Marty,
Yes! The engine will pull the intake tract through many "different"
frequencies. Its the one @ 2200 rpm that sets up a standing wave in the
intake tract and starts howling that you would want to eliminate! Much like
the whistling FIPK syndrome! My thought was that the intake tract must
"play" with the resonant cavity tuning of the intake manifold, but cant be
obnoxious under the normal RPM range. As a "constrained" factory designer
with a lot of conflicting priorities Id be skeered to put a "Tune" to the
intake tract for anything but noise reduction, knowing that the final cut by
the QA group will be made on sound, not actual performance...Wimps...Any Ide
how long the intake runners on the 4.7 are? I need to get under the hood of
one soon...
Bruce
----- Original Message -----
From: Marty Galyean <mgalyean@acm.org>
To: <dakota-truck@buffnet.net>
Sent: Tuesday, October 17, 2000 7:40 AM
Subject: Re: DML: RE: ABS looooong po'boy intake installed on 4.7 - wow!
> Right. I believe the air hat is a de-tuning device to reduce noise (read
> resonance).
> I don't think any statically shaped intake on an RPM varying machine is
going
> to be all one way to the other 'good' or 'bad'. Also I think there are
> non-resonant based positives to a longer intake that are not frequency
based at
> all; simply that fact that a longer/larger moving column of air provides
more
> inertia to there is overall more pressure at the intake valves.
> Bose concept is not anywhere near the same as Helmholz concept. Bose
concept
> is based more on odd harmonics I believe and 1/2, 1/4, 1/8... wave lower
> harmonics of those odd harmonics or something like that. Helmholz is a
single
> frequency resonant device. The Bose concept somehow gets a smaller tube
to
> resonate over a wide range of frequencies lower than normal, not just a
single
> lower frequency. But I am far from an expert and, like you, are more
wondering
> than knowing.
> Thanks for the input.
>
> Bruce Bridges wrote:
>
> > Marty,
> > Bose Chamber or Helmholz resonator cavity? I havnt seen the 4.7 air hat
> > (yet) but manytimes the designer needs to reduce a natural resonance set
up
> > by the length of the pipe and the "driving frequency" in this case , the
> > pulasations from the 8 pistons. A bad resonance can retard flow and
cause
> > control problems... Or make nice music, like a flute (or a
> > banshee)...depends on the frequency of the standing wave and the
magnitude
> > of the driving force! It pays to do some quick "thumbnail" analysis
before
> > sinking the family farm into a pneumatic design...
> > I should be getting my first 4.7 TB this week to get a good look at its
> > "issues" if any! ...
> > Bruce
> > ----- Original Message -----
> > From: Marty Galyean <mgalyean@acm.org>
> > To: <dakota-truck@buffnet.net>
> > Sent: Monday, October 16, 2000 6:29 PM
> > Subject: Re: DML: RE: ABS looooong po'boy intake installed on 4.7 - wow!
> >
> > > Yeah, you could put it that way. But from my point of view I just
arrived
> > at
> > > the longet section of ABS tubing I could get under the hood and it
happens
> > to
> > > be 'S' shaped. I think mine might be longer than the 'Z', and more
> > turbulent
> > > inside due to more bends and the ABS joins. But yes, I get the same
> > signature
> > > effects. I used the 9" cone. Why? well I figured it couldn't hurt.
And
> > if I
> > > do some TB upgrade later it may end up being more appropriate anyway.
> > BTW,
> > > I was the one who first suggested the air hat was Bose-chambered and I
now
> > am
> > > sure I was incorrect. There are chambers, but I don't think they are
of
> > the
> > > Bose variety. I now believe they are de-tuned to reduce noise
> > (resonance).
> > > Kind of like anit-bose chambers or something. I vaguely recall that a
> > Bose
> > > chamber comes off a tube at a critical point 1/3 down the tubes length
and
> > that
> > > the length of the chamber itself is involved in the equation. The end
> > result
> > > is a small package with deep resonance. Like Danny Devito.
> > >
>
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