-------- Original Message --------
Subject: Intake manifolds
Date: Fri, 22 Jan 1999 03:12:06 -0800
From: Paul <rotaryeng@earthlink.net
To: z <rotaryeng@earthlink.net

Paul Yaw wrote:

 Hi everybody,

 I would like to point out a few things concerning intake tuning that I
 think are inaccurate, and expand on a few others.

 For some reason that I cannot explain, whenever I verbally disagree with
 someone I tend to feel that I am being argumentative and abrasive.  As a
 result, I normally keep my mouth shut if I disagree with someones
 opinion.  Because of that weird personality quirk, I had not intended to
 respond to this.  Then it occurred to me that I certainly wasn't doing
 anyone a favor since the whole point of this mailing list is the
 exchange of ideas.  So here goes.

  Tracy Crook wrote:

   I think we must remember there are two different methods of tuning at work
   here.

   The tuned pipe manifold that has been the major topic of discussion on this
   thread depends almost entirely on inertial effects

 A "tuned pipe" refers to using the naturally occurring organ pipe
 resonance to "supercharge" the engine.  Inertial supercharging is an
 entirely different matter, but both methods rely on increasing the
 pressure at the intake port during the period from bottom dead center to
 intake port closing.(Approximately 70 degrees after bottom dead center
 on a 6-port 13B)  The purpose is to create a pressure differential
 between the intake port, and the chamber so that the chamber will
 continue to fill even though its volume is decreasing.

  (once the air starts
   moving in the pipe it wants to stay in motion) and the resonant frequency of
   the pipe.  (major simplification here) This is certainly a legitimate method
   of increasing volumetric efficiency but it has certain drawbacks.  One is
   that the improvement works over a small range of engine speeds (and as has
   been pointed out, actually hurts at others) and the pipe length is rather
   long at the engine speeds we want in aircraft use.

 Regardless of the length of a pipe, these pressure waves will ALWAYS
 exist.   However, the pressure waves will typically be stronger in a
 longer pipe of the same diameter.  The reason for this is that upon port
 opening the mixture in the intake pipe must be accelerated to initiate
 flow.  A longer pipe has a greater mass of mixture to be accelerated,
 and so will require more energy to do so.  This results in a stronger
 initial pressure drop in the chamber which is what initiates the
 pressure wave in the first place.  In the case where the pressure wave
 is initiated by the pressure increase after intake valve closing, the
 same thing applies.  The greater mass of mixture results in a higher
 pressure which of course initiates a stronger pressure wave.  Mazda, in
 their SAE paper concerning the "Dynamic Chamber" completely ignores the
 effect of the initial low pressure wave initiated at intake port
 opening.  Using long pipes for the purpose of harnessing high amplitude
 pressure waves will most certainly have the effect of lessening the
 power at some speeds, and increasing it at others.


   The other method (the one I designed around)  is the "Dynamic Chamber"
   effect  as described in Kenichi Yamamoto's book.  I reprinted the charts
   showing how this worked at the end of my conversion manual.   The full
   explanation of this effect would require a much longer message than this but
   if you study and understand what is going on here, you will see that it
   depends on the fortuitous timing between the two rotors in the 13B.   (note
   that this will NOT work on a three rotor 20B due to the different timing
   relationships between rotors).   One really nice thing about it is that it
   is a broad band effect.  It works at ALL engine speeds and has none of the
   "dead spots" of the tuned pipe.

 The "Dynamic Chamber" effect also relies on pressure waves traveling at
 the speed of sound.  For this reason it will be "in tune" at some speeds
 and "out of tune" at others just like the pressure waves in an
 independent runner manifold.  The purpose is to have the pressure waves
 arrive at the intake port at the proper time.  Since the speed of sound
 does not increase with engine speed, this can only happen over a very
 narrow rpm range.  If you look at SAE paper 831010 you can see that the
 engine actually had better volumetric efficiency at 3000 rpm with a
 separator in the plenum which kept each rotors pressure waves separate
 from each other.

snip......... More stuff from Tracy.


 In last months tech. article I went into a fair amount of detail on
 pressure wave tuning.  As it is written, it is meant to be applied to
 the exhaust system, but pressure wave theory applies to intake and
 exhaust in the same manner.  You can find the article at
 http://personal.riverusers.com/~yawpower/jantech.html


Good explanation of tuning effects Paul.
Thanks.

BTW what is the title of  SAE paper 831010?

The proof of the various theories will be discovered in the long
run with actual performance of airplanes.

I might point out we don't give a fig about how broad the torque
curve is. The chart below is from Theory of Flight the classic
book by Von Mises. Pre is power required and Pav is power avialable.

Pav is mostly a function of the propellor. A variable pitch prop
or constant RPM prop (constant max HP) would convert the Pav to
almost a horzontal line. This chart is for a fixed pitch prop.

Paul Lamar

The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org


===============================================================================
LAST 8 years later :)
==============================================================================
------- Original Message --------
Subject: 13B intake
Date: Tue, 19 Jun 2007 10:39:51 -0700
From: Rotary Engine <rotaryeng@earthlink.net>
To: AARotary Engine <rotaryeng@earthlink.net>



Paul,
Okay, I can't stand it! I have a beautiful airplane almost ready to fly
and I don't want to skimp on the power plant. I ordered what I think I
need to build the runners and dynamic chamber, but now I'm not sure it
will all fit under the cowl. How important are size and shape of the
chamber? and I am shooting for 28inches on the runners right? How about
the significance of where I install the injectors?

Sorry I'm a pest!

Steve Denny

No problem Steve. I'll work with you until you have something you like.
Thats is why I am here.
Forget the dynamic chamber. The runners would have to be only 12 inches
long
as that is probably very difficult to convert to actual hard ware.
The Mazda versions are designed for torque at 3000 RPM which is useless
in an aircraft.  Use some 2 inch OD tubes on the outer ports
and 1-3/4 OD or 1-7/8 OD on the two center housing ports. Make
them about 28 inches long but design it so you can change the length
a few inches one way or the other. Put a plenum on the end.
If you use a 4 inch round tube plenum and weld the runners in you get
a fair transition so you may not need trumpet mouths on the
ends of tubes where they enter the plenum. Your throttle body
looks fine. Cold ram air is very important. However if you
have a dusty runway you will need a filter some place.

The injectors can go anywhere. There has been reported a slight
BSFC advantage if the injectors are mounted out near the plenum.
Others say no.... mount them close to the engine.
This Ford Escort manifold is the right idea but the runners
are too small.

Put a power bulge on the cowl if necessary :)

Paul Lamar ...No rotor no motor.


Paul,
Oops! Sorry I fat fingered the keys and sent that last one by mistake.
Thanks for the info. It sounds easy enough. I plan to use thin wall 4130
so I can weld it. I'm not sure what to use or where to look for the 4".
Should the pressure taps and temp sensor for the controller be mounted
in the plenum then?

Steve

Yes on mounting the pressure tap and temp sensor on the plenum.

BTW you might want to run it the way it is. I am sure you will
get at least 150 HP. Later on after you fly it you can make
some improvements in engine HP.