PC's and EFI

[Raymond C Drouillard]

I think that what we are missin in this discussion is that nice little
piece of paper that comes before all of the projects that the "big guys"
do.  Yep, I'm talking about the DESIGN OBJECTIVES.

We have lots of smart people calling each other's ideas stupid, when
careful reading will uncover the fact that they all have different
hammers, and are trying to hit different nails.

I'll start out by laying out my design objectives (if I needed another
hobby, that is... ha ha)

1) Use all off-the-shelf products.  Don't design any custom circuitry
that is complex enough to need more than a rudimentary circuit board.  A
few power transisters (FETs, whatever) to power the injecters, some
op-amps to precondition the sensor inputs, etc.

2) Use standard PC hardware and software.  Don't require any fancy
interfacing or a whole pile of machine code.  If you can write the system
in BASIC, FORTRAN, or whatever you prefer, it'll be easier to continue to
develop the program so that it'll eventually be able to start with a
rudimentary map and learn what the engine needs.  If you decide to change
the cam a couple of years down the line, just run the engine through its
pases and the system will readjust itself.

3) Use standard "junkyard" automotive components.

The idea is to grab an old 386 or 486, add a game port or two, add a
sound card, breadboard a few op-amp circuits, and install it into a
running carburated car.  Once you are reading all of the inputs and have
come up with code that will drive the outputs, start replacing things. 
Solder together your breadboarded electronics.  Replace the fly weights
and vacuum advance with your timing output.  Replace the carb with a
throttle body.  Later, pull the injecters off the throttle body and put
some into the manifold.  All of that will be done without worrying about
how many wait states you need to interface the microprocesser to the
memory, how to hook an A/D converter to the microprocesser and how to
address it to the I/O lines, etc.

This obviously isn't a solution that will be mass-produced, but who
cares?  The person who comes up with it could make a little cash by
selling it as a kit.

Ray Drouillard, BSEE


On Thu, 19 Mar 1998 00:08:04 -0800 Sandy <sganz at wgn.net> writes:
>Everyone is getting a bit wound up on building something, I think it all
>depends on what you are trying to do. The 4.77Mhz pc will work, but I'm
pretty
>sure that you won't get SFI and lots of the extras that a more sutable
>processor will bring to the table. I'm very sure that if the goal is to
make it
>simple, just whip out a couple of 555 timers and some FET's and connect
a pot
>to the throttle and you will have a simple injector (or a PIC). If that
is what
>you want so be it, if you want to build something inexpesive, again,
looks for
>some processors that can do alot of the messy work, 8031's, 8051's,
80C535,
>68HC11's, these are all very nice starting points to building a nice
injector
>or ignition system without a lot of BS PC based hardware. Cheep
compilers,
>assemblers, debuggers, and related freeware readly available. These
processors
>are in hundreds of thousands of cars, so they must work. By the time you
fart
>around with a PC, the Operating system, floppies, and that crap, you
couldhave
>hardware that is a 10th of the size and won't die when you hit a pot
hole.
>Remember you could be out on a dark road and how nice it would be to see
>'General Protection Falt at address 0x12345'. The whole design,
electrical and
>physical of a pc is just wrong, end of story. If you want to get access
to you
>controller buy an old laptop, or better yet, get a windows CE machine, I
have a
>compaq that has the terminal emulator and a RS232 port and you now have
a pc
>interface. They can't give away the some of the CE machines, so the
price is
>low, runs on battery's and you can cram a large flash card to store your
data.
>Hey don't get me wrong, I would love to write my software in Delphi and
use a
>PC, but this would only end up as another one of the scrapped project
that has
>lots of wires soldered to the back of it with a label that says 'Wasted
Time'.
>
>Let the flames begin.
>
>Sandy
>UP LATE, CRANKY, and CAN'T FIND MY DAMM POINTY HAT...OOPS, ITS ON MY 
>HEAD. 
>

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