I just ran across this data on the 2nd gen RX7 mass airflow sensor.
 Bosch wrote it up as part of the L jetronic injection system manual.
 I suspect it is made by Denso under license and installed
 in 1986 to 1991 RX7's. I don't think it is a computer.
 I think it is similar to a 555 system. All hardware and no
 software.

 Perry Mick has been flying this system for years in his Long EZ
 with hundreds of hours.

 It is very reliable. He has tricked the ECU into thinking it is
 still in car. He has even installed an RX7 instrument panel
 in the cockpit.

 There are probably over 100,000
 of these systems out there. They are real cheap I suspect.

 Paul Lamar

 Paul,
 This may not be doable for Aviation and I have no doubt that someone will
 tell me why, however all ideas should be explored if only to eliminate
 them
 IMHO. Now some motorcycle carbs have floating slides whereby the density
 of
 the incoming air varies the slide compared to the throttle position - for
 altitude compensation. I can't remember exactly how this is accomplished
 by
 lifting the slide with the incoming air. There is a sloped face which is
 supposed to have a critical angle to accomplish this task. It may be
 there
 is a calibrated spring that air density is pushing against.

 This is the simplest solution air density adjustment I have heard about.
 For your consideration.
 George ( down under)

 George,
 My motorcyle has these. Tuned for sea level, it runs rich when going over
 the Sierra's.
 If you tune it for Denver, pings like crazy at sea level.....
 The slide is lifted pulling the mixture needle out of the jet by the low
 pressure area created by the air flowing by an orfice in the bottom of
 the
 piston.
 The top of the slide has a larger piston (or diaphram) and the vac on the
 top side pulls the slide up. But they are not density sensitive.
 Sorry.....
 Larry

 Larry,
 I disagree, there is a degree of self adjustment when crusing. There will
 obviously be a POWER loss as I'm sure you are aware. There are limits,
 because the diaphragm is frequently over sized so the slide will respond
 quickly, many sudden throttle openings, (like driving in traffic), will
 show rich on the plugs. Steady state crusing will lean after you reach
 steady state. With respect to aircraft, the carbs will work better than
 the
 motorcycle use since throttle openings don't change very quickly. For
 leaning that is

 Bill Jepson

 Thanks Bill, Larry, Matt & Vlad.
 There certainly are some interesting points, food for thought. Not as
 simple
 as I first thought.
 Never heard about lowering the jet instead of raising the needle Matt, my
 initial thoughts are that it may raise some sealing issues as the fuel
 goes
 through the jet - probably some O-rings involved. My idea of raising the
 needle may well need some O-rings as well
 I guess I will have to keep thinking.
 George (down under)

 Bill,
 you are correct in there is some degree of self adjusting, being a rung up
 the ladder from the typical booster venturi carb design.
 hot wire mass air is just further up the ladder.
 Larry

 Larry, Paul, and group,
 I think there are distinct ways to go on the Rotary. Simple: Carburetor
 induction and simple ignition, even coil and points will work. Moderate
 technology: Keep as many of the systems mechanical as possible. Bendix or
 airflow technology mechanical injection. Proven reliable
 electronicignition.
 Lastly full modern system: EMS or at leastfull electronicFI. I do agree
 withPaul that the modern MAF sensor is the way to go. These are very
 reliable devices and are not as pulse sensitive as the map sensor. For the
 rotary the EMS should be capable of being a "single lever" system with
 complete altitude compensation but for best results LOP operation should
 be
 possible.

 The modern system is where we have been headed, with some diversions. The
 rotary really begs for LOP operation to improve BSFC. The real problem
 that
 we have is that often people expect a system to be "bolt on" and that is a
 reasonable thing to want. The problem is that there are so may variables
 on
 amateur-built aircraft that it is almost impossible for an EMS to be
 programmed properly "out of the box". I read a very interesting article
 written by one of the recent Corvette engineers about all-electronic
 engine
 management systems. His comment was that to make one work (an EMS) took
 every bit as much tuning as a carburetor and mechanical ignition system,
 and
 sometimes more. It was a very honest evaluation, with the insight of a
 manufacturer to back it up. The comment he made was that every time you
 change induction, exhaust orengine internals a new complete engine map has
 to be made. The system will get the engine close to begin with and is
 somewhat self adjusting but fine tuning needs to be done for the
 particular
 combination of induction exhaust and engine timing. (cams and valves in a
 piston engine, porting and compression in the rotary)

 My point is that the
 guys that buy Tracy's system shouldn't be supprised that some tuning
 skills
 will be needed and the tuning will take some time. This is going to be
 true
 OF ANY SYSTEM from the simplest to the most complex. An EMS gives you more
 tools, and a degree of self-adjustment but you will still need to know
 what
 you are doing, there is no "silver bullet" system. When Paul was working
 on
 the dyno He didn't have the time, (read $$$), to tune Tracy's system and
 changed over and ran a carb system that the Mazdatrix had already spent
 the
 time tuning. A wise choice considering the cost of Dyno time. It seems
 like
 we cycle through the desire to keep everything a simple as possible to a
 full EMS and back. Any system used will take time to get exactly right.
 For
 what it's worth.
 Bill Jepson


 Paul,

 I apologize if my reply is hashed up..  I haven't got gmail fixed yet,
 but can't resist replying..  :)

 Not arguing with Bill..  I agree with his points in general.  But:

 The airplane operating requirements are relatively simple compared to
 that of a performance car like a Corvette.  In the Corvette, they want
 good throttle response at all RPM, and good fuel economy with very
 minimal driver involvement - one lever.  On the other hand, the
 airplane really has only a couple of requirements..  It can't quit.
 It can't burn too much fuel in cruise.  It has to make the peak
 horsepower afforded by the mechanical limits of the engine.  That's
 not too bad by comparison.  The airplane engine doesn't have to idle
 all that well as long as it doesn't actually quit.  It can have a
 separate lever for controlling power vs. economy.  All of this makes
 the tunability of the airplane easier to accomplish by comparison.

 As far as running the engine on the dyno, I think that was a p-port,
 and it was being run with the manifold pressure tap located at the
 wrong place on the engine for good readings.  It would be interesting
 to hop on the dyno with the mp tap installed in the housing and see
 how the tuning goes.


 Regards,

 Matt-

 Looks fixed to me. This looks fine.

 Paul Lamar


Wonderful response Bill. I would add that the choice between carb, mech fi,
efi, distributor, dis, etc boils down to not only simplicity but also cost.
This wouldn't be the case in the certified market but since we don't have to
jump hops for the FAA, we can choose our options based on more than just a
certificate. With regards to fuel delivery, it seems like the only two cost
effective options are the Holley and custom efi (555, Tracy's, Megasquirt.)
If someone could find a better carb in terms of function and cost, that
would be cool but at this point that seems very unlikely. Mech fi would be a
very good feature if it wasn't SO expensive. For $2900 I could buy a Motec
(read $$$) and still have money left for dyno tuning. While custom efi would
be the holy grail of performance and flexibility, how many people really
need it? The turbocharged and the aerobatic (are there any using Mazda's?)
could genuinely use them, for everyone else, seems unlikely.
Vlad
--


My problem with electronic FI is in the systems support..  Requires
independent, redundant power (dual alternators), and high pressure
fuel.  Not insurmountable by any means, but I'm not convinced the
payoff is worth it for what I want to be flying.


Matt-