Ed Anderson told me he will make a presentation on intake manifold
design using this theory at the up coming Shady Bend Rotary engine
powered airplane fly in  on October 24th, 25th and 26th.
It appears at this time major improvements in intake
manifold tuning MIGHT be possible using this theory.

One of the best internet references I have found so far
is this one.

http://www.ae.gatech.edu/~comblab5/Publications/RobEJASAApril2003.pdf

There may be other good ones. If you find a better one please let me

know.

Read up on the theory so you can ask Ed intelligent questions.

I am sure Ed will jump on here and fill us in some more
before Shady Bend.

Paul Lamar

Thanks Paul, (I think {:>))

    Finite-Amplitude-Waves (FAW) are indeed at the heart of the

Dynamic

Intake Effect (DIE) or "Dynamic Supercharging" as the Mazda Marketers

often

refereed to it.  Found on the NA 13Bs from around 1884 through at

least 1992

or so.   Fortunately, to understand the DIE effect which makes use of

the

characteristic features of a FAW, you do NOT have to understand the

higher

theoretical basis of FAW.  Original solutions of FAW reactions in a
tube/duct involved Hyperbolic Partial Differential Equations (which

are just

about analytically impossible to solve for real world applications)

which

only became solvable with Numerical Techniques (the digital computer).

Now

you may feel comfortable with Hyperbolic Partial Differential

Equations, but

they are pretty tough animals and I, for one, intend to avoid them.

No,

you won't have to bring your computer either {:>).

 So, certainly read all that you are interested in reading about FAW -

BUT,

if you come expecting anything close to the study done in Paul's

reference

above - YOU WILL be disappointed {:>}.  The highest math that you will

need

to understand what I am going to present is high school algebra.  Even

that

is probably not absolutely necessary - but it makes it a bit easier.

Paul makes a good point, the DIE will not make a "silk purse out of a

sow's

ear".  If you don't have a basically good induction/exhaust system to

start

with then DIE won't pull the fat out of the fire. The Mazda engineer's

spent

a lot of time getting a good basic induction system developed to

provide the

characteristics they desired.   Available information I have (mostly
provided by sources from Paul, thanks, Paul) indicates that somewhere

around

a 15% increase is probably the maximum obtainable. My own calculations

also

indicate that  15% approximate power increase over that produced by a

good

induction system.

 For those of you pursuing "Forced Induction" designs this information

will

be of limited  interest.  For those of you which hope to eke out every

last

HP residing in the NA rotary, this will probably get your attention.

Right

now the Analysis only addresses the two rotor engine - sorry you 20B

guys.

I do have some initial thoughts on DIE and the three rotor, but they

require

some more investigation.

 The main focus of my presentation is to show the derivation of the
significant variables that affect the DIE operating points and their
interrelationships (via some simple algebraic equations). Some of it

will

come as no surprise to many of you, but I think other areas will be

eye

opening.  The bottom line is that I have used parametric equations

derived

from my analysis to show the relationship between manifold length and

these

other variables of the DIE and have produced graphs of these

parametric

curves and compared the results with what little specific we have from

Mazda

on the DIE.  So you will be able to judge the validity of the analysis

for

yourself.

So ED's DIE presentation (as contrasted with something Mazda might own

up to

{:>)) will consist of three parts:

A very short lead-in on what got me started down this path

I.  A short overview of the DIE as implemented by Mazda to bring

everyone up

to a minimum level of understanding of the DIE system

II. The analysis and derivation of the variables and equations that

govern

the DIE (this is where the algebra comes in)

III. The comparison of the results of these equations with what we

know from

Mazda about DIE

The presentation consists of approx 65 slides at this point, so bring

your

pillow - this may be the most relaxing time you'll have at Shady Bend.

For those of you who can not make the Shady Bend flyin.  This

information

will be make available to you (assuming that I survive the tomatoes

{:>))

after Shady Bend.  If Paul becomes convinced (yet to be determined)

that the

results are meaningful - who knows, they might even show up on his Web

page.

If they do not then, you will have Paul's de facto assessment of my

Analysis

{:>)

That is all that will be revealed before Shady Bend - thanks for the
announcement, Paul.

Best Regards

Ed Anderson

Ed sent two other web sites that are somewhat more geared towards laymen
but IMHO do not adequately make the connection between organ pipe theory

and Finite

Amplitude Waves. They do mention FAW however. Also IMHO some of their
command of fluid dynamics knowledge is questionable. So I would take this
one with a grain of salt.

 http://www.racetech.com.au/faqinertia.htm

This second web site appears to be an organ pipe simulation. They want to

charge

a bunch of money for it. No mention of Finite Amplitude Waves is made on

the main

page.

http://www.dynomation.com/

At Seven Stock I bought a book called RX8 by J.Yamaguchi & J.Dinkel ISBN

4-947659-02-5

Published by Mazda Motor Corp.

This is a quasi technical book covering in detail some of the intake

manifold

design of the RX8. No mention is made of Finite Amplitude Waves or FAW and

the

Mazda PR department is found of using catchy acronyms when ever possible.
There is no evidence that Mazda ever used this principle in any of the
intake systems Mazda ever built. That is not to say it is not happening
and I think that is what Ed is out to prove.

As I understand it now Finite Amplitude Wave effects occur with precise
changes in runner cross sectional areas such as a trumpet shape or
a bellows shaped duct.

Paul Lamar

Yes, some very interesting things happens when the FAW meets a discontinuity
and those things depend on the type of change in discontinuity such as
increasing/decreasing cross sections, bell shape cross-sections, stepped
cross-sections, etc.  Also what happens depends not only on the type of
change, but the degree of change.  Interesting phenomona without doubt.

You may be correct about Mazda, Paul.  I have seen no direct reference to
Finite-Amplitude-Waves in any of the papers.  The theory has apparently been
around for decades.  The  FAW theory is not needed to explain DEI (although
knowledge that the wave of energy is converted to dynamic pressure when it
terminates at the intake port is crucial - but that can be empirically
measured as Mazda apparently did, showing the intake pressure increase in
Fig 5.0 of the SAE paper due to the FAW pulse of energy)

Want to make one thing clear.  My presentation is NOT about FAW - its about
DEI.  Although I do briefly mention it to explain a couple of its
characteristics that are germane to DEI.  I think 2-3 slides out of the 65
mention FAW.  The presentation is about DEI and the variables involved and
their relationships (equations) of which FAW is only one factor - a crucial
one in that without the FAW effect there would be no DEI, but again only one
factor.

In fact, the only two things I can think of  real importance regarding FAW
and understanding DEI is that the energy wave travels at the Speed of sound
in the manifold and that it generates high pressures at  its termination end
(near the intake port). So if you consider those two characteristics
adequately explained by other theories and can accept it without the need of
FAW theory, then you don't need FAW to explain DEI at all.

So not out to prove anything about FAW and DEI, just to present the results
of my analysis -  which of course, anyone is free and welcome to form their
own conclusions about.

 From my initial analysis, it appears that if you want understand how the
Dynamic Chamber functions to broaden the DEI torque curve, then there are
several other characteristics of FAW that are germane to the Dynamic Chamber
operation.   But as the Dynamic Chamber is not required for DEI  that is not
part of the DEI presentation.  I assume the function of the Dynamic Chamber
can possibly be explained by other theories - don't know, have tried a
couple and just haven't gotten far with them.    But, the FAW predicted
reaction to the Dynamic chamber appears pretty straight forward as far as I
can see and does provide an explanation for how the chamber broadens the
Torque curve.

Since I don't have anymore on the simulation than what you see on the 2nd
web page and what is in the book  I have, I can't comment.  But, the
simulation is generally described in the book and the book claims it is
based on FAW.  However, I'm not going to spend $600 to find out, nor do I
have any stock in the company{:>)

Again, the focus of the presentation is DEI not FAW.  Anyhow, I am off now.
Won't be back online until Sunday or Monday.

Best Regards

Ed Anderson

A slug of air moving down a tube suddenly encountering a closed intake port will 
increase in pressure due to just plain old inertia effects. It is like a ballon filled
with air and will bounce like a ballon.  As the slug of air travels
back along the tube a drop in pressure will occur behind the slug. Particularly
if it encounters an increase in tube cross sectional area such as a sudden
opening. Nature abhors a vacuum so air rushes in to fill the vacuum in 
the tube starting another slug of air flowing down the tube. 
The same effect will occur if the slug encounters a T a Y or a branch
in the pipe.

This happens as long as the port remains closed. If the port opens just as 
the new slug arrives the engine will benefit from the increased air 
density of the new slug. It will draw that air in and then some causing
the start of a new slug at the other end of the tube. Generally speaking 
the slug travels at the speed of sound.

A slug of air is high pressure and high density by definition. Air molecules 
are always moving around locally. They move faster and run in to each other 
and the container walls more often when the pressure is increased. This is 
because there are more air molecules in a smaller space. 

This is called the Kinetic Molecular Model Of An Ideal Gas.

KMMOIF for short :)

An analogy is the dynamic pressure phenomena. As you move a flat plate 
perpendicular to the air stream pressure is built up on the plate.
This we recognize as the aerodynamic drag phenomena.

Now if the tube is of a non uniform cross section like a trumpet
not only is the inertia of the air increasing the density and pressure
but the decreasing cross sectional area of the tube is also tending to increase
the pressure and density. This I think is the main Finite Amplitude Wave effect.
The question remains. Will the engine really get more air?

I also want to point out there are no dynamic chambers in the 3rd gen
and RX8 intake systems. Just T's, Y's or branches in the runners.

BTW Back in the days when I studied Physics our text books were not 
well illustrated compared to today's standards. 3D computer programs
have gone a long way towards making physical phenomena much
easier to visualize. I highly recommend  University Physics
by Hugh D. Young. ISBN 0-201-52981-5


Paul Lamar
 
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