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.
>
> Stlaurent Mr Steven wrote:
>
> > You found the 'Z' tube which John designed. The frequency changes from
the
> > Bose chambered air hat (deep mellow sound to a heartier beefy muscle
car) to
> > the Z tube design. On the Z tube it has been noticed the length of tube
> > brought back the lost low RPM feeling during initial tire spinning.
While
> > the Air Raid gained from mid to top RPM range and lost out on the bottom
end
> > range.
> >
> > This is why I switching from this short style to a longer smooth bore
tube
> > to the front left side opening. I will order John 5" cone today that
will
> > be quite adequate for at least 700CFM (the 4.7 TB is rated around 600CFM
> > plus). I have noticed his design cone has a tri-flow into the cone and
will
> > eliminate any turbulence that occurs on the on round cone.
> >
> > I would go for the S version or Z version of the air intake tube.
> >
> > -------------------------------------------
> > Steven St.Laurent
> > Test Engineer
> > Test Branch, GSD, MCTSSA
> > MARCORSYSCOM, USMC
> > 760-725-2506 (DSN 365-2506)
> > Work:mailto:stlaurents@mctssa.usmc.mil
> > Home:mailto:saint1958@home.com
> >
> > -----Original Message-----
> > From: Marty Galyean [mailto:mgalyean@acm.org]
> > Sent: Saturday, October 14, 2000 2:41 PM
> > To: DML
> > Subject: DML: ABS looooong po'boy intake installed on 4.7 - wow!
> >
> > Ok, I should be doing laundry and cleaning up this pigsty, but
> > instead I will lay this on the list. Yes, I am procrastinating.
> >
> > Note: You will need to use a fixed width font for the diagrams to
> >
> > read correctly:
> >
> > The other day I posted that I had replaced the air hat on my 4.7
> > with a curve of ABS and it made 'quite a difference', it looked
> > something like this:
> >
> > 9 |
> > ---+---------+
> > / | | stock
> > 7 / | | air box
> > / --+---------+
> > / / |
> > | |
> > +----+
> > | |
> > +-+ +-+
> > | |
> > | TB |
> > | |
> > | |
> >
> > When my K&N cone came in I installed it where the stock air box
> > normally sits (ala quickd shorty) and it improved the high end,
> > but the low end noticeably dogged. I really didn't give the
> > computer a chance to settle on this interim configuration as I
> > only put about 100 miles on it that way. From my experience with
> >
> > my 240Z I knew that for resonance in a realistic rpm range that
> > it would need to be longer. In the time I had it this way it
> > didn't seem to get much better than the initial improvement:
> >
> > +---
> > 9 | ---
> > ---+---------+ ---
> > / | | K&N |
> > 7 / | | |
> > / --+---------+ ---
> > / / | ---
> > | | +---
> > +----+
> > | |
> > +-+ +-+
> > | |
> > | TB |
> > | |
> > | |
> >
> > Three days ago I put the longest ABS config I could design easily
> >
> > between the TB and the cone and wow, what a difference!
> > Definitely some ram effect occurring at low rpms now! I can now
> > usually spin from a standstill again with the snugtop shell on
> > which I couldn't do right after installing the shell.
> >
> > I used 4 90' small radius bends coming off the TB in roughly an
> > 'S' shape that ended up pointing along the fender well, then put
> > a straight piece on down to the cone that sits at the 'radiator
> > gap'. The 'S' isn't totally flat; this allows it to fit in the
> > space and then angle down to the cone. I had to nudge the tranny
> >
> > dipstick toward the TB to make room:
> >
> > ----
> > / \
> > /| |\
> > /| |\
> > / | K&N| \
> > / | | \
> > / | | \
> > / | | \
> > ---|----|---
> > | |
> > | |
> > ---+--- | |
> > / | \ | | 8
> > 7 / | \ 7 | |
> > / --+-- \ | |
> > / / \ \ | |
> > | | | | | |
> > +----+ +----+ +----+
> > | | | | | |
> > +-+ +-+ \ \ / /
> > | | =+=\ --+-- /
> > | TB | | \ | / 7
> > | | | 7 \ | /
> > | | | ---+---
> > |
> > tranny
> > dipstick
> >
> > I would like to try the following sometime to see if it raises
> > the resonant rpm as I predict (but I think the long one installed
> >
> > is probably ideal for street use):
> >
> > ----
> > / \
> > /| |\
> > /| |\
> > / | K&N| \
> > / | | \
> > / | | \
> > / | | \
> > ---|----|---
> > | | 2
> > +----+
> > | |
> > 4 / /
> > ---+---------+--/ /
> > / | | / 7
> > 7 / | | /
> > / --+---------+----/
> > / /
> > | |
> > +----+
> > | |
> > +-+ +-+
> > | |
> > | TB |
> > | |
> > | |
> >
> > All the numbers are eyeballed (lazy) lengths in inches. Each
> > curve is approximately 7" in length (guestimate based on length
> > of inner and outer curves). So the single curve setup (quickd
> > shorty style) is around ~17", the middle (which I have not tried)
> >
> > is around ~20" and the long one that I like so far is at ~36".
> > This would give them rough basic resonances at 423Hz, 339Hz, and
> > 188Hz. The longer the tube, the lower the resonance (ala tuba
> > vs. piccolo). All these are in the audible range. The
> > calculations are based on sea level speed of sound and a
> > non-moving mass of air (don't know if that matters!). But
> > assuming the air is on the vacuum side of outside air pressure,
> > the speed would decrease and the numbers above would be lower.
> >
> > Here is the simple equation:
> >
> > speed_of_sound (in ft/second)
> > resonance (cps) = -------------------------------
> > 2 * length_of_tube (in feet)
> >
> > Caveats:
> > I don't know how twisted the math gets in the extreme velocity of
> >
> > an intake, nor exactly how to compute the length of the curved
> > sections with regards to air columns etc, but that is the general
> >
> > idea.
> >
> > I am not taking into account the distance from the intake to the
> > intake valves which I am sure is a factor.
> >
> > I am using the equation for a close tube. There are other
> > equations for tubes open at one end and open at both ends. I
> > think the filter is enough of a resistance that it would read
> > mostly 'closed' accoustically (which is why there is a ram tuning
> >
> > effect in the first place). But am not sure whether the valves
> > should be considered opened or closed.
> >
> > But I'm trying to get exact numbers at this point, just a rough
> > idea of the amount of variation possible.
> >
> > So no matter what the details work out to be, there is a big
> > difference in resonant frequency as the length changes.
> >
> > FWIW, DML'ers.
> >
> > Keep on Dakkin',
> > Marty
>
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