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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