FW: pulse width correction

[Zublin, Bryan (SD-MS)]

I have wondered about this myself.  I assume that this is done mainly to 
handle the low voltage when the engine is not running (12V vs. 14 V), and 
during starting (< 12 V).  Also, if the alternator dies, the voltage will 
slowly drop.

One could measure the change in injector flow rate at a fixed duty cycle 
with changes in voltage to come up with a correction curve.  I would guess 
that the "peak/hold" type of injector drivers would be less sensitive to 
voltage changes since they regulate the current to the injector, regardless 
of supply voltage.  Comments?

Bryan Zublin
bzublin at gi.com
 ----------
From: owner-diy_efi-outgoing
To: diy_efi
Subject: pulse width correction
Date: Monday, July 24, 1995 4:21PM

In perusing some sample EFI code, I noticed that a linear function was used 
to
adjust injector pulse width for changes in battery voltage.  The adjustments
appeared to range from 600 microseconds to 2000 microseconds as voltage went
from 16V to 6V.
Is it standard practice to use a linear function for this correction or is 
it
dependent only on the particular injector?  Does anyone know of a source of
information regarding ITO times and varying voltage can be found?

Any help would be appreciated.

Thanks,

Jeff