Paul, throttle response of our peripheral port engines was very good on
 the
 ground and in the air, and at any point throughout the operating  range.
 No
 discernible lag. No stumble with throttle advanced from  idle slightly or
 full throttle when on short final, etc. so made it  very nice to fly.
 Idle
 speed approx. 1000-1200 engine rpm. But we  had the throttle shaft and
 plates located inside the rotor housing.  Although locating the throttles
 in
 the rotor housings is probably  the optimum for response and idle speed,
 it
 involves a lot of work.  Putting a slide or throttle-body with
 plates/shafts
 just outboard of  port probably next best location.

 Steve Beckham

 As  I recall Mazda placed the injectors close to the P-port on the
 Lemans
 engine for throttle response reasons as it is very important  when road
 racing.

 http://www.rotaryeng.net/Mazda_R26B_US.pdf

 Also it might be a  good idea to use a Megasquirt in this application.
 The 555 system  and Tracy system has no provision for rapid engine
 acceleration.

 We did discuss it at one time by putting a special switch on the throttle
 knob  to
 temporarily enrich the mixture.

 "Basically it is  short stroke pancake air cylinder mounted on the slide
 throttle
 knob  inside the cockpit with a small air hose connected to the back
 side  of the diaphragm in the Tillotson type carb. The increased air
 pressure
 will inject an extra shot of fuel and open the supply  needle valve at
 the
 same
 time. When the knob is released the  diaphragm spring will slowly restore
 the diaphragm
 and close the  needle valve again.

 Something like a 1 inch bore (2" OD)  cylinder with a .5 inch stroke
 or smaller should do the job. A  spring inside the cylinder will restore
 the
 stroke after the knob is  released. A one way valve on the intake port to
 the cylinder
 will  fill the cylinder with air."


 Paul  Lamar


 Paul and group,
 Every racing and street EFI that I have encountered has a throttle
 position sensor. The rapid opening of the throttle at low RPM should
 automatically
 enrichen the mixture. Since the injection is a demand system based  on
 RPM
 of the pump, and the stroke or the time of opening the injector, the
 throttle response should be better than any carb system. Airflow
 performance  type
 systems use the differential between the servo pressure and the inlet
 pressure to do the same thing. Hilborn style systems connect a valve
 directly to
 the throttle shaft that does the same thing. (I know Paul knows this
 already but  it should be built into any EFI system.) The basics of fuel
 injection is so  intuitive that it is supprising that the carburetor came
 first.
 Even a system  without a throttle position sensor should have programing
 ability to richen  using the map sensor. Older alpha-n systems used only
 a
 TPS and
 RPM with a  programmed fuel map. We are talking about making a injector
 pump like used in a  carb. This shouldn't be needed in a EFI. Just my
 $0.02.
 Bill Jepson



 --------------------------------------------------------------------------------
 Thanks Bill. Your review reminded me that I should have included in the
 original note that our system reviewed was not electronic.

 We started out with an original design system that used some Hillborn
 components such as pump and valves.  On the second generation SuperLight
 engine in the early 1990's, we wanted to use a proven, available system,
 so
 adapted Don Rivera's complete Airflow Performance system developed from
 when
 he worked for Bendix.  But before our application, Don had already
 successfully adapted it to Mazda race engines built and campaigned so well
 in the factory-backed rotary cars built and driven by Roger Mandeville and
 his team.  Don also worked with Jim Mederer in his work using the Airflow
 Performance system.  Roger used Don's system up until the later refinement
 of the British and similar electronic race car units were sorted and
 available.

 For the conversion Mazda engine intended for production in the late
 1990's,
 we tailored Don's system to our engine configurations by making our own
 little venturi for optimum packaging in tight cowlings, with the verturi
 providing the inlet to the intake plenum to provide signal to Don's
 servo/controller.   We machined a backside billet cover which sealed the
 servo diapraham and aso had incorporated holes for bolting to the engine
 via
 existing Mazda provision in the housings.  The servo was mounted on the
 other side of the engine opposite from the plenum, so we could
 interconnect
 the servo with the throttle and throttle shaft arms with a short
 heim-jointed arm.  So when you moved the throttle lever it simulataneously
 moved the servo arm.  In standard form, Don's unit for reciprocating
 aircraft and race cars comes with verturi and servo/controller all cast in
 the same piece.

 On the newsletter I've seen some discussion of driving a fuel pump with a
 Gilmer/tooth belt.  Originally we started out with the Hillborn-based
 system
 where the fuel pump was driven by a Gilmer belt.  When we started dyno
 testing engines, we always did so with the propeller reduction gear
 installed--water brake dyno to start and later when we built the dyno to
 for
 using a club/propeller.  The engine had no flywheel, just a very light
 unit
 to hold the starter ring gear.  Of course the combined torsional factors
 are
 significantly different than in a car.  In early testing, before we got
 our
 act together and understood and addressed the torsional and other issues,
 at
 certain speeds on dyno pulls, the Gilmer belt would blur and jump off the
 Hilborn pump pulley; skipping teeth and (sometimes) reattaching when the
 rpm
 dropped with related misfire. Something to think about when considering
 different fuel injection pump/engine configurations.  These misfires could
 combine with other factors to destroy gear teeth and this included rotor
 gears/stationary gears.

 This early engine had a plenum and throttle plates located way up at the
 front of the intake runners which ranged from 18"-2 ft long (our target
 rpm
 was 5-5,500 rpm). Because the throttle plates were so far upstream, the
 idle
 and throttle response was lousy but made 200 h.p. with dual side port
 aluminum housings @ 7,000 rpm.  We then switched to a peripheral port
 system
 that experimented with various port shapes, port timing and runner dia and
 length.  These engine outputs ranged were engineered and performed well at
 lower rated rpm:  180+ hp @ 5500 and 200 @ 5900 rpm; more at higher rpm
 and
 limited in flight to 7,000 rpm for races.

 In conclusion, it seems natural for folks working on electronic systems to
 turn their noses down on a mechanical, constant flow systems such as Don's
 and the Bendix and Continental, as crude and simple.  They are indeed
 simple, but they are not crude, and the result of over half a century of
 development and use.  Obviously an electronic system has more
 sophistication
 in design and potential for some degree of performance increase at cruise
 and altitude.  In the use of  homogenous-charge rotary engines in aircraft
 where we operate most of the time at a relatively fixed power setting
 (cruise), there are important basic questions for each builder.  Are the
 relatively small gains of electronic injection, at this stage of
 development
 for home-grown efforts, more than offset by installation and tuning
 complexity, and lack of development and reliability?

 We looked long and hard at electronic systems and used them on Chevy, Ford
 and Nissan engines built in the shop for IMSA  and other applications.
 There
 were the inevitable major development and teething issues as the systems
 were developed and tested.  We see that same cycle today with homebuilt
 aircraft.  It goes without saying that, unlike a race car which can be
 pulled off course when it fails, the airplane driver has no such luxury
 when
 the damned thing fails.  Despite this admonition, we worked on various
 electonic system designs for our rotary aircraft engines over an eight
 year
 period up until late 1997, with the folks who developed the race car
 systems.  But for proven performance, flight safety, ease of installation
 and operation, we found nothing surpassed Don's Airflow Performance
 system.
 Even today, over 10 years later, using that critera, it can be argued none
 of the electronic systems available to homebuilders today can presently
 measure up to that combined critera at this stage of development.  Don's
 system is no doubt more expensive than a home grown electronic system. But
 we found it totally without fault--nuts on reliable, easy to install,
 responsive, proven and simple, and he works with you to tailor and tune it
 to each application; including in the airplane.  A lot to be said when the
 goal is to get the airplane flying, perform well, often and reliably...and
 especially when you are not an electronics engineer experienced with
 engines.  Apologize for the verbosity.

 Steve Beckham

 Steve, if you ever do a book on the history  of Power Sport I have saved
 all your
 messages.


 Paul Lamar

 Craig Taylor here;

 After reading Steve Beckham's interesting letter above, I have a few
 thoughts.

 For aircraft rotary applications, the timing of the fuel squirt from an
 individual injector
 shouldn't be critical.  After all, the air flow into the chamber does vary
 over time but it never
 actually stops.  Therefore I can't help but wonder if a continuous
 injection system based on RPM and
 MAF wouldn't be close to optimum.  It should also be easier to implement a
 "limp home" mode than
 with an electric pulse injector.  Possibly a transfer switch and a control
 knob to hand vary the
 fuel flow would suffice.  It could be purely passive and work as long as
 there was fuel pressure.
 An electrically variable valve coupled to an inline fuel flow meter would
 allow well controlled
 fuel flow.  Varying the flow proportional to RPM would give a first
 approximation of a constant
 air/fuel ratio.  Adding MAF as the modifier of the RPM signal would give a
 tighter control, of
 course.  Finally, using an exhaust oxygen sensor would allow constant
 speed, level flight tweaking
 to maximize economy.  Maybe.  The original intent of the oxygen sensor
 was, I believe, to minimize
 HC emissions from auto engines.  So it may not be the best indicator of
 optimum mileage for an airplane.

 Just some thoughts.  A rotary engine for aircraft use is just a
 completely different beast than a
 piston automobile engine.  ESPECIALLY when it comes to sub-1000 RPM idle.
 Why spend lots of time
 and money optimizing low speed and/or low load operating conditions?

 Craig Taylor


 Nobody idles them much less than 2000 RPM as the gear box will not
 tolerate it.
 The prop is only going 700 RPM. The same as an air cooled aircraft engine.

 Klause built a limp home mode fuel system consisting of a gravity feed
 header tank
 and a pet cock. Almost exactly like the Wright brothers used. The feed
 tube was merely
 plumbed to a hole in the intake manifold. Once you got it stabilized you
 kept that
 throttle opening until you were ready to dead stick it in. You could use a
 hand pump
 to keep the header tanks full.



 BTW every body should practice
 slips. Highly useful for getting it in the first time :)



 Paul Lamar




 Along those same thoughts, here is a nice little flow sensor designed for
 gasoline and reasonably
 priced.  Well, $250 seems reasonable to me compared to other instrument I
 have seen.  Se the
 attached PDF.

 Tom Craig

 Here is a cheaper way to do it if you are using PWM EFI.

 Paul Lamar


--------------------------------------------------------------------------------

Thanks for note Paul.  As to the points raised in emails, here are a few
additional notes.

The reason we went to the trouble of locating the throttles in the rotor
housings was based on our testing of the first engine with throttles located
a distance from the ports.  We felt it imperitive to provide the best
possible off-idle and response throughout the operating range, and when
operating with larger diameter propellers which provided superior thrust.
This throttle location had been very successfully used by Mercedes in their
C-111 peripheral port rotary engine program to make the engine responsive at
the lower ranges so important in a car.  So we thought it was worth the
effort to provide the most superior, safest operation in flight.  When we
incorporated this design into our engines using modified Mazda rotor
housings, it proved a very helpful operational feature.  We always did fully
power off approaches with large fixed pitch propellers in the early years
with tall reduction gear ratios.  The throttle placement provided very
helpful to us when flying over the river into bad wind shear and turbulence
right before you got to the end of the runway at the shop.  There, in the
summer on a hot day, when you hit the shear, the bottom abruptly dropped out
on short final, it would take the throttle so quickly and smoothly that it
was as if it had an electric motor.

Also, we originally had that large 86" wood, fixed pitch prop of well over
100"of pitch (125" when we went down to 74" dia in later versions as speed
increased, with various reduction gear ratios when using planetary units.
So even at low airspeeds and very low engine rpm those props produced thrust
to pull the RV-4 along.  It would float for a long time, especially when it
got into ground effect on landing.  It never had the wingtips installed
because the wing loading was so light.  It weighed 850 pounds.  Also, we
often landed on short, unimproved airstrips and fields, always with power
pulled completely to idle.

The issue of low idle speed and smooth, responsiveness to throttle settings
is also related to issues regarding the reduction gear. The low engine idle
was possible with absolutely no gear rattle when we developed the later
planetary reduction gear units with pendulous dampers.  Following that
development, the challenge became to design a reduction gear that eliminated
completely the need for ANY dampers or isolators of any kind, so we could
further reduce parts count, improve safety and lower costs for consumers.
This approach was possible only becasue of the Mazda's exceptionally short
and stiff eccentric shaft.

These developments led to the design, testing and refinement of the straight
cut, torsionally stiff  internal spur gear reduction unit which would work
at any engine rpm within the operating range with no dampers, absorbers or
isolators. When you were at the house you saw  our preproduction unit which
Steve Weinzeral further refined in his design that Ray Richardson machined
at Ratech Machine under a "Powersport Aviation" name.  Steve and Ray
incorporated a full CNC-produced power section adaptor.  Ours was cast.
Steve retained a rear thrust ball bearing as we did in the second prototype
unit.  It was far superior to the original prototype thrust arrangement.  In
the front prop shaft between the internal spur gear and the prop flange we
used a plain bearing similar to the Lycoming front crankshaft bearing, but
Steve W. opted for an additional super-precision ball bearing at the front
of the prop shaft.  He retained our use of a  pinon support bearing.  Our
first prototype unit did not have a pinion support bearing and it quickly
became apparent we needed to incorporate one in our second prototype.  It
significantly improved the design.

Overall, we felt this approach to a reduction gear was a successful
application of a simplified "less is more" design, and a major advance and
logical culmination of our years of development.  In this form it was an
extension of the simplicity of the rotary engine design and our driving
mantra that if it is not there it cannot wear, require maintenance or fail.
Based on our experience, the most difficult design challenge is to simplify
while improving strength and efficiency.

As to the throttle placement, plans were to later transition the throttle
plates just immediately outboard and attach the throttle body to the
periperal port inserts to reduce costs further for customers at what we
hoped would be negligible degredation in idle and throttle response.

Steve Beckham



Steve,

Thanks again for explaining all of this background.

I am interested in knowing how wear in the gear seat manifested
itself.   Was there increased lash?  Could that be adjusted out?  Did
increasing lash cause any change in operation?

Are you familiar with the gear reduction on the Continental GO300?  I
believe that's an external spur gear..


Regards,

Matt-