OEM algorithms (DSM)

[Jim Pieronek]

"Todd Day" writes:

[snip a bunch of interesting algorithm stuff]

 > 
 > P.S.  After wading through 12k of OEM code for a few months (and this was
 > 	code written in the late 80's on an 8bit micro), I just don't
 > 	see how a handful of people in their spare time could even
 > 	come close to the complex cases handled by a manufacturer
 > 	with years of experience.  I've also dumped an ECU (4k ROM) from
 > 	the early 80's that was much much simpler, and I don't even think
 > 	I'd ever think of every case covered by that simpler ECU.
 > -- 
 >

When I was at GM in the mid-80's we had two guys working on the ECM
code for the Quad 4 engine.  The methods that we used were identical
to what I've heard people describe in this group:

  instrument your system;
  repeat {
    drive it around for a while;
    take a stab at a better way;
  } until (out-of-time)

The nice thing about do-it-yourselfers is that out-of-time is never
true!  We had pretty crummy instrumentation, the most interesting of
which was a box mounted on top of the dash that could show four
user-selectable engine parameters.  There was no recording capability.
Those boxes were the cause of many rear-end collisions!

It was relatively easy to get an engine up and running.  It took a
little more effort to get good performance.  But what took up most of
our time was getting the thing to have both good performance and to be
able to pass the EPA dyno emissions test.  In that test, a dyno is
programmed to simulate some EPA employee's drive to work in
California.  I think it was 17 miles of highway and mountainous roads.

The other thing that we spent a great deal of time on was starting.
We had to be able to do a no-pedal start from -40F to 120F.  This was
quite tricky.

So I imagine that a lot of what you are seeing in that code are tweeks
to make it pass the dyno emissions test.  In a diy job, all you need
to do is pass the simple idle emissions test.  The other thing that
you need to do is keep your mix right so you don't roast your
converter, if you use one.  I think it's well within reason to expect
diy'ers to be able to do a pretty good job on a controller.

- Jim
===================================================================
J. V. Pieronek                            Phone: (505) 243-5822
M.I.T. Lincoln Laboratory                 FAX:   (505) 243-5823
Terminal Radar Development Facility       Internet: jvp at ll.mit.edu
Albuquerque, New Mexico