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Thread: The Definitive Exhaust Upgrade Pictorial

  1. #1
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    The Definitive Exhaust Upgrade Pictorial

    Hey guys - I am the king of dreaming-up projects, typically way faster than I can execute them! Continuing with that theme, I've been wanted to free the M30 of the restrictive exhaust noose and liberate that sweet straight six.
    Based on that, I decided to "design" a few options which I present to you below.

    At first I was just going to install the Ireland Engineering cat-back system and be done. But the more I slept on it, I felt I could do better than their system, plus with their set-up you still have to decide to re-use your cat, install a new high flow cat or fabricate a new section if you're not going to run a cat . I would like to mention that IE's set-up has 1.75" O.D pipes, which I feel is on the small side for the M30, plus I did not like their heavy rear muffler, the caveat here is I do like their products and service and I am going to use their ceramic headers as pictured below to replace the stock cast manifolds. As an aside, the header downpipes are 2.0" O.D.

    Side note - The stock exhaust with the cast iron manifolds weighs just over 100-lbs (!)

    Another side note: I will be using stainless flex joints, all stainless pipe, and I will V-Band the exhaust no matter which setup I choose. I have $600 into this little science project..so not too bad.

    Ok so onto the options I came up with, the stock exhaust is shown as a comparo below too, by the way I had lots of fun thinking about this and putting it together:

    Option 1 Side Exit: Twin 2.0" O.D pipes into a single Magnaflow and exit in front of the rear right wheel.
    Pros: Nice and short, fairly easy to fabricate, light, probably will sound cool, looks cool and good power.
    Cons: Heat might damage the paint on the rocker and trim right above that.





    Option 2
    Full length: Twin 2.0" O.D pipes into a single Magnaflow and exit with a 2.5" pipe and twin tips in the stock location
    Pros: Will sound cool, looks cool also and good power.
    Cons: A bit more complicated to fabricate and heavier than the side exit option.





    Option 3
    Ireland Engineering Cat Back system: 1.75" O.D pipes into a resonator and long barrel muffler and exist with 2.0" tips in the stock location
    Pros: Fairly easy to install and fabricate the section where the cat would normally be placed. Decently priced
    Cons: Heaviest of the three options, maybe adds a little less power (smaller 1.75" pipes) than the above two?



    What do y'all think?
    Yasin
    Last edited by slownrusty; 05-11-2019 at 06:28 PM.

  2. #2
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    Wow, what nice set ups. I like #2 with a caveat. I have heard without a center resonator these motors will drone you out. If the center resonator acted as an X pipe, better yet.
    As for #1, where I am, the exhaust has to be clear of the passenger compartment. Therefore only trucks can the run a side exit. Laws might be different in your area. Just a fair warning. It does kind of remind me of the Trans-Am racing series, though.
    You asked my opinion. Next

  3. #3
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    Thanks for the inpu TowJamma - much appreciated.

    My car is registered as an Antique where I live (in Houston, TX) and running a side exit is not a problem here.

  4. #4
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    I wouldn't do side exits for the heat aspect alone, but don't like the idea for other (mainly aesthetic) reasons.

    I dunno - between options 2/3 - probably #2.

  5. #5
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    Here's a thread of a major problem with a flex pipe. Page 5 explains the solution.
    Just a heads up on flex pipes.

    http://www.mye28.com/viewtopic.php?f...9250&start=100

    I installed the IE cat back 2 yrs ago, sound is great and no droning.

    This year built the engine with b34 bottom, b35 Hatrge head, b35 intake, custom JE pistons etc. Going to use

    IE coated headers with x pipe 2 inch dummy cats and custom down pipes. All 2 inch into the 1 3/4 cat back.

    I don't think the restriction to 1 3/4 will cause that much loss in the overall scheme.

    We'll see when it gets tuned with a stand alone. Not going for all out power.

    IE stuff is affordable bolt on quality. IMHO
    Last edited by 1986series6; 05-13-2019 at 07:22 AM.

  6. #6
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    I have your #3 setup without a cat.
    I have a Hartge head, cam, headers etc. Its has a drone at constant speed but sounds awesome (AND LOUD) at foul throttle.
    Just my preference, dont use alot but put the ricers to shame with the inline 6.

    Iain.IMG_3399.jpg

    1985 635 CSi
    Original Owner
    Hartge conversion
    https://www.amazon.ca/photos/share/I...5tKaaMrbsDRAk6

  7. #7
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  8. #8
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    Builder guesses somewhere around 300 ish bhp not rwhp.

    Was going to go with flex but after reading that post and talking to

    the tuner I decided not to.

  9. #9
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    Do any of these exhaust actually increase power on the stock m30? Or might it just move the torque curve up the rpm range (which would lose low end torque)?

  10. #10
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    On a stock M30, I don't think the headers do too much. On an upgraded engine can't hurt.

    "Slownrusty" I would seriously consider an x pipe to help with exhaust scavenging, especially if your going to use an o2 sensor.

    https://www.carid.com/articles/are-x...t-systems.html

  11. #11
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    Quote Originally Posted by 1986series6 View Post
    "Slownrusty" I would seriously consider an x pipe to help with exhaust scavenging, especially if your going to use an o2 sensor.

    https://www.carid.com/articles/are-x...t-systems.html
    Hmmm it says

    “In short, H- and X-pipe exhaust sections benefit V6 and V8 engines because they connect separate pipes coming from the two different exhaust banks found on those engines. Inline engines where all the cylinders are in a row gain nothing, because they have only one exhaust bank.”

  12. #12
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    Even though the m30 is a straight 6, the exhaust setup is 2 banks the same effect as a v6 or v8.

    http://www.realoem.com/bmw/enUS/show...diagId=11_1011

  13. #13
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    Thanks for the suggestions.

    I am going to start the fabrication of the exhaust on my car tomorrow and it will probably continue on into Saturday.

    I'll share some pictures along the way.

  14. #14
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    Made some great progress last night after work, I should be finished up this afternoon. Its falling into place really nicely.


    More pictures to come.

  15. #15
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    That is quick work. Looking good. And, really solid floors.

  16. #16
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    Nice work, did you also create new heat shielding to protect the underbody? They look new, just like the fixation materials.
    Undergoing restauration; my 1982 628CSi: https://www.bimmerforums.com/forum/s...628CSi-rebuild

  17. #17
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    Thanks guys.

    The heat shield that you see in the picture is the original one from 1986, I cleaned it and cleaned it and then polished it, using the stuff I typically use on my aluminum wheels, it came out looking new!

    It is 100% complete now, total fab. time was 9.5 hours. I'm excited to hear the car sounds and runs, still need to button up a few things before I turn the key.

    Here is the last section from the muffler to the tailpipe:

    In progress 3.jpg
    Last edited by slownrusty; 05-19-2019 at 09:03 AM.

  18. #18
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    Next step to ditch the original metric wheels....or should I say you will once you see the cost if you need to by them new
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  19. #19
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    Follow-up, I really like the sound of the exhaust, it that straight six low growl when the toodling around that is not intrusive but barks when you hit the "wow" pedal. I know this as my wife accompanied me on the maiden voyage and she is very sensitive to loud, drone-y exhausts. If I went with the side exit, the story would be certainly different.


    In terms of performance its hard to tell how much additional power I picked up (I should have dyno'd the car before...grr!), but seat of the pants is in the 15-20hp range.


    Here is a quick video, enjoy and tell me what you think!:

    https://www.youtube.com/watch?v=ynI4Y-imtPQ
    Last edited by slownrusty; 05-27-2019 at 10:37 AM.

  20. #20
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    Looks like nice work; you've got a good thing going there. I watched the video and it has a sweet idle. One question though: are the flex pipes really necessary? The stock downpipes are solid to the resonator, and don't seem to suffer for it. Or did you install them because of the fact you're using headers?

  21. #21
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    Larry - Thanks! Glad you liked the video and the rumble. The flex pipes are necessary, they really help to remove the stress on the exhaust studs and also help aligning the exhaust pipes, otherwise the entire exhaust would act as one long cantilever (pinned at the block). Its amazing how much flex and movement there is with the engine and chassis even with new mounts and such. Its precautionary and cheap insruance.

  22. #22
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    Awesome work! What part of Texas you at? I also hit the subscribe button.

    I did a custom setup on mine as well. I will take pictures next time I have it up in the air for reference and to share my results.

    Sent from my Phone using Tapatalk

  23. #23
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    Quote Originally Posted by JSannnn View Post
    Awesome work! What part of Texas you at? I also hit the subscribe button.

    I did a custom setup on mine as well. I will take pictures next time I have it up in the air for reference and to share my results.

    Sent from my Phone using Tapatalk

    Thanks! I am in Houston and please share pictures of your setup.

  24. #24
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    Did you consider Supersprint exhaust system? I looking to upgrade my M635csi.

  25. #25
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    The Supersprint system is nice but very expensive. In my opinion, the quality of their system, is no better than what I fabricated for less $$.

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