OEM algorithms (DSM)

[Jonathan R. Lusky]

Jim Pieronek writes:
> 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)
 
Been there, done that.  Although our algorithm was slightly different,
we got it driving OK, tune the ranges we'd see on the FTP on a road-load
chassis dyno, then fine tuned the rest on the road and didn't touch the
ranges we had tuned for the FTP (we werent very concerned with
driveability, we were VERY concerned with emissions).  

> 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!

How did yall tune EFI before UEGO's???  I know the box you are talking
about, we had one too.  Never did figure out what the thumbwheels did
or how to make the prom burner work, and GM wouldn't give us any docs. 

> 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.
 
City driving too...  spent a lot of time idling on the FTP.  Also cold
start and hot starts.

> 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.

I agree...  most existing aftermarket boxes are very simple compared to
OEM controller--too simple IMHO, which is why this project has such
great potential :)

-- 
Jonathan R. Lusky                        lusky at knuth.mtsu.edu
http://frank.mtsu.edu:8001/~lusky/          (615) 726-8700
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68 Camaro Convertible - 350 / TH350  \_/ 80 Toyota Celica - 20R / 5spd