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Yoshifab plenum: Noisy?

Tfrasca

Active member
Joined
Apr 20, 2015
Location
Ben Lomond, CA
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.
 
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.
 
No such noise on the 16v :e-shrug:

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.
 
May be add a weight to in? Done on exhausts all the time.

74371d1501529064-exhaust-resonance-vibration-wieghts-exhaustdampner2_zps148bcf92.jpg
 
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.
 
May be add a weight to in? Done on exhausts all the time.

74371d1501529064-exhaust-resonance-vibration-wieghts-exhaustdampner2_zps148bcf92.jpg

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.
 
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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