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Old 09-29-2017, 12:14 PM   #1
Tfrasca
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Default Yoshifab plenum: Noisy?

Has anyone else noticed a lot of engine noise coming through their Yoshi plenum? Mine seems to resonate and almost makes the B23 motor sound like a diesel. If I put my hand on the plenum, all that noise stops.

I'm wondering if it's just the thin sheet metal not insulating sound, or if it's some kind of weird resonance in the way I designed the manifold.
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Old 09-29-2017, 01:17 PM   #2
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Thin sheet metal, in addition to free flowing design, which won't restrict noise coming out of the intake.
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Old 09-29-2017, 01:20 PM   #3
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Originally Posted by Benjam83 View Post
Thin sheet metal, in addition to free flowing design, which won't restrict noise coming out of the intake.
Does it bother anyone else enough to do something about it?

I had a panel of sound deadening material on it, but that looked terrible and was only marginally effective. I thought about welding a big sheet of 1/4" aluminum to it to dampen some of the sound. Wondering if anyone has tried anything similar.
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Old 09-29-2017, 01:33 PM   #4
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how about fixing some alu U-profile on the long flat surfaces ?
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Old 09-29-2017, 01:47 PM   #5
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No such noise on the 16v
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Old 09-29-2017, 01:55 PM   #6
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No such noise on the 16v
Interesting. It could be that my velocity stacks are about an inch or so away from the back wall of the plenum. So maybe whatever Helmholtz stuff is going on is causing the noise.

I'll try to get a video of it. It's pretty weird.
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Old 09-29-2017, 02:06 PM   #7
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May be add a weight to in? Done on exhausts all the time.

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Old 09-29-2017, 02:15 PM   #8
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May be add a weight to in? Done on exhausts all the time.

Yeah, that's my thought with adding a sheet of 1/4" to it.
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Old 09-29-2017, 11:09 PM   #9
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If it's resonating (vibrating) you may only need to tweak the housing to get it to stop. Sounds crude, but you may only need to dimple it in a couple places to get it to stop.
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Old 09-30-2017, 08:54 AM   #10
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Quote:
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May be add a weight to in? Done on exhausts all the time.

Exactly. The natural frequency is a function of (among other things) the mass and stiffness. Bending/buckling/reinforcing a thin "flat panel" gives it more section, and will move the harmonic to a higher frequency.
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Old 09-30-2017, 09:44 AM   #11
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Remove most of the exhaust system, you'll no longer hear your intake noise.
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Old 10-03-2017, 08:34 PM   #12
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Earplugs?
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Old 10-03-2017, 08:40 PM   #13
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Plasti dip it? or bed liner it. to dampen the metal... IDk
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Old 10-04-2017, 10:10 PM   #14
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Remove most of the exhaust system, you'll no longer hear your intake noise.
Side exit, no muffler. Zero intake noise issues. Side benefit of putting your infant directly to sleep as soon as you start the car (assuming you have an infant of course)
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