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  • How best to complete this exhaust

    Howdy. Been a minute.

    I'm wanting to swap the euro spec exhaust from my Evo II with a USA one at least temporarily. It's time to re-up my tags and The EU one won't pass the sniff test in my state but based on previous experience the USA one will. Last time I did the tags we swapped a USA one and it passed easily but it is back to having the EU exhaust on now.

    Previously I had a shop do the work for me but this time I decided to do it myself. I have the stock exhaust off and I have the majority of a stock USA E30 M3 exhaust here but it is missing the back section / muffler.

    So my question is how best to complete the exhaust. Should I:

    1. Source a brand new USA spec exhaust or at least a used complete exhaust?
    2. Have the partial USA spec exhaust that I have completed somehow (with what parts and at what sort of shop?).
    3. Other idea?

    Interestingly the two exhausts look visually almost identical but I guess the interior catalytic converter components would be different? I was under the impression that the EVO exhaust had fewer or no cats at all?

    Also: Since the Evo II exhaust / muffler is super rare does it make any sense to refresh / re-coat it while it is out or does that ruin the originality of it?

    ALSO: what do the clamps do right before the muffler box?

    ALSO it looks like the USA exhaust was cut, so I'm guessing it would need to be welded to the remaining pipe / muffler? Or is that what those clamps do?

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  • #2
    Both are stock (Euro and US are identical) catalytic convertors one obviously is no longer converting (perhaps because the ceramic substrate has been knocked out of it?).
    Both no longer have the alumised heat shielding around them as shown in the pic below on the right.

    Evo2 had no cats but an intermediate silencer pictured on the left in black. This part is identical to and carried-over from the non-cat euro (200hp) M3 to the Evo2.
    Only special exhaust part i.e. Evo2-specific is the exhaust manifold as it is a two part design.
    Back box is shared with the 195/200hp M3 (perhaps it has polished end tips like the cecotto/ravaglia en Evo3, unsure about that but your picture indicates as such).


    Replied below your questions


    Originally posted by monovich View Post
    So my question is how best to complete the exhaust. Should I:

    1. Source a brand new USA spec exhaust or at least a used complete exhaust?
    2. Have the partial USA spec exhaust that I have completed somehow (with what parts and at what sort of shop?).
    3. Other idea?
    Get a supersprint center section without cat convertor and connect a stock back box to that.

    Interestingly the two exhausts look visually almost identical but I guess the interior catalytic converter components would be different? I was under the impression that the EVO exhaust had fewer or no cats at all?

    Also: Since the Evo II exhaust / muffler is super rare does it make any sense to refresh / re-coat it while it is out or does that ruin the originality of it?

    No Evo2 exhaust on your pictures so don't bother.

    ALSO: what do the clamps do right before the muffler box?

    Connect back box to cat convertor

    ALSO it looks like the USA exhaust was cut, so I'm guessing it would need to be welded to the remaining pipe / muffler? Or is that what those clamps do?

    indeed

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    • #3
      Hi Monovich,
      The clamps let you attach the cat to the muffler without welding. That makes it easier to change things. The clamps are originally used on a US 528i which has the same diameter. They replace the swaged clamps that are original on US M3's. And they are stainless so use some antiseize compound when you assemble things. If the cat pipes have been cut short, the clamps might not work well.
      Larry

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      • #4
        Thanks for the info y'all.

        So there *might* be a catalytic converter in both midpipes, but on the one on the right from the UK the converter might be crumbled / gone / not working if it isn't passing smog with it. The one on the left from the USA car may or may not be there and still work, but I'll only know if I disconnect the clamps to the muffler on the UK one, move to the USA one, and re-test the car.

        Otherwise the solution might just be:

        1. Buy a catalytic midpipe: https://www.bimmerworld.com/Exhaust/...r-Section.html
        2. Unbolt the stock muffler box and bolt it to the new midpipe.

        Apologies on the newb questions. I'm just doing more wrenching on my car these days.

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        • #5
          What I am surprised at is Colorado makes a 30 years old car pass a sniff test. If the fed's give a pass to emissions and safety at 20 years maybe Colorado should as well.
          Who knows where I'll be, changes from day to Continent.

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          • #6
            Originally posted by M-technik-3 View Post
            What I am surprised at is Colorado makes a 30 years old car pass a sniff test. If the fed's give a pass to emissions and safety at 20 years maybe Colorado should as well.
            1976 checking in... Let me tell you about it. All the 90's and 00 cars that need o2 and MAF sensors, and yet they sweat my '76. (They freaked out when they opened my hood... "Where's the carb?!" Full s14 sitting there...)
            Dave.
            76 M2

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            • #7
              There are certain parts that don't make sense replacing with OEM and your exhaust is one of them. I would purchase the VSR mid section, connect it to your OEM muffler and call it a day. Keep your original EVO center section for posterity (and in case you ever sell the car you'll have the original part). Call Mario at VSR and confirm the pipe diameter of his center section is the same as your muffler.

              The VSR center section is going to weigh less and flow better than your OEM part. A better solution all around.

              Doubtful anyone is going to crawl under your car and call you out for not having an OEM center section.
              1990 M3

              Usually it's best not to know how much money you have into your M3

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              • #8
                Managed to get the original center section out, clean up the replacement one that I have, clean up the connection point where the US spec one had been cut at the weld, and bolted up to the back box. It is all back on the car now so that feels great.

                Unfortunately I'm having a no start issue now.

                Case history:

                1. It is never really that happy starting after not driving it for a few months. Usually takes extra cranking and runs a little rough until it warms up. But once warm and up to speed it runs like a top and starts easily again unless I let it sit again. This time it sat for six months unfortunately...

                2. Nothing has changed since I last drove it except for sitting six months and the new mid section but now it won't start. It cranks and cranks but nothing catches and it just doesn't come to life.

                My only thinking is that the fuel is collectively pretty old by now. Maybe a year old total. I didn't expect to have it sitting this long so I didn't prep it for sitting.

                I'd love some thoughts on things to look for. I'm only a 5/10 mechanic. I get intimidated easily. I could work at this or take it back by the shop and have them sort it all out but I do like the idea of getting to know the car better. Any help or links to relevant threads / info would be welcome. I've never attempted to drain a tank before but it seems like fresh gas would be good to start with. I'll do some searching and youtubing...

                edit: I'm pretty sure I can hear the fuel pump so I'm pretty sure that is working.

                -SF

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                • #9
                  Could be any number of reasons:

                  1) Clogged injectors
                  2) No power to the injectors
                  3) Low voltage to the injectors
                  4) ECU does not "see" the flywheel turning because the flywheel sensors (2) may not be communicating with the ECU (or they have gone bad)
                  5) No fuel to the injectors
                  6) No spark
                  7) Fuel pump relay
                  8) Main relay
                  9) Battery not putting out enough voltage

                  These are just the ones I could think of off the top of my head. Check the simple stuff first (i.e. 2, 3, 5, 9).
                  1990 M3

                  Usually it's best not to know how much money you have into your M3

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                  • #10
                    Stuck injectors....
                    Tap them (all four of them ) with the handle of a large screw driver whilst someone else is starting the engine (put it in neutral beforehand!)

                    If you are on your own you can start the engine by turning the key to ignition on and then start cranking by connecting terminal 11 and 14 inside the diagnostics socket in the engine bay. That way you have one hand free to do the tapping.

                    PS. Not sure (as no reaction) if you got the info that the mid section that the car arrived with from the UK is not the original Evo2 mid section.

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