REFLECTOR: Carburated Auto engine

Brian Michalk michalk at awpi.com
Tue Nov 23 13:17:11 CST 2004


Same value system here.

I put an Autronic on the Franklin.  And since I'm paranoid, I came up with
my own backup system.  Two injectors per cylinder.  The backup system runs
on a small SLA battery about the size of my fist.

According to my math, as long as the system is steady state, it will run the
engine for a couple hundred hours.
The backup fuel injection is constant flow, set by a needle valve.  Normally
the only power consumed is running the CPU (10mA at 20 MHz), and the sensors
(less than 8mA).  When the parameters change, the stepper motor is turned on
to re-adjust the valve.

There's no off switch.  The CPU in quiescent mode consumes about 15 uA
(20KHz).  That's .000015 amps at 3.3 volts DC.  The SLA battery is charged
from the airplane whenever the main Autronic EFI switch is on.

The CPU when running at 20KHz occasionally (several times a second) turns on
the sensor to check if the crank is turning.  If it is, and the main EFI
power bus is off, then it goes into active mode and assumes the backup
functions.

I have an overhead switch to turn on/off the main injector power in case of
emergency, or to test the system.

Of course the magneto is my ignition backup.
  -----Original Message-----
  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of NMFlyer1 at aol.com
  Sent: Tuesday, November 23, 2004 9:20 AM
  To: reflector at tvbf.org
  Subject: Re: REFLECTOR: Carburated Auto engine


  I had the same options when I designed my V-6 powerplant.  There are
plenty of computer programs (specially for the LT1) that tuning and
monitoring the EFI system are relatively easy. My sole concern of the EFI
system is the main processor.

   Most modern ECM's do have a "limp home mode".... that many don't
completely understand. The "limp home mode" only works if the system has
malfunctions/failures in the sensors.  IT DOES NOT HAVE A BACKUP IF THE ECM
ITSELF FAILS!!
  Since I have had 3 seperate computer failures, on 3 different types of
automobiles, all without warning. That was unacceptable.

  There is no doubt that a computerized EFI would be the most efficient. It
was just my choice not to trust the processor.

  By far, the least efficient would be the carb.  But; they are the good ole
technology.

  I chose the multi port Airflow Performance system for my own application,
but I believe the Ellison Throttle body is a good choice too.

  All the best,    Kurt
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