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BW, as best I recall (don't have a Renesis) that
small chamber is simply a "transfer chamber" to get the pulse from one intake
tube to another.
The DIE effect that Tracy mentions relies on a type
of pulse called a "Finite Amplitude Wave (FAW)" - this wave behaves different
from traditional sound waves and makes a 125 db sound wave seem lik a very tiny
soundin comparison. These wave shatter metal not to mention ear
drums.
There are several "tuning" techniques which attempt
to make use of these Finite Amplitude waves in induction systems. Mazda
has been one of the most successful attempts in part due to its unique
construction (no valves) and the rapid generation of these waves in the
intake. In the older 13B anytime the intake port opened, the still present
exhaust gases would burst forth and produce a shock wave ( FAW
pulse). If the intakes were tied together and of the proper length - at a
specific rpm the pulse generated by the opening of the intake of one rotor would
travel through the intake to the intake of the 2nd rotor. It was designed
to arrive just as the intake port was closing.
When an engine (piston or rotary) starts its
compression stroke, the intake remains open for a period - during this period
the compressiing piston/rotor pushes out some of the mixture its already
"sucked" into the chamber. Typically the value for this mixture pushed out
during this "Reversion of flow" amounts to around 15% of the amount already
"sucked" in.
So if the FAW Pulse arrives at the right time most
of its dynamic energy is converted from kinetic energy to a localized increase
in pressure right beside the closing intake port. If all goes well it
prevents most of this reversion. In fact, Mazda found a 15% increase in HP
at 6000 rpm using this knowledge.
However, it is generally only significant for one
rpm - or if you do like Mazda and have a valve to change the length of the
intake for this pulse, you may get two sweet spots at a lower and a higher
rpm.
Since PP are not interconnected the approach Mazda
used on the N/A 13B side ports won't work as is.
However, due to the properties of the FAW pulse
when it encounters a change in cross sectional area, the pulse tuning technique
could theoretically be used on a PP. Since you want a increase in pressure
as the port closes, and since the FAW pulse will reflect from an opening into
the atmosphere (Plenumn box also) - if you made your PP tube a specific length
then at some rpm (which can be calculated) the pulse will bounce back from the
plenumn and reach the intake port at exactly the correct time.
That said when one makes the calculations (as best
I recall from a few years ago - so don't hold me to exact figures), you would
find that say for the peak to occur at 6000 rpm - your PP tube would need to be
around 48" long. High target rpm would result in smaller lengths
required.
Then again, that length (whatever it is) is only
good at one RPM to get the effect.
In my case, I spent 3 months just doing the
analysis to derive the equations for the old 13B. Since my primary
objective was power on take off - (I really don't care about top speed as I
don't fly there - too expensive {:>)), I did not mind the restriction to one
rpm.
So my DIE intake is tuned to give maximum power at
around 6000 rpm (My static for take off swinging a 74x88 prop). I may get
up to 6200 rpm static on a colder day as the sweet spot is a function of the
speed of sound (among other things) which changes with OAT
temperture.
In my opinion (and that is all it is), if I were
going PP, I would probably not spend much time considering DIE (or Dynamic
Chamber -- which is not quite what most people think it is).
FWIW
Ed
----- Original Message -----
Sent: Monday, June 21, 2010 8:38 PM
Subject: [FlyRotary] Re: 13B rotary
engines
Thanks Tracy,
I didn’t realize the
plenum would have that effect.
The stock Renesis
seems to have a chamber prior to the valves that create the DIE, but I guess
it is too small to be called a plenum chamber.
BW
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Tracy Crook
Sent: Monday, June 21, 2010 8:12
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 13B rotary
engines
I
hate to ask, but what about the Dynamic Intake effect in the PP with a
traditional log-type manifold?
If you think
about the meaning and function of the Dynamic effect, you will see that it is
mutually exclusive with the traditional log-type manifold. the
'log' is a plenum chamber which inherently damps out the dynamic waves and
reflections in a DIE intake system.
The timing, length, etc would be
different than for the sideport DIE setup that Ed Anderson did so much work
on. I won't even pretend to have any idea what the proper parameters are
for a PP DIE setup.
Tracy
On Mon, Jun 21, 2010 at 7:44 PM, Bryan Winberry <bryanwinberry@bellsouth.net>
wrote:
Yeah,
I just saw those MP
taps for the oil injection on another site. I’m no expert, but that
seems like an odd place to gather MP data.
I only asked about
the slide throttle, I certainly had not decided that it was the
answer.
Sounds like you
recommend the traditional TB – manifold – runners setup for the PP as
well.
I hate to ask, but
what about the Dynamic Intake effect in the PP with a traditional log-type
manifold?
Bryan
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Monday, June 21, 2010 7:29
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: 13B rotary
engines
I have purchased
the EC-3. Will this make any difference in the difficulty of
tuning? Is it a good choice for a PP
setup?
I’d imagine I
should aim for around 7500 rpm for a
RD-1C.
Bryan,
Mark (the Mustang II w/ pp 13B) used an EC2 on his engine and eventually got
it running pretty well but it was a MAJOR pain getting it to work with that
slide throttle since getting manifold pressure was hard to do since there IS
NO MANIFOLD when using that slide right at the port. No one seems to
consider these 'details' when planning their installation. I'm of the
same opinion as Bill on the slide throttle- Why the hell do it?
Mark eventually got a usable MP signal by taping into the oil injection ports
in the rotor housing but that's not ideal.
BTW, several people
referd to Mark's PP 13B as a Renesis PP but I thought it was a 2nd gen
13B. I could be wrong. Pity that the airplane was lost in that
ground accident, I had not heard about that.
Tracy
On Mon, Jun 21, 2010 at 7:13 PM, <wrjjrs@aol.com>
wrote:
The importance of
any system that you use will be, DO YOU UNDERSTAND IT? Have you ever
tuned an engine using a carb, or FI yourself? Tracy's system seems
like a good one for the price. I have not used Tracy's EMS but it has
been effective for the guys that keep at it. A good fuel flow and mixture
meter are top tools for determining where you are. I believe those are built
into the EC-3. Remember, while it won't be changing while you run the engine,
the intake and exhaust are just as "active" parts as ignition and injection.
My advise would be to be sure that you triple check all your wiring before you
install it. Too many of the guys have run into problems in their wiring. Be
sure you are dealing with a genuine tuning problem and you will be miles
ahead.
I have purchased
the EC-3. Will this make any difference in the difficulty of
tuning? Is it a good choice for a PP
setup?
I’d imagine I
should aim for around 7500 rpm for a
RD-1C.
-----Original
Message-----
From: Bryan Winberry <bryanwinberry@bellsouth.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, Jun 21, 2010
3:50 pm
Subject: [FlyRotary] Re: 13B rotary
engines
I have purchased the
EC-3. Will this make any difference in the difficulty of tuning?
Is it a good choice for a PP setup?
I’d imagine I should
aim for around 7500 rpm for a RD-1C.
As a reference the
original Powersport 13B P-port is rated at 210 HP normally aspirated. The fuel
flows are very similar to any other engine producing that level of power.
Steve tells me that they were seeing FF very comparable to an angle valve
IO-360 producing identical power. This engine was dynoed with butterfly valves
in the housing. These p-ports were 1-5/8' diameter optimized for 6000
RPM. The engine would rev higher but you were already at peak power anyway.
Larger ports will make more power at higher RPM. Tuning will become
more critical with the larger ports. A personal anecdote here. I built a
high reving motorcycle engine in 1978 with all the "best" parts at the time.
The engine was unreal at high revs, but if you transitioned to anything below
4000 RPM by shutting the throttle off and quickly opening it again the engine
would "catch" or hit an RPM plateau and would rev no higher. In fact
the engine would die if not returned to idle! This horrible malfunction was
TUNED OUT later, and the solution was surprisingly simple, however difficult
to find. The key here is that many people underestimate the job of
installing and tuning p-ports. There are two aspects, first the initial
install being sure there are no leaks . Then second, and most overlooked is
that the system must tolerate the heat cycles of a high power engine without
DEVELOPING NEW LEAKS for a long time. Powersport used an insert with o-rings
sealing the port. O-rings or other elastomers work much better than epoxy on
long-term sealing because there are different expansion rates between the port
and the epoxy. On a car you can usually get away with epoxy for a while.
An aircraft is a different animal. The aircraft engine needs to tolerate
80-100% power for long periods and then long cold-soaks on the ground.
The rotary is mechanically tough enough but you need to design your subsystems
like a race car that will see a 500 mile long straight-away! When
Paul Lamar ran one of the newsletter guys P-port Renesis at MazdaTrix, They
got great numbers, but only after changing to an intake that MazdaTrix had
spent lots of time tuning. P-ports will run great, and even idle well if not
too oversized, but don't expect the tuning to be real easy. Remember you are
designing a new intake, exhaust, and the equivilent of a new cam timing all at
once. The rotary is very much like a two-cycle in that respect. The results
can be very worth while if you understand the difficulty
involved.
Not all P-ports are
equal.
Talk to Bill Jepson
( on here) about availability of new
P-ports.
All this talk of
additional power coupled with an easier intake design has me thinking I
should probably go this direction with my Renesis. It’s still on the
stand after rebuild.
I haven’t
constructed the manifold yet
anyway.
I assume fuel flow
will be higher than normal?
Is slide throttle
best option?
Need to search
archives I guess.
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lynn Hanover
Sent: Monday, June 21, 2010 12:15
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 13B rotary
engines
In a message dated 6/21/2010 11:03:01
A.M. Eastern Standard Time, rv-4mike@cox.net
writes:
Thanks for the
feedback Lynn. Unusual to see a "poor port design"
actually aid performance.
It is not obvious until you start
graphing the open and close events, but the side port which uses the side of
the rotor as a shutter to open and close the port, offers Mazda great
latitude in port timing. In the periphery ported engine (both ports)
it is impossible to arrive at zero overlap, and have an engine that will
produce any power at all. The apex seal does not close off either port at
all, it just valves gasses in one direction or another.
In addition, the overlap of the
periphery ported engine is far more effective flow wise than overlap in the
side ported engine. One apex seal is above the intake port when the opposing
apex seal is below the exhaust port. Flow between the two is
unobstructed.
So, at low RPM you get fresh mixture
leaving through the exhaust port, and combinations of burned and unburned
fuel and exhaust gasses flowing partway back into the intake
runners.
This reduces the low RPM output to the
point that the engine seems quit docile, and is easy to drive around in the
car, slowly, or possibly taxi in an aircraft. This would make off idle
tuning data useless as there will be fuel burning right on top of the EGT
probes, and unburned fuel reaching the F/A sensor.
The engine will act along the
lines of a piston engine with a long duration cam. When the engine reaches
its happy RPM where all of the mixture is burning inside the engine, it will
step up on the "CAM" and you will see what
a good idea this was. Use slow throttle inputs until you find the "WOW" RPM,
and be ready with all available rudder.
When we first ran a factory periphery
port engine, we found that there were places on the track that would not
allow full throttle. This with 11" wide slicks. Thank Heaven for rev
limiters. The driver reported the rear end getting real loose cresting hills
and bumps.
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