efi555

[David Doddek]

>Darrell wrote:

>The hardware approach doesn't bother me, since, as Steve Ciarcia
>(Circuit Cellar Ink founder) says, "solder is my favorite
>programming language".  I am, however, a reasonable HC11
>programmer, but a complete fuel injection system is a major
>undertaking.  GM spends billions on R+D for their systems,
>with hundreds of programmers and engineers, along with all the
>necessary toys to test it along the way.  I'm talking about
>spending a few hundred on my daily driver and still being able to
>drive it to work every day during the development cycle...
>
>Regards
>dn
>
I would not say that a EFI system using a micro is that hard.  When knowing
nothing about EFI I designed a system using an 8085 and all descrete
hardware timers.  This project was done in only one semester in college and
worked well.  I now work for Caterpillar and like the auto companies, yes it
does take a while to develop an EFI system.  The moral is the big companies
take time to develop a system that is sold to the public and has to be
warrantied.  When you develop one for yourself there are a lot of areas that
you do not have to address, like reducing cost to the abosolute minimum and
passing corporate fuel econemy and emissions.  My second design of a system
was done, hardware and software in two weeks.  And it is still on my car.
As a matter of fact, I am currently in the process of making it for sale to
the public.  I have also made a analog system like the one being discussed
with the 555.  It used op amps and had a map sensor and fired one injection
per ignition event.  It worked well and it was the basis for the program
model for my current micro EFI system.  The one problem with an analog
system is that there is a large change in volumetric effeciency at low rpm
causing a rich mixture at idle in gear (automatic) and lean at low speed
cruse (30 mph)  However, something like this is not a concern on a race
engine that spends a lot of time at wide open throttle.  This is probably
why the race engine that the gentleman at superchips ran well.  An analog
system is possible and even possible to add a VE offset by using a couple of
a to d converters, an eprom and a d to a converter added into the main
voltage signal as an offset.  The inputs would be the map or maf signal and
the rpm from a frequency to voltage converter and the output would be the
data signal from the eprom through the d to a.  The rev limiter could even
be added by using a comparitor on the analog signal from the freq to voltage
converter.  You can do almost anything you want if you try hard enough.

Just a few silver pieces worth

David J. Doddek                                          |pantera at dris.com
Owner SGD Electronics & Development Engr for Caterpillar |h 309 685-7965
Formula SAE Team Sidewinder 94-95                        |w 309 578-2931
89 T-bird SC,  69 Fairlane w/SGD EFI                     |fx 217 428-4686
74 Pantera w/Electromitive Tec-II Twin turbos and Nitros |
Hey, If you are going to go fast, go REEEAAL FAST.       |