Algorithm vs. fuel map

[Tony Bryant]

----- Original Message -----
From: "Santi Udomkesmalee" <scathontiphat at hotmail.com>
To: <diy_efi at diy-efi.org>
Sent: Friday, September 28, 2001 4:55 PM
Subject: Algorithm vs. fuel map
>
> So my question is regarding the calculation of proper pulsewidths by the
> ECM.  It is my understanding that a system like the Megasquirt uses
> algorithms which calculate on the fly the proper pulse width from the
needed
> inputs.  What sort of advantage does this have over useing a system which
> looks up the pulsewidth in a preprogramed fuel map.  It seems that in a
> sequential injection situation at high rpms, the processing power to
> continuously calculate the proper injection would get costly when
designing
> a system.  What are the draw backs of using a system with a pre-programed
3D
> fuel map.  I may be misunderstanding how these systems work though.  It
> seems to me that while a preprogramed map might take slightly longer to
> program, it would result in a cheaper and possibly more reliable system.
>

It always struck me that the algorithm technique is the "correct" way of
doing
things. It allows you to apply corrections (e.g. water temp, air temp) in
the most
appropriate ways. But the problem comes if you want to apply learned
information,
e.g. from an oxygen sensor. When all you have is a 3D map, you can just get
the
learning to twiddle the appropriate points in the map and you're done. With
an
algorithm system, you've got potentially alot of parameters to possibly
twiddle,
and no indication of which one could actually be wrong. The same thing
applies
to a human adjusting parameters.

Beside the IC engine is just a little too complex a beasty to full specify
with
algorithms.

The best way IMHO, is a hybrid system, where you have a 3D VE table (with
RPM & MAP/AFM inputs), and then apply modifiers, injector rates, etc
from there.





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