Bench racing ecms Even if ya hate 101 please read

[garfield at pilgrimhouse.com]

On Mon, 15 Jun 1998 17:16:51 -0400, "Bruce Plecan" <nacelp at bright.net>
wrote:

>any thoughts comments appreciated.

>A rpm signal generator, but have to work out an interface to module
>     is a transformer necessary?.  Ya think just a 1.2v DC pulse would
>    fire the module?.  Use a monstable 555 for the 1.2v, and then
>    an adjustable astable for rpm?

In the off chance I could help, I'm puzzled; yes, 1.2V pulse is fine to
trigger a GM module, but your last question has me puzzled. I presume
you're tryna mimic a dizzy/crank sensor feeding the ECU & module, so
WHERE's the 1.2VDC pulse coming from? Presumably from your "rpm
generator"? Yes? Then no I don't think you'll need anything more than
that for the module, but the ECM's another story. Usually, the mag
pickup goes to the module, and an ECM compatible IGN signal is derived
from the module to signal the ECM. This I presume was the way things
"began" at the "electronic IGN big bang", cuz they wanted the IGN system
to be able to live on, in spite of the death of the ECM. Later, that was
just a fond farewell, but anyway, normally the mag dizzy/crank sensor
for the IGN goes to the module, and THEN back to the ECM.

IF you're gonna get into the ECM's that expect both crank AND cam
signals, then we'll have to reconnoiter again (not hard, just more), but
for your present safari, yes, the falling edge of a 1.2VDC pulse will
fire a GM module, and the GM module can then be used to produce the REF
waveform back to the ECM (assuming still we're in GM-land). The GM ECM's
appear to expect to take over IGN timing at about 300-600rpm (depending
on #ofCyls), and take this REF signal as input for them to drive out to
the module, their adv-timing corrected result to the signal EST on the
IGN module, after raising BYPASS, so IF youNeye are still on the same
page, this should all work fine.

>Was going to use pots for MAP/TPS/Coolant/IAT.

This is fine for Coolant/IAT, but for MAP & TPS, to really prove you're
really able to handle transients (I know, this come's later; just
offering some "future thot"), you could/should have a mechanical arm
connected to a real TPS, and a vacuum pump connected to a real MAP. I
have "extras" of both, just lemme know. I ALSO got an extra for this
"hand-held vacuum pump" if you should want one later. Only thing, I GOT
the extra by getting a better pump that models both vacuum AND
boost/pressure, from them MituVac guys. They're ALL really pretty cheap,
y'all, but get their latest one that provides BOOST and VAC simulation.
But, Dr. Pelican, if you wanna play with NA eXperiments at first, lemme
know and I'll get you the pump, gratis cum grano salis.

BUT, yes, for static testing, pots will do just fino.

>12v lawn tractor battery, and circuit breakers.

Well, when the battery charger and the weight becomes a pain, you oughta
consider a surplus PC computer power supply which has both +- 12V and
+-5V, and for most of what you wanna do, would supply plenty of current
without the obnoxious presence of a lead-acid battery and charger.
Again, I got some big extra's if you wanna avail yerself of same. My
pleasure.

P.S. As lame as I may be concerning ECM/ECU/computerized engine
management things, I think this "bench ECM racing thang" is a really
cool idea! If it's perfected, it could lead to diy_efi guys building up
their stuff on the bench and fairly completely being able to test it
before putting it on the DUT ('device under test', in my trade; the REAL
engine). THAT can't hep but be a good thang, Dr. Pelican!, not to
mention the fact that it's a cool idear.

Gar