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Thanks Ed,
Now that you mention it, I recall seeing
an engine with a very long intake at about a 45 degree angle. I think it was
only for a dyno run. Unusable for just about any application due to its’
length.
I need to re-examine that Renesis
manifold.
Bryan
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Monday, June 21, 2010 10:03
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Pulse Tuning
[FlyRotary] Re: 13B rotary engines
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).
----- 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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