Intake Runner Length
Van Setten, Tim (AZ75)
Tim.Van.Setten at CAS.honeywell.com
Mon Feb 1 21:59:38 GMT 1999
> >> What for ecm?.
> > We ended up conjuring our own. (Mainly by swiping circuits out of
> >every known ecm in the free world). We wanted a box with knobs on it
> that
> >controls the basic fuel curve. It's not a good idea to take a lap top
> out
> >into the sand dunes to change the fuel curve.
>
>
> Care to give any details about the ecm?.
>
The ecm started out using a 68HC11, but to make a very long story
short, we ended up making an analog system. The digital stuff is a
nightmare. You have to remember that this IS the most electrically noisy
environment around. Magnesium engines, steel frames, aluminum do-dads, high
RF fields from radios, lots of emi from magneto's, (to really screw up a
ecm, watch what a MSD 7AL2 multi-spark does using solid core wires), but the
topper is when some of these village-idiots use a garden tractor battery to
try starting a 13:1 compression motor!
Yes it can be done, and when we did this years ago, we were heading
for a box the size of a coffin to buffer, hold-up, condition, isolate, the
signals. The killer was using methanol and trying to convince the O2 sensor
to stay alive. When we went to a basic analog system, 99.99999% of the
problems went away. (No processor resets, endless loops, watch-dog timers,
etc..etc..).
Going to a speed-density system, (TPS and Tach), sequential-double
fire, we could use pot to trim overall curve, idle, mid, top end. Adding a
MAP gave us the additional curve for the boost correction fuel. I can't go
into schematics without giving up too many secrets, but I'll try to answer
questions. (Hope I answered some of your questions Bruce).
Tim.
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