Re: Turbo Whistle; where art thou? - Saab NG900 & OG9-3 Bulletin Board - Saabnet.com
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Re: Turbo Whistle; where art thou?
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Posted by Dean (more from Dean) on Fri, 24 May 2002 19:08:44 Share Post by Email
In Reply to: Re: Turbo Whistle; where art thou?, Maarten, Fri, 24 May 2002 16:52:03
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No silencer on your vehicle.

There are two components to the sound.

The sound at the inlet will radiate through the air box if it can, but the inlet will not whine very much. Perhaps some of the impeller discharge noise will propagate back through the impeller but that is less likely I am thinking as the cfms and velocities get up.

Then there is the turbo disharge noise. That probably makes noise. But it goes though the IC and it is probably a good filter. But until the BPV closes, there is a noise path through the BPV return hose. Perhaps such noise can be heard with a dump valve.

But that noise also ends up in the air box.

The filter element may offer some sound dampening, but you always have a filter. The NG900 air boxes have a 15" long snorkle tube, with a large portion impaled to the air box. It is 50mm and this forms an accoustic low pass filter. A helmholtz resonator as well. This is often removed as it has high flow losses. When replace with a 3" pipe or funnel mode, you can hear the turbo. But is is like the bigh trucks... lots of woosh, but as the frequency goes up, the volume drops. Why? BPV closes, flow changes, goes ultrasonic? I don't know.

No sustained jet engine sounds.

posted by 65.68.100...

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