - M5 clutch
    Stromung exhaust
    Bilstein sport - H&R race

  7. #7
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    Thanks for all the quick response guys. I have an appt with a reputable muffler shop in my area this Sat morning and wanted to make sure I have all my ducks in a row as far as info and being properly informed of what Im dealing with to make an educated decision on this. So just a couple more questions im not sure of. Im leaning more to what Hova suggested and based on all you other guys experiences i dnt think i would want to go the route of deleting the cats then. I definitely dont want that bad smell seeing as ill be using this car as daily on/off driver and on occasion some spirited hard driving.


    - Where can I get the OBD 2 MidPipe (What section of pipe does that replace exactly?? After the resonators or before the CATs??)
    - Im not sure what OBD my car is can someone help with that?? My car is a 1995 E36 M3.
    - How many O2 sensors does my car have specifically? 1 or 2??
    - My question is what if I just deleted the resonators?? (will that be louder or too loud relatively speaking)




    Also a friend mentioned that if i get the cat delete to make sure they dont take my CAT/resonators and to ask and make sure i get it back because theyre worth money and that the shops try to be slick and keep them. has anyone heard of this?




    Thx

  8. #8
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    Obd2 uses 2 primary 02 so you will have to chose one pipe for installation of the single 02 from your obd1 car. Stock 95 pipe merged into one and then back into 2, while stock 96-99 M3 pipe is two separate pipes. Ideally you would add a crossover pipe and put the 02 in it but you can also choose one bank.

  9. #9
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    are slow.
    Quote Originally Posted by Pfrederi View Post
    Also a friend mentioned that if i get the cat delete to make sure they dont take my CAT/resonators and to ask and make sure i get it back because theyre worth money and that the shops try to be slick and keep them. has anyone heard of this?
    They are worth $100-200 in scrap metal. I've sold quite a few downpipes/midpipes. Don't throw them away or let them keep it. If you do end up changing your mid section, cut 3-4" from each end of the cat and sell it. My last 95 M3 cat got around $150.


    Quote Originally Posted by Pfrederi View Post
    - How many O2 sensors does my car have specifically? 1 or 2??
    1 on the mid-pipe.

    Quote Originally Posted by Pfrederi View Post

    - My question is what if I just deleted the resonators?? (will that be louder or too loud relatively speaking)
    Lots of drone and rasp. Like a fart can.

    Quote Originally Posted by Pfrederi View Post
    - Where can I get the OBD 2 MidPipe (What section of pipe does that replace exactly?? After the resonators or before the CATs??)
    1996-1999 BMW M3
    1996-1999 BMW 328i
    Same exact midpipe.

    https://www.ebay.com/itm/BMW-OEM-E36...-/153783577302

    (not saying buy that one, but just an example of what it looks like).
    2 cats and 2 resonators.


    Quote Originally Posted by Pfrederi View Post
    - Im not sure what OBD my car is can someone help with that?? My car is a 1995 E36 M3.
    You are OBD1.
    And OBD2 midpipe bolts right up to the car, but you only have 1 O2 sensor on the midpipe, an OBD2 midpipe has 4 holes for O2 sensors. Just buy O2 plugs or weld them shut.

    https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1

    You also need to cut a hole and weld in a bung for your current O2 sensor. Really simple, anyone with a welder can do that for you. The above link is what I used, comes with all 4 plugs and some bungs as well.


    Differences between OBD1 and OBD2 midpipe. I probably have a picture on my phone, but that single merger goes into a 2 or 2.25" single hole and is a restriction in this system.

    x55xityvigu21.jpg


    BTW, come to think of it, I believe the OBD2 midpipe made my car sound deeper, but I'm not sure it was louder. It was quicker though.
    Last edited by Hova; 05-26-2020 at 02:43 PM.
    "Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."
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  10. #10
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    Try to find a local 96-99 owner who has one sitting around. Anyone who's built a track car or anything like that will have taken it out.
    Last edited by TostitoBandito; 05-26-2020 at 04:02 PM.
    1999 M3/2/5 - Titanium Silver - Track/Weekend Toy


  11. #11
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    Hey Thanks again gentlemen
    Ill see what the best route is for me to take if any. Seems like none of the options are worth it whether ending up in bad smell or just sounding god awful loud or just plain sounding horrible.

    Thx

  12. #12
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    Mine doesnít smell at all so Iím not quite sure where thatís coming from? Maybe that gets filtered out from the resonator in place of the cats.
    98 M3 sedan
    Custom CAI
    RK tune
    UUC fly - M5 clutch
    Stromung exhaust
    Bilstein sport - H&R race

  13. #13
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    You don’t notice the smell.

  14. #14
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    Quote Originally Posted by pbonsalb View Post
    You donít notice the smell.
    I know what smell youíre talking about and definitely have other cars without cats that do smell but I donít get that with my set up.
    98 M3 sedan
    Custom CAI
    RK tune
    UUC fly - M5 clutch
    Stromung exhaust
    Bilstein sport - H&R race

  15. #15
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    Quote Originally Posted by TheJordanWhitte View Post
    I know what smell you’re talking about and definitely have other cars without cats that do smell but I don’t get that with my set up.

    I think your nose is broken.

  16. #16
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    Some cars do smell more than others and the tune could be a factor. If you keep moving, you likely won’t notice. Stuck in traffic on a hot day in stagnant air with the windows down and it’s hard not to notice. I don’t spend much time under those conditions.

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