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    S54 Swap Exhaust systems

    What's everyone running, Single pipe vs dual?

    I want to make something that's quiet, and wont lose alot of torque (keep reading mixed answers on single exhausts).

    Seems alot of the track orientated swaps go for a single 3", sacrificing some lower end torque but all for the weight reduction over a dual system - Do you even lose much?

    The Kassel swap info I read through says 2.5" is fine, I already have one left over from my M52 but if I am better off going 3", or a dual system I'm all for it.

    Preferences / Experiences?

    I'm kinda torn between Arc Asylums 3" system or doing my own 2.25 dual with some Borla mufflers.. Not after anything loud, it will be street mainly but will definitely see the track every so often..

    #2
    if you already have a 2.5" system, I'd start from there and see how you like it.

    there is power to be gained with a 3" or even 3.5" but there's usually an associated torque loss that comes with it as the scavenging velocities can be lower. this is highly dependent on header design though.

    personally I would stick to a single either way just due to the decreased weight, cost and complexity. if you don't want it to be loud, use 2 mufflers - one where the cat would have gone and another in the traditional location. it won't hurt power but it will mellow it out a lot.
    Build thread

    Bimmerlabs

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      #3
      I suspect that smaller diameter exhausts are also quieter.

      And if you really want quiet, you're going to need serious muffling. Dual mufflers barely get you to tolerable with the good engines, IMHO.
      2006 GMC Sierra 2500HD 4WD LBZ/Allison
      2002 BMW M3 Alpinweiß/Black
      1999 323i GTS2 Alpinweiß
      1995 M3 Dakargelb/Black
      - S50B32/S6S420G/3.91
      1990 325is Brilliantrot/Tan
      1989 M3 Alpinweiß/Black

      Hers: 1996 Porsche 911 Turbo Black/Black
      Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

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        #4
        the length/size of the muffler also affects sound. the larger, the quieter - but also the heavier and more expensive.
        Build thread

        Bimmerlabs

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          #5
          I am using Ebay headers into a modified (US) Section 1. The Section 1 has the resonator removed and merged probably on the order of a foot earlier than the crossover on the US Section 2.



          It is then merged with a 2.125" to 3.5" Burns Y megaphone, to a 3.5" dual muffler system.



          My exhaust was mostly fabbed because of convenience and wanting to tuck the 3.5" pipe into the center tunnel of the car. There still isn't that much ground clearance. The system is fairly loud, but it's less than 100 dB at WOT. The rear exhaust is a 5x11x22 Magnaflow 14909. I wanted as large displacement muffler as possible in order to quiet things down.

          Originally posted by whysimon
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            #6
            I think 2.5 would be a bit small for the s54... afaik the rough calculation is 2.2 cfm/HP and tube flows 115 cfm/in2 so 333hp requires 732 cfm

            2.5in tube gets you 564 cfm
            3in tube gets you 812 cfm
            3.5in tube gets you 1106 cfm
            '89 325i OBD2 S52 BUILD THREAD
            Shadetree30

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              #7
              Dual 2.25" is the smallest you want to go. I ran dual 2.5" with 2 mufflers and headers, and it wasn't THAT loud.

              I ran a FloPro center muffler and anActive Autowerke Gen 3 rear muffler from an E36 M3. Castro Motorsport runs the same middle muffler with a Borls ProXS out back and it sounds greatas well, is a bit quieter and still performs great.

              My old M3:
              This is "Castro Motorsport S54 E30 M3" by Chris Bialy on Vimeo, the home for high quality videos and the people who love them.


              If going with a single system, the merge is super important for low-end and midrange torque. A good tuner can tune out some of the torque loss - heavily dependent upon the Vanos mapping. Single 3" or 3.5" on any car is loud unless you run 2 pretty big and typically more restrictive mufflers. I have an s52 in my Ti with 3" and have a Vibrant Ultra Quiet resonator, another 14" Vibrant resonator and a Borla ProXS out back. It's pretty quiet at idle and at lower rpm, but definitely has the loud sound I want above 4 rpms and at WOT.
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                #8
                Do keep in mind that most non-race exhausts for the E46 M3 are dual 2.5". So, yes, if peak hp is your goal, a 3.5" exhaust is going to probably give the best results. But if you want drivability and reasonable noise, dual 2.5" is more than fine.
                2006 GMC Sierra 2500HD 4WD LBZ/Allison
                2002 BMW M3 Alpinweiß/Black
                1999 323i GTS2 Alpinweiß
                1995 M3 Dakargelb/Black
                - S50B32/S6S420G/3.91
                1990 325is Brilliantrot/Tan
                1989 M3 Alpinweiß/Black

                Hers: 1996 Porsche 911 Turbo Black/Black
                Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

                sigpic

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                  #9
                  dual 2.5" is HUGE.

                  just taking sq/in to CFM isn't accurate, because the surface area of a larger single pipe is less than 2 smaller pipes, which means it flows effectively better even with the same open area.

                  A single 2.5" actually flows about the same as dual 2", because although it has a little less open area (~1sq in), the surface area of the pipe is actually less, which means less friction.

                  Also, you can't just add diameters to get open area. For example, two 1 1/4" pipes are not equal to a single 2.5" in area. it's almost half! (not saying anyone is doing this, it's just pointing out that the difference between 2" to 2.5" is a LOT more than it appears).

                  dual 2.5" has 9.8 sq inches of open area.. that's way more than a single 3" (7sq in) and even more than a single 3.5" (9.6"). It will flow less than a 3.5" though because it has more surface area, it will also weigh more and cost more to build.

                  dual 2.25" is more than plenty (it's still 8 sq inches!).. I'd still go with a single pipe personally, probably 3".
                  Build thread

                  Bimmerlabs

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                    #10
                    You need less size than you think. However If you want to use a small system it needs to be well built with less bends, better merges, high flow cats, high flowing muffler design etc... Otherwise it's not the pipe that will cause a hp loss but the other stuff
                    Last edited by digger; 08-20-2015, 04:51 PM.
                    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

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                      #11
                      I'd do something just like OEM e46M3 is, except lighter. E46 exhaust is a very well engineered system. A lot of guys can suggest do this do that and assume this and assume that but all the hours and testing have been done.

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                        #12
                        I used a 3" single exhaust on my euro S50 and I'm really pleased. Virtually no drone and not super loud until you get on it. Louder than any oem setup but it passes the girlfriend test. Like others say, the torque seems to be dependent on the placement and design of the merge/Y pipe.

                        After a lot of thought I went with a Borla Pro XS in the middle section and a magnaflow in the rear. The borla pro xs fits great next to the driveshaft and from some independent testing I've seen, reviews etc, it seems to pretty pretty darn quiet for a straight through design. Cheap too.

                        If I had to do it over I'd probably still use the Borla but use a Vibrant Streetpower Muffler for the fancy tips. I've read that the vibrants aren't to loud so I don't think it would affect it much. If you wanted it even quieter you could use a turbo style muffler. However, I chose not to do that because the cfm numbers were all pretty lousy on those.

                        I also used some mandrel bends from summitracing ((2) 180 degree bends and a 4' straight section) <$400 for the parts plus your cut and welding.
                        Euro S50 Daily Driver: http://www.r3vlimited.com/board/showthread.php?t=279195

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                          #13
                          Originally posted by Luke_M View Post
                          I used a 3" single exhaust on my euro S50 and I'm really pleased. Virtually no drone and not super loud until you get on it. Louder than any oem setup but it passes the girlfriend test. Like others say, the torque seems to be dependent on the placement and design of the merge/Y pipe.

                          After a lot of thought I went with a Borla Pro XS in the middle section and a magnaflow in the rear. The borla pro xs fits great next to the driveshaft and from some independent testing I've seen, reviews etc, it seems to pretty pretty darn quiet for a straight through design. Cheap too.

                          If I had to do it over I'd probably still use the Borla but use a Vibrant Streetpower Muffler for the fancy tips. I've read that the vibrants aren't to loud so I don't think it would affect it much. If you wanted it even quieter you could use a turbo style muffler. However, I chose not to do that because the cfm numbers were all pretty lousy on those.

                          I also used some mandrel bends from summitracing ((2) 180 degree bends and a 4' straight section) <$400 for the parts plus your cut and welding.
                          hows the ground clearance with borla proxs there? are you lowered?
                          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                          Comment


                            #14
                            Originally posted by nando View Post
                            dual 2.5" is HUGE.

                            just taking sq/in to CFM isn't accurate, because the surface area of a larger single pipe is less than 2 smaller pipes, which means it flows effectively better even with the same open area.

                            A single 2.5" actually flows about the same as dual 2", because although it has a little less open area (~1sq in), the surface area of the pipe is actually less, which means less friction.

                            Also, you can't just add diameters to get open area. For example, two 1 1/4" pipes are not equal to a single 2.5" in area. it's almost half! (not saying anyone is doing this, it's just pointing out that the difference between 2" to 2.5" is a LOT more than it appears).

                            dual 2.5" has 9.8 sq inches of open area.. that's way more than a single 3" (7sq in) and even more than a single 3.5" (9.6"). It will flow less than a 3.5" though because it has more surface area, it will also weigh more and cost more to build.

                            dual 2.25" is more than plenty (it's still 8 sq inches!).. I'd still go with a single pipe personally, probably 3".
                            Yes, but dual 2.5" is proven to work better on virtually any configuration versus any single exhaust, unless you're talking hp made between 7-8k. Almost every after market e46 m3 exhaust is dual 2.5" for a reason.

                            Dual 2.5" without any form of X/H-pipe works great, keeps inline with Vanos mapping in the DME, sounds great, and doesn't rob you of the S54's amazing torque band like most single systems without custom tuning.
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                              #15
                              Originally posted by digger View Post
                              hows the ground clearance with borla proxs there? are you lowered?
                              It's a fairly short height muffler, one of the lowest profile mufflers out there.
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