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S52 Swap - E30 or E36 Cat back?

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    S52 Swap - E30 or E36 Cat back?

    I'm planning a S52 swap soon and want to know which cat back to buy.

    I've already ordered the 2 x 3 into 1 headers and want to know what cat back to get. My biggest concern is proper fitment. There's gonna be a E36 M3 5 speed for mounting, but in back its still gonna be all E30....


    Thoughts?

    #2
    E30 pipes are too small and the E36 catback is not going to fit. A lot of people say they do fit but "fit" for some people is a much more loose term than others - to me it means it fits where it's supposed to and the pipes follow the heat shield and don't rub anything, not just I can get it to hang and not fall off. Get a muffler or catback of your choosing, something that's suited for the engine (ie an E36 performance exhaust), and if you want to run cats, get a Magnaflow cat(s) - they're cheaper than what people sell E36 midpipes for used, and flow hella better. Then crack open the piggy bank and get an exhaust shop to do the rest, it's the only proper way to do this.

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      #3
      Originally posted by BigD View Post
      E30 pipes are too small and the E36 catback is not going to fit. A lot of people say they do fit but "fit" for some people is a much more loose term than others - to me it means it fits where it's supposed to and the pipes follow the heat shield and don't rub anything, not just I can get it to hang and not fall off. Get a muffler or catback of your choosing, something that's suited for the engine (ie an E36 performance exhaust), and if you want to run cats, get a Magnaflow cat(s) - they're cheaper than what people sell E36 midpipes for used, and flow hella better. Then crack open the piggy bank and get an exhaust shop to do the rest, it's the only proper way to do this.
      The e30 cat will work but is not optimal. You'd lose a few ponies with it. The e30 muffler section is the part that is terrible, you'd at least want to upgrade that.

      The e36 cat section works great, especially the OBD2 stuff. For some it's a direct bolt on but more than likely it will take some slight modification. Most of the modification is where your headers are, anyway. From the headers back they'd fit just fine with no modification.

      It will fit. Mine fits as well as stock ever did, no rubbing weird stick-out or anything.

      It's heavier but no one has ever complained about a tinny or raspy sound from it.

      A competent exhaust shop will do a good job too, especially if you know what you want them to install.

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        #4
        so could i use a full e36 ODBI m3 exhaust on an e30 with minimal modification? I ask this because in order to register my car it has to pass referee. I have been told that they want you to use stock cats and exhaust mani. After i get the CARB sticker i would change all that though.
        -Alex

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          #5
          Originally posted by Uber E30 View Post
          so could i use a full e36 ODBI m3 exhaust on an e30 with minimal modification?

          Yes, this was discussed recently... http://www.r3vlimited.com/board/showthread.php?t=138692

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            #6
            awesome thanks for the info
            -Alex

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              #7
              Originally posted by hoveringuy View Post
              From the headers back they'd fit just fine with no modification.

              It will fit. Mine fits as well as stock ever did, no rubbing weird stick-out or anything.
              An excerpt of your own post from the thread you linked:

              Originally posted by hoveringuy View Post
              It will fit, but it's not a "drag and drop" bolt in, IMO. I had to make a few cuts to the OBD2 mids to make them clear the sway bar and the stock suspension lollipop. If you have the Treehouse CABs and shim the engine it may bolt in as-is.

              I also had to remove heat shielding to get it to tuck, but now it fits nice and snug.
              Once again, I have to really emphasize this to people who are going through the swap for the first time: take this "it will fit" stuff with a massive grain of salt. If you're expecting to just bolt flanges together and maybe do a little hammering, IT WILL NOT WORK. I was in your shoes as well, and was also told by a lot of people that it will fit, while others just vaguely said they paid for custom piping. I wasted a lot of time getting annoyed with the midpipe trying to get it to fit cleanly - wasting a lot of time in an effort to make it easier, however paradoxical that may sound.

              Finally I took it to the exhaust shop who said the whole midpipe is a waste of time. They cut one OBD2 header to point back more, so now I don't have to jack up the engine to remove the pipes. And they made me custom stainless piping all the way to the muffler.

              I know it's most convenient to listen to what makes you feel good but for what it's worth, I say budget a good chunk of change in your swap for exhaust work, at least a grand if you want good work and stainless.

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                #8
                Keep in mind, he was also asking about what to put behind a set of headers and about 95% of the fitment issue with the OBDx mid sections is between the sway bar and the CAB. I am currently running mine all the way up into stock OBD2 headers and needed to modify the mid sections because it had to clear that stuff.

                With headers, this will still need to be dealt with except the headers get modified, not the mid section.

                Neither one is going to fit perfectly out of the box.

                I think finding the right muffler shop is a crap shoot. They would all rather fabricate an exhaust from scratch than mess around with modifying old exhaust parts.

                I've seen some great fabricated exhausts and I'm sure they cost a grand, but I don't think that it's a prerequisite for the swap to any degree. I've also seen a lot of "I got my exhaust back from the shop and it sounds like a Hyundai" threads. How do I fix it?

                My total investment for a nice sounding exhaust was $50 for OBD2 headers, $100 for an OBD2 mid section, $75 for an M3 muffler and $40 for hardware. Oh yeah, and some work.

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                  #9
                  Thanks for the advice guys.

                  Comment


                    #10
                    Originally posted by 91E30-318is View Post
                    Thanks for the advice guys.
                    You'll get different answers from everybody on this, fer sure. One thing I noticed at the e30 picnic was the wide variety of exhausts. A lot of the cutom fab stuff was fairly loud.

                    I do have a set of ebay headers in the mail, I was relatively impressed with how well they fit on about 4 cars I saw with them. I will let you know how mine go in and how they match up to my OBD 2 mids.

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                      #11
                      Old thread but hoping to to figure this out..

                      I have an S52 swap sitting at the exhaust shop right now to have the donor car's M3 exhaust installed onto it.

                      They are telling me that the front header has clearance issues and they'll have to cut and angle the header in order for the downpipe to bolt up. Has anyone else experienced this? I can't find anything about it when searching
                      sigpic

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                        #12
                        Originally posted by rcfanatic View Post
                        Old thread but hoping to to figure this out..

                        I have an S52 swap sitting at the exhaust shop right now to have the donor car's M3 exhaust installed onto it.

                        They are telling me that the front header has clearance issues and they'll have to cut and angle the header in order for the downpipe to bolt up. Has anyone else experienced this? I can't find anything about it when searching

                        I will be sending my car to the exhaust shop in a month or so. My front manifold has the exact same issue as yours - not enough angle and clearance where it sits by the subframe. I was already assuming I'd have to have a custom exhaust done, so I'll probably have them make the necessary mod to the front manifold as well. I'm not interested in shimming the motor mounts as it may adversely affect the alignment of the driveline.
                        -Geno

                        '87 325is (s52'd)
                        '95 525iT
                        '02 Range Rover 4.6 HSE
                        '98 Disco 1

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                          #13
                          Yes the stock s52 headers will not clear the subframe and sway bar so they (actually just one I think) will have to be cut. You will also have to make another couple cuts to get the exhaust to hang close to the body. If you don't it'll hang kind of low.


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