Creating a pulse for injector drivers

[Bruce Bowling]

> First off, good choice on a CPU.  They are cheap, avail in many, many case
> styles, and have eight A/D converters built in (you might learn some
> limitations as you folks tinker, but that's okay <G>).
> 
> >  creating the pulse sent to the injector drivers.  The trouble is with
> >  using an output compare to create the pulse.  An output compare can be
> 
> Driving a pulse driver can be as simple as an output transister (FET's are
> faster than Bipolar of course), however I'm thinking your question is pulse
> duration.

Check out the EFI332 www page - there is a group of people designing an efi
based on the 68332:

http://efi332.eng.ohio-state.edu

> 
> The duration can come from a pre-calculated "map" within your eeprom for each
> RPM range (500-1k, 1k-1.5k, etc) and your system then adjusts automatically,
> following the engine.  Another option is to monitor engine rotation so at
> certain points after the injection starts, the injector stops.  However this
> introduces mechanical items into the mix.
> 
> I'd go with the calculated map approach personally.  BTW, what do you need a
> compare for on the output?  Just curious, because I was under the impression
> that an injector is basically a coil that when energized, allows a
> predetermined amount of fuel into the cylinder based on the internal
> bore/valving assembly.
> 
> I am not a fuel injection guru by any means...
> 
> 
> 
> 
The equations for the speed-density method of EFI can be found at:

  http://efi332.eng.ohio-state.edu/grippo/equations.html

- Bruce


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                 Bruce A. Bowling
                 Staff Scientist
   Thomas Jefferson National Accelerator Facility
    12000 Jefferson Ave - Newport News, VA 23602
                 (804) 249-7240
bowling at cebaf.gov  http://devserve.cebaf.gov/~bowling
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