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    Stroker M20 exhaust

    I want to fix up my exhaust. I’m looking to go to a single pipe probably 3” because stuff is more readily available in 3” vs 2.75” and backpressure with 3” things like catalytic converter, resonators and muffler would only seem to be less though maybe not proportionally since it’s the guts of it that governs flow and often the guts are the same/similar


    CONFIGURATION



    MERGE

    Plan on ridding the X pipe


    And adding one of these venturi collectors from burns, not sure what venturi size would be best and would make it so that the position can be varied without too much difficulty to test a couple different lengths as it seem to have a big impact on torque and power over a pretty large band of rpm



    RESONATOR

    A hate too much drone and excessive rasp
    I’m thinking vibrant ultra-quiet resonator. Anyone used this? Anything better around? ground clearance a probelm?



    CATS

    Due to legality I must run
    Will use high flow 100cell metal cat with nice gradual expansion and contraction example below



    MUFFLER

    I like twin exit aesthetics so single in dual out it needs to be what I have seen. Anyone know what brands would fit behind mtech2 rear skirt

    Borla

    http://www.summitracing.com/dom/part...0670/overview/
    http://www.summitracing.com/dom/part...0349/overview/

    dynomax

    http://www.summitracing.com/parts/wlk-17273/overview/
    http://www.summitracing.com/parts/wlk-17519/overview/
    http://www.dynomax.com/mufflers/dyno...ed-offset.html

    Anyone got pics of their exhaust from underneath?
    Last edited by digger; 08-23-2019, 01:56 AM.
    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


    #2
    Nice thread. I think the Vibrant is the best resonator out there, as far as I have read. It's been used quite a bit.
    REMEMBER: Be safe and have fun is Rule Number 1.

    The Epic Unbuild of Clint Eastwood

    Comment


      #3
      Originally posted by MaxBell View Post
      Nice thread. I think the Vibrant is the best resonator out there, as far as I have read. It's been used quite a bit.
      thats what i found with my quick search, thanks.

      anyone got a m20 with borlas pro XS? sound clips?
      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


        #4
        part of the reason i want to redo the exhaust is that i did some changes a couple years ago that hurt power alot. mostly moving the X-pipe too close to the engine.



        100km/h is 3400rpm. so at about 3600rpm there is a 15kw loss which is 14% loss of midrange.

        The two most powerful naturally aspirated M20 engines publically known both use single exhaust so it works. knowing this pipemax says 32" is the correct location for the Y-pipe and Burns X-design says 30". So both are in good agreement so that's decided.

        The current exhaust has been butchered and modified alot and there are so many step changes. i have 2" secondaries to an X-pipe then 2x 1-7/8" into 2 x 2-1/4" then im sure there are a few places where it looks 2 x 2.5" to join the resonator and muffler which doesn't help droning.
        Last edited by digger; 08-23-2019, 01:58 AM.
        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


          #5
          Interesting, so if you combine to 1 pipe too early or too late, you lose power? How significant?
          REMEMBER: Be safe and have fun is Rule Number 1.

          The Epic Unbuild of Clint Eastwood

          Comment


            #6
            Originally posted by MaxBell View Post
            Interesting, so if you combine to 1 pipe too early or too late, you lose power? How significant?
            yes, in my case i had the x-pipe too close it seems it was about 400mm when might be better to have used 800mm or 1600mm which are also harmonic lengths that provide more torque theoretically but when you have cats, resonators and mufflers this can throw it all out the window. if you look where OEM puts H-pipe on S54 it has halfway down, now it is a different engine but new m20 engine will be similar in allot of ways as far as engine size, power and torque numbers
            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


              #7
              anyone got any thoughts on using a muffler instead of resonator?

              i'm thinking of ground clearance. the vibrant ultra quiet is 4.5" and i can get a borla pro xs in 4" height so thats a decent amount difference.

              would a muffler be a better resonator than a bottle style resonator?

              i would then run a dynomax muffler in the muffler position so have two mufflers rather than a resonator and muffler
              Last edited by digger; 05-10-2014, 01:22 AM.
              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


                #8
                Im starting to think the sizes might not be big enough to support the power output either. Remembering rough tables you can use as a guide, 3" single is good for about 750cfm and supports about 320-330hp, while 2" is about 320cfm and somewhere around 150hp. Used in twins, it's less than 300hp. I know it's only a guide and the figures are probably a little underestimated rather than being dead on, but you might have to step up to 3 1/4" and 2 1/4" secondaries to support the power this thing could potentially put out. Im only using other rough figures as a guide, but what are you expecting, have to be somewhere in the range of 330hp (or more)?

                As far as construction goes and components, I reckon it is going to be a case of how quiet you really want this thing to be and potentially having to tune out some of the drone or frequencies you hate. You can get some super high flow mufflers like those spintech race series or dynomax ultraflow mufflers which flow absolute shit loads and are pretty compact (especially in the case of the spintech). Used a few on V8's recently but they probably aren't going to quieten it down enough for you though. Along with some of the flow masters, they would be pushing mid 90's to 100db I reckon.

                Not running a resonator is really just going to be about your personal taste I think and you'll probably just have to try it and see. Not so much from a loudness stand point, but if there is too much crackle or bark that you can't stand. If there is, you'll probably have to add in a resonator which will take out some of the higher frequencies and leave you with the lower burble.

                Normally I'd be inclined to build one without a resonator and see what it sounds like, but in this case with a single system and the fact you hate any rasp and crackle, I don't think you are going to get around this and will have to run one. I would probably make a suggestion that if you are going to only run a single muffler in the system, id be stepping up to the next full size in diameter into the muffler which will help quieten it down more. If you are running a 3" system, id look at maybe stepping up to a 4" entry muffler, something as long as you can physically fit between the diff and the valance, talking in the realm of 18-20" long. Should give you the best change at reducing volume as much as possible, especially if you run something that is advertised as high flow/horsepower, so bigger entry in and longer is going to help keep it quiet.
                Just a little project im working on
                - http://www.lse30.com -

                Comment


                  #9
                  Originally posted by Madhatter View Post
                  Im starting to think the sizes might not be big enough to support the power output either. Remembering rough tables you can use as a guide, 3" single is good for about 750cfm and supports about 320-330hp, while 2" is about 320cfm and somewhere around 150hp. Used in twins, it's less than 300hp. I know it's only a guide and the figures are probably a little underestimated rather than being dead on, but you might have to step up to 3 1/4" and 2 1/4" secondaries to support the power this thing could potentially put out. Im only using other rough figures as a guide, but what are you expecting, have to be somewhere in the range of 330hp (or more)?

                  As far as construction goes and components, I reckon it is going to be a case of how quiet you really want this thing to be and potentially having to tune out some of the drone or frequencies you hate. You can get some super high flow mufflers like those spintech race series or dynomax ultraflow mufflers which flow absolute shit loads and are pretty compact (especially in the case of the spintech). Used a few on V8's recently but they probably aren't going to quieten it down enough for you though. Along with some of the flow masters, they would be pushing mid 90's to 100db I reckon.

                  Not running a resonator is really just going to be about your personal taste I think and you'll probably just have to try it and see. Not so much from a loudness stand point, but if there is too much crackle or bark that you can't stand. If there is, you'll probably have to add in a resonator which will take out some of the higher frequencies and leave you with the lower burble.

                  Normally I'd be inclined to build one without a resonator and see what it sounds like, but in this case with a single system and the fact you hate any rasp and crackle, I don't think you are going to get around this and will have to run one. I would probably make a suggestion that if you are going to only run a single muffler in the system, id be stepping up to the next full size in diameter into the muffler which will help quieten it down more. If you are running a 3" system, id look at maybe stepping up to a 4" entry muffler, something as long as you can physically fit between the diff and the valance, talking in the realm of 18-20" long. Should give you the best change at reducing volume as much as possible, especially if you run something that is advertised as high flow/horsepower, so bigger entry in and longer is going to help keep it quiet.
                  David Vizard recommends 2.2CFM per hp so 720CFM and graham Bell says a 3" is good for 320bhp. DYnomax VT 2.5" flows 970cfm (according to them) so 3" is probably more. In Vizards book a 3" borla flows the same as the pipe. im sure it wont be costing any meaning amount of hp. i'm not expecting anymore than 320-330bhp with the CR and duration i will use.

                  Rama made 290rwhp through a 2.5" system AFAIK (definitely when he was 260rwhp it was 2.5") and IIRC recently upgraded to a 3" and said not a big difference. Robs 2.8L with 360rwhp uses 3" so should be fine.

                  i wouldnt run a single muffler. id run a another muffler in place of a resonator so have two mufflers
                  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


                    #10
                    Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

                    I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.
                    Lorin


                    Originally posted by slammin.e28
                    The M30 is God's engine.

                    Comment


                      #11
                      Originally posted by LJ851 View Post
                      Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

                      I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.
                      yeah thats why i asked about a muffler instead of a bottle style (hot dog) resonator the extra volume is surely better. im running two at the moment (either 2.25" or 2.5" not sure) and there is hardly any volume in them so i wonder how effective they actually are. my muffler is huge though 22" long 12" wide at the body

                      Originally posted by LJ851 View Post
                      I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.
                      i havent found specifics for the borla pro xs but since itwould go in place of a glasspack an XR1 would also work subject to being compact.

                      the best clearance would be with one of these

                      http://www.borla.com/products/xr1_se...rt__40536.html

                      but added expense of two oval transition pieces which might not be justifiable given at the end of the day my cat is lowest point at the moment though the new cats will be a little more compact at 4" as it doesnt have the heat shield. im not sure how low a 4" body cat would hang when hugging the body
                      Last edited by digger; 05-10-2014, 05:13 PM.
                      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


                        #12
                        Originally posted by LJ851 View Post
                        Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

                        The decibel output is not reduced (by much...), but the frequency is changed by the resonator. I don't have the formula/s on hand, but you can calculate everything out to produce the tone you desire. The general purpose is to target a certain RPM band; for instance a highway cursing scenario that has terrible drone can be fixed by either adding resonator pipes, or reconfiguring the exhaust. Theory in practice seen here....

                        http://www.modified.com/tech/modp-11...ng-test-pipes/

                        IIRC the s2000 had resonator pipes stock near the rear muffler, but I could be wrong. Speaking of s2000's, I came across this awhile back and think you might find it interesting. Not practical on your time frame, but food for thought....

                        http://www.s2ki.com/s2000/topic/9919...ipe-group-buy/


                        Also, the venturi from what I have read is either purely snake's oil, or has a very minimal effect. Although, the link above makes me think twice about that. It would be a ton of arithmetic to calculate the scenario, but it is definitely is worth looking into. Did you speak directly to burns about your exhaust plans, and if so, what did they have to say? The fact that they produce them to begin with does mean that there is merit to the idea, but I came across this insightful bit...

                        Best look at exhaust systems that no one is trying to market to you if you are considering performance. A place where they are spending hundreds of millions of dollars trying to squeeze horsepower out of an internal combustion engine, and where they aren't trying to sell you some billet trinket, is probably a good place to start to find some answers to these exhaust questions.
                        As you have stated and already figured out (length), the merge on single merge collector's secondary is very, very important. A (m20 scenario) 2-1-2-1 set up would not be as crucial on the last merge, but rather the secondaries themselves are the most crucial, even more than the primary length/merge. NASCAR has heaps of info on header design, but you have a really nice set to begin with.

                        Also, my understanding of everything after the merge and "open exhaust" scenario leads in the direction of as long as the units can flow the peak CFM produced you can do what you please. I don't have any experience with the mufflers you are planning on using, but I made a header back exhaust that sounds great with minimal drone and rasp. The drone and rasp that did occur was due to the thin headers I was using. If you were local to me I would do your exhaust for free since you have given myself, and the whole forum a vast amount of knowledge! Please have it TIG'ed, back purged, and NO cheater bends! Good luck with your exhaust and I hope some of this was helpful :up:
                        sigpic

                        A man chooses, a slave obeys... Would you kindly?

                        Comment


                          #13
                          Originally posted by pantelones View Post
                          The decibel output is not reduced (by much...), but the frequency is changed by the resonator. I don't have the formula/s on hand, but you can calculate everything out to produce the tone you desire. The general purpose is to target a certain RPM band; for instance a highway cursing scenario that has terrible drone can be fixed by either adding resonator pipes, or reconfiguring the exhaust. Theory in practice seen here....

                          http://www.modified.com/tech/modp-11...ng-test-pipes/

                          IIRC the s2000 had resonator pipes stock near the rear muffler, but I could be wrong. Speaking of s2000's, I came across this awhile back and think you might find it interesting. Not practical on your time frame, but food for thought....

                          http://www.s2ki.com/s2000/topic/9919...ipe-group-buy/


                          Also, the venturi from what I have read is either purely snake's oil, or has a very minimal effect. Although, the link above makes me think twice about that. It would be a ton of arithmetic to calculate the scenario, but it is definitely is worth looking into. Did you speak directly to burns about your exhaust plans, and if so, what did they have to say? The fact that they produce them to begin with does mean that there is merit to the idea, but I came across this insightful bit...

                          As you have stated and already figured out (length), the merge on single merge collector's secondary is very, very important. A (m20 scenario) 2-1-2-1 set up would not be as crucial on the last merge, but rather the secondaries themselves are the most crucial, even more than the primary length/merge. NASCAR has heaps of info on header design, but you have a really nice set to begin with.

                          Also, my understanding of everything after the merge and "open exhaust" scenario leads in the direction of as long as the units can flow the peak CFM produced you can do what you please. I don't have any experience with the mufflers you are planning on using, but I made a header back exhaust that sounds great with minimal drone and rasp. The drone and rasp that did occur was due to the thin headers I was using. If you were local to me I would do your exhaust for free since you have given myself, and the whole forum a vast amount of knowledge! Please have it TIG'ed, back purged, and NO cheater bends! Good luck with your exhaust and I hope some of this was helpful :up:
                          from my understanding the gradual change of a venturi produces an affect over a wider rpm band than an abrupt area change and it helps at the bottom end if nothing else. apparently allows you run shorter primaries which canproduce more topend. my header primaries are a little short by 2" so might work to my favour....idk

                          they look pretty cool at worst, supposed to arrive on monday

                          i emailed roman but did not speak to him, the time difference at this time of year is prohibitive.

                          i will ask for non slip joints to be TIG'd im not going to go to an elcheapo exhaust place
                          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 digger View Post
                            they look pretty cool at worst, supposed to arrive on monday
                            Ha, yeah I agree with that. Sometimes I forget you are on the other side of the planet Calling burns would be kind of difficult haha

                            Are you going to be using a flex pipe? I put mine right after the merge, but at that point in time I was just making the exhaust and not engineering it so to speak. Also, are you separating the exhaust? I did mine in three pieces, well six total if you include the headers. The Accuseal clamps work great if you don't want to run v-bands. I would also recommend TIG'ing everything, even the slip fits; the penetration control is just so much better and it just looks cleaner. The flex pipe is a slip fit on my merge collector. This was my first TIG protect too, and now I have much better bead uniformity haha

                            IMG_4150 by Los Pantelones!, on Flickr

                            I also did not back purge mine, and it turned out okay. For 304 stainless it's a must, and would not look this clean on the inside.

                            IMG_4149 by Los Pantelones!, on Flickr
                            sigpic

                            A man chooses, a slave obeys... Would you kindly?

                            Comment


                              #15
                              Originally posted by pantelones View Post
                              Ha, yeah I agree with that. Sometimes I forget you are on the other side of the planet Calling burns would be kind of difficult haha

                              Are you going to be using a flex pipe? I put mine right after the merge, but at that point in time I was just making the exhaust and not engineering it so to speak. Also, are you separating the exhaust? I did mine in three pieces, well six total if you include the headers. The Accuseal clamps work great if you don't want to run v-bands. I would also recommend TIG'ing everything, even the slip fits; the penetration control is just so much better and it just looks cleaner. The flex pipe is a slip fit on my merge collector. This was my first TIG protect too, and now I have much better bead uniformity haha

                              IMG_4150 by Los Pantelones!, on Flickr

                              I also did not back purge mine, and it turned out okay. For 304 stainless it's a must, and would not look this clean on the inside.

                              IMG_4149 by Los Pantelones!, on Flickr
                              im not currently running a flex pipe seems to work ok like that.

                              i will have segments, there is currently a slip joint and a flange joint. slip joint will remain with clamps.

                              butt welds will be TIG and purged, bends will be mandrel ones
                              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

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