Re: ECM Availability

[Garfield Willis <garwillis@msn.com>]

On Mon, 21 Aug 2000 19:45:29 -0400, "Bruce Plecan" <nacelp@bright.net>
wrote:

>So you want the ecm running, with a limp home, and a redundant independent
>system?

Let's take the simplest scenario & setup. Spose we have an inactive
backup. It's not running; it's operationally outta the picture. Then
the primary ecm fails. Switch OFF the primary ecm and switch ON the
backup system (may or may not be an ecm). Fly the backup to a divert
point and fix the primary. The backup may be extremely simple, and
only provide 100% power, for example, so it's only there to get you
down safely for repairs to the primary. We actually have a number of
schemes for backup, including a way to run two ecms completely in
parallel, both active, but that would take some time to explain, and
isn't germain to the main issue, which is "how quickly/easily can you
obtain a replacement ecm". In either case, as soon as you know your
primary has failed, you want to get down and repair it so you are
ALWAYS flying with a backup ready.

>Jus trying to get this right

Sure no problem, I appreciate it; lots of variations possible.

>4 Cyl
>Forgot TBI or TPI?

Most of us will likely go with PI, since that's the way the engines we
use have their induction setup in the first place. But there is some
interest in TBI, since you could use a simpler TBI setup as a backup
on the PI system. But mostly for the purposes of our main interest, I
think we'd be gravitating towards PI for the primary.

>Use the MAP for altitude compensation,
>and then a "master overide" for fuel trim?

Actually, that brings up a main motivation for using the ecms that
have been hac'd, so slight tweeks to the code could be done to say
substitute a manual mix control for a temp sensor input, and have the
code handle the enrichment to cover both fuel trim and cold-start
enrichment, albeit both would be handled by the same manual
adjustment. This also because it's very likely that some will want to
run the ecm in OL *all* the time, since 100LL is an issue with O2
sensors still, and it'll be several years at the least before the
unleaded Avgas becomes widely available.

Gar


----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org