Straight exhausts on R53

Discussion in 'Car Builds, Projects, Idea's Experiments' started by drPhilGandini, May 19, 2009.

  1. drPhilGandini

    drPhilGandini MINI of the Month May 2009

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    #1 drPhilGandini, May 19, 2009
    Last edited: May 21, 2009
    I thought I'd start a thread on MotorAll about this, even though the thread on NAM is not so bad. Perhaps this will become a Library thread if we can pull together some common data.

    The photo below shows my final system, which includes a large volume perforated and packed muffler and a packed terminated resonator, using the Helmholtz principle, to attenuate the annoying resonance/drone around 3200 rpm. This system is 2.5" starting with a custom CMC header (4-2-1, ceramic coated inside and out), 200cell race cat, Hushpower II resonator and the muffler you see in the photo.

    [​IMG]

    In order to install a straight exhaust in a R53 you must relocate the battery and remove the battery box. There's another thread on that: http://www.motoringalliance.com/forums/experiments-prototypes-ideas/740-battery-delete.html
     
  2. Mike

    Mike New Member

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    Huh. What does the smaller device to the right do?
     
  3. Jabbles

    Jabbles New Member

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    I vote for an audio sample
     
  4. FUEGO

    FUEGO Club Coordinator

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    Is this the thread you were referring to?
     
  5. Nathan

    Nathan Founder

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    You do know for every link to "that other site" from here you need to place 2 on there back to here.... :ihih:
     
  6. PGT

    PGT Wheel Whore

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    sounds like a fair deal to me :lol:
     
  7. GrAy RaVeN

    GrAy RaVeN New Member

    Now I know where I have seen that before.....

    That's a shark exhaust and a sucker fish ?

    [​IMG]

    [​IMG]
     
  8. drPhilGandini

    drPhilGandini MINI of the Month May 2009

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    :idea:
    That's a Helmholtz resonator, Dr Mike. An audio concept, used in taming resonance frequencies in speakers, and recording studios/listening rooms, for example. It's a tuned closed-end column of air, designed to absorb acoustic energy of a particular frequency. In this case, the exhaust system "drones" at a particular rpm, and the Helmholtz resonator is tuned to the associated frequency and absorbs the energy at that frequency.
    So the exhaust sounds normal (loud, growly, etc) at all rpm/frequencies and rather than being louder at the drone, it's about normal thanks to the Helmholtz.
    :idea:
    It actually works. I've seen then on OEM Honda S2000 exhausts, on aftermarket Z350 exhausts and there's a big thread about them on some Mustang forums. The cross-pipe on Corvette exhausts and other v-8 systems acts in a similar way to attenuate certain frequencies.
     
  9. drPhilGandini

    drPhilGandini MINI of the Month May 2009

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    As for the thread referred to on the other site, there's another one there also. There's a lot of good information in those threads, for sure. I just thought I'd put one here, to see if we get some new ideas.
    When I get some time and soon, I'll add the battery box delete pre-amble and tell the whole story in one place. Then maybe we can make it a Library thread. I get the idea that Library threads are more meta-analysis and composites of all the ideas on a particular topic.
     
  10. Mike

    Mike New Member

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    I believe you that it works (OEM intakes typically use Helmholtz resonators too).

    It appears that they terminated the resonator pipe with a capped-off glass-pack, perhaps to knock down the Q of the resonator.
     
  11. Ryephile

    Ryephile New Member

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    I have two versions of the straight through I did on MM2, one being a scavenger box Flowmaster during the supercharged setup and the latter being a shot while fabbing the exhaust for the turbo project. I cut out the battery box and relocated a small battery beneath the drivers' seat for tighter polar inertia. Yes, I used the factory aluminum aero pan as a heat-shield, it worked fantastic!

    [​IMG]

    [​IMG]
     
  12. PGT

    PGT Wheel Whore

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    yes....I was just about to mention the intake application :D
     
  13. minispeedrcr

    minispeedrcr New Member

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    #13 minispeedrcr, May 20, 2009
    Last edited: May 20, 2009
    Straight pipe on Race Car

    So I have a Mini I race with USTCC and at the first race I had a muffler failure.
    http://www.flickr.com/photos/[email protected]/3489141656/
    [​IMG]
    Any recommendation on what muffler would be a good replacement since you guys seem to have a little experience at this. Main issue is the sound limit is a 103 decibels at the tracks here in Northern California. I went out with just a straight 3" pipe and the sound was over 107 db at thunderhill. I'm running a Webb custom header in 3" that goes into a reonator just past the header then straight out the back. the current setup does have an annoying reonance at about 5000 rpm.

    Vince Parker
    USTCC #96 Mini
     
  14. Mike

    Mike New Member

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    Hi Vince, your posted image doesn't seem to work.

    Any, I defer to the other guys on exhausts. I just have a standard-issue Magnaflow (which I love) but I don't think that's what you are looking for.
     
  15. minispeedrcr

    minispeedrcr New Member

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    Sorry I can't seem to make the picture thing work. suggestions?
     
  16. Nathan

    Nathan Founder

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    [​IMG]

    Here ya go...

    Instead of copying the URL right click on the image and select copy image location or something to that effect depending on the browser.
     
  17. Ryephile

    Ryephile New Member

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    --->minispeedrcr: Did you buy Randy's MINI? I was wondering where that ended up! Regarding your concern, it looks like the metal simply disintegrated from too much heat. I would recommend going with at least some 304-grade stainless tubing [usually 18 awg is all that's needed] from the header rearward and then use whatever muffler tickles your fancy [3" in/out perf-core like a Magnaflow muffler would change the peak torque slightly]. Is the battery box cut out, or does the pipe run underneath it? This would significantly impact the nature of a recommendation.
     
  18. drPhilGandini

    drPhilGandini MINI of the Month May 2009

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    Vince, 103db is not so loud. I'd guess mine is as low as that. With your system a big can might work. I have a custom can made from CMC (Juston Poole) but it's basically a large volume packed muffler with perforated straight through pipe. The Helmholtz resonator is purely to attenuate the drone, it does nothing for the performance or sound at other frequencies. It does add weight, though.
    I do have one warning based on my experience--you must stay away from baffled or metal only mufflers. They are very loud, very "bright" and don't work with the R53. As Jan from RMW told me many times, the SC engine is incredibly loud, and he's right. Much louder than a turbo motor, or even a NA motor.
    Also remember that the header/cat impacts the overall exhaust noise. My Megan catless header was *much* louder than my CMC header with 200-cell cat.

    I just saw Ryephile's post. If that's Randy's red car, then I'm glad to see he made that 3" header--he was always talking about it to me, and I actually held off buying one for a year or so hoping he'd get around to it. But, lo, I fear that one on your car is the only one ever made.
     
  19. minispeedrcr

    minispeedrcr New Member

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    yes I bought randy webbs mule in December off eBay. Gotta love eBay! Battery is relocated, straight 3" pipe that goes through the rear diffuser and under carriage panel. Anbody tried the Supertrapp sound tunable muffler?
     
  20. Ryephile

    Ryephile New Member

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    To deviate for a second and comment on drPhilGandini's statement; my Flowmaster scavenger box [pic at top of page] made 5wHP @ over a standard Milltek cat-back [and lost power nowhere], so they do work over a simple perf-core muffler provided they're well designed. That said, it was louder than having a straight pipe, so it's definitely not recommended to minispeedrcr for a loudness fix!

    Most likely a good solution for minispeedrcr will be to cut out the battery box, make a flat boot floor, and install a big volume perf-core muffler like a Magnaflow.
     

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