> Perry,
     >
     > Do you have a turbocharged engine or NA?
     >
     > Doug Fir

    It's stock 1986 NA.
    In the early days (1999) I was worried about the EFI not being a
    redundant system, but it's reliability is now proven (it was "proven"
    anyway in car use). Redundancy is only needed for failure prone systems,
    such as magnetos.
    The only redundancy I have is a dual battery system, independently
    selectable but I always run "both". Two sealed r-g lead-acid batteries.
    I've never had a battery failure either, I replaced the originals after
    5 years, running on the second set now.

    Perry

    I also might add, Perry is a very talented professional electronic
    engineer so EFI holds no mysteries for him.

    Now on the other hand (correct me if I am wrong Perry) he still has
    not got it to lean the engine manually :)

    I still think you need to try a pot in the mass airflow sensor
    circuit Perry.
    --
    Paul Lamar ...No rotor no motor.



I've designed avionics since 1980, mostly CRT displays and now LCD HUDs.
Some digital, some software, but mostly analog and switching power
supplies. EFI is not mysterious, however I have not dug into the
internals of the Mazda computer. I just use it as is. I doubt there is
any way to get schematics and source code from Mazda.

Sometimes I commute to work by airplane and park at a guy's house at
UAO. He is impressed that I just hop in, turn the switch, and takeoff,
as if it were a car.

For leaning, what I did was build a variable gain amplifier. The airflow
sensor signal is intercepted and routed to a switch. With the switch in
one position it sends the AFS signal to the ECU normally. In the other
position it routes it to the variable gain amplifier and that output
goes ot the ECU. For mixture I monitor the voltage on the O2 sensor. It
does work, I used it on the round-trip to Kansas summer 2006. Being
conservative, I made the adjustment range too narrow. I need to take it
back out of the cockpit and make a slight adjustment to fix that.

Perry

Perry,
Since you are in the know about electronics, I was wondering why you
made that statement::
Quote from above: "Redundancy is only needed for failure prone systems,
such as magnetos" .

I always thought that magnetos are pretty 'safe', that is to say they
display high reliability.
Now you say magnetos are "failure prone."
Could you elaborate on that, please. Do I have to change my thinking
about them?
What is going wrong with magnetos? What component, and how do they fail?
Just wondering.

Regards
Rolf

Reliability relative to other systems.

I'm not that knowledgeable or experienced with magnetos. Back when I was
flying rentals in the early 90s one was bad on the mag check and the
engine nearly died. I taxied back to the FBO and got a different
airplane. In a conventional light airplane that is the only system that
is generally made redundant, so it must be considered "higher risk".

A lot of homebuilts are now running a mag on one side and electronic
ignition on the other, but that may not be so much for reliability
reasons as for better economy and starting.

I previously said my only redundant system was batteries. I forgot I
also have two high pressure fuel pumps. I always run both in flight,
because the engine will shut down within seconds with no fuel pump. In
fact that is how I always shut down the engine, and it pressurizes the
fuel rails between flights. I've also never had a fuel pump fail yet either.

Perry

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