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Old 05-19-2009, 05:55 PM   #1
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Straight exhausts on R53

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.

Click the image to open in full size.

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: Battery Delete
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Old 05-19-2009, 06:33 PM   #2
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Huh. What does the smaller device to the right do?
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Old 05-19-2009, 06:44 PM   #3
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I vote for an audio sample
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Old 05-19-2009, 06:50 PM   #4
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Is this the thread you were referring to?
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Old 05-19-2009, 06:59 PM   #5
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Quote:
Originally Posted by FUEGO View Post
Is this the thread you were referring to?
You do know for every link to "that other site" from here you need to place 2 on there back to here....
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Old 05-19-2009, 07:50 PM   #6
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sounds like a fair deal to me
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Old 05-19-2009, 09:29 PM   #7
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Now I know where I have seen that before.....

That's a shark exhaust and a sucker fish ?

Click the image to open in full size.

Click the image to open in full size.
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Old 05-20-2009, 12:21 AM   #8
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Quote:
Originally Posted by drmike@txwerks View Post
Huh. What does the smaller device to the right do?

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.

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.
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Old 05-20-2009, 12:28 AM   #9
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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.
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Old 05-20-2009, 12:56 AM   #10
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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.
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