Lynn is usually "right on" with rotary info so I was surprised at the
comment about intake tract always being well below ambient.  This is
obviously not true since it is widely known that a well tuned rotary can
achieve volumetric efficiency well over 100%.   Higher intake tract
pressures are also shown on the chart Paul sent.

The principle behind the higher pressure is very simple and has very

little

to do with sonic waves or resonance.  It is simple inertia.  Air rushes

down

the intake tract at high velocity (there's that dreaded term again) and

as

Newton said, a mass in motion tends to stay in motion until acted upon

by

another force.  The "other force" in this case is the rise in pressure
(above ambient) in the chamber.

My standard bet is $500.00.  Any takers?  :-)

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

I am not willing to bet Tracy but your theory does not hold water.
In a peripheral port engine the intake port never closes. In fact
two chambers are open to the same port at the same time. It must
be exhaust back pressure as in MY theory :-)

Paul Lamar

Just because the port at one point is open to two chambers does not affect
the inertial tuning effect.  The exhaust pulse you bring up does have an
effect (abeit a minor one, as documented in Yamamoto's book) but for the
purposes of this discussion , lets ignore it for the moment.  This exhaust
tuning effect is a BIG deal in two stroke engines but much less so in the
rotary.

Lets start with the conditions at BDC.  Air is rushing down the intake
runner at high speed.  The chamber volume starts to get smaller soon after
this but the air has enough inertia to overcome the rising pressure and fill
the chamber to a higher pressure.  If the intake is properly timed (and this
is the big goal), the air in the intake runner comes to a complete stop at
the exact moment the intake port starts to close.  This is many degrees
after BDC.  The pressure is now at its highest point (as shown in your
chart).  At this same instant, the next chamber is opening and the volume in
it is increasing.  The high pressure in the intake runner is quickly
absorbed by the new intake cycle (which helps fill the next chamber) and
the pressure soon falls to something less than ambient caused by the
expanding chamber and starts the air column accelerating down the intake
port.  Things now progress exactly as they did for the previous cycle.

Just because the port is always open to one chamber or another does not mean
that airflow does not stop and start.  According to every book on the
subject I've read, the harnessing of energy in the air column inertia is
what intake tuning is all about.

Where's the water leaking out of this theory?  :-)

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

Sounds plausible. Perhaps we can come up with a tiny venturi to measure
air velocity in the intake runner.

I am looking at some single board low cost data acquisition computers.
Perhaps I can build or supply some of the hardware required and share the 
cost and labor. I got some questions for you and Finn.

What language do you prefer to program in?
What chip do you prefer to work with? 
Perhaps you can use your Compact PDA's with a
PCMCIA data logger.

Here are some sites. 
http://www.saelig.com
http://www.rp3.com
http://www.jkmicro.com
http://www.micromint.com


Paul Lamar
 
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