That would definitely be an elegant solution. It would still see a current draw of maybe 10 to 20 amps for the fuel pumps, ignition coils and EC-2, but that would be nowhere near the 100 or 100's of amps the starter pulls which is what brings the starter battery to its knees.

A thought -- there's no real reason to run both pumps during start-up, is there?

Finn

Bulent Aliev wrote:

David, I'm thinking more like a small 12V battery only for the avionics bus
protected by an isolator? So the starter won't pull it down, but the battery
will supply initial 12v to the computer. My starter even scrambles the EM2
display if it's on. I'm not so good with electricity, but many of you here
are .
Buly

On 1/18/05 12:26 AM, "David Carter" <dcarter@datarecall.net> wrote:

  

Having lurked on the Aeroelectric List for years, 'Lectric Bob & his Z
diagrams use a "Low Voltage" module (LVM) of some sort that turn on a "low
valtage light" when alternator fails and voltage drops below "min voltage to
charge a battery", something like 13.8v, with voltage regulator set for
something just over 14 v so battery gets charged for sure.

So, given that "data point", looks like it might be useful for us folks with
"computer dependent" engines, which need 9v (for this particular ECU), to
fabricate a second LVM (set for 9.1 or 9.3 v) that turns on a light - or
voice warning - to tell us "voltage too low to start" (i.e., below ECU
minimum voltage required to start).  I'd probably put the light close to
the starter switch.

David
----- Original Message -----
From: "Bulent Aliev" <atlasyts@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, January 17, 2005 10:24 PM
Subject: [FlyRotary] New discovery...


    

For some time I was so proud my engine would start right away. The last
      

time
    

on Friday night I started it few times and everything was fine. Came back
this morning and tried to start it again, no joy? For hours I tried
everything, plugs, coils injectors, everything was fine. Kept cranking,
fired once for a second and died again. Even starting spray didn't do it.
The last thing (lunch time) I measured the voltage while cranking and it
      

was
    

9V. Ahaaa! I remembered something about the computer not working below 9V.
I hooked the charger and went for a long lunch with the airport bums..Came
back in 3 hrs and BINGO! started right away many times.
So the moral of the story is (I think?). If you have enough power to crank
the engine, does not mean that it will start. The starter pulls down all
      

the
    

available juice and the computer takes a break. Any comments?
Buly
      

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