Injectors

[Frederic Breitwieser]

> What computer could I use for multiple(dual) port injector setup like
> that?

Well, I wouldn't want to design or build a system based on one or two
big-ass 100lb injectors.  If one gets stuck closed, you'd lose 1/2
your fuel and lean out.  Underboost, you'd detonate something fierce. 
If the reverse happened, where one injector got stuck open, you'd have
a flood, possibly a fire if the engine even runs at all.

This is one of the things I do like about multiple injectors, spread
around the intake runners, i.e. one injector per cylinder.  Fire 'em
sequentially, batch, a combination of the two, whatever, however if
one injector goes bad, on a V8 engine you could in theory limp home
with crappy performance.  But, you more than likely could get home.

Also, if you calculated out that you need two (see dual above) 100lb
injectors, that's 200lbs worth of injector performance at an 80% duty
cycle, divided by "banks" or "cylinders" depending how you want to
fire them, and you have smaller, less costly injectors.

An 18lb injector is cheaper than a 36lb injector which is cheaper than
a 100lb injector, typically, assuming the same vendor/manufacturer.

And of course, if you test them and determine the approximate flow,
you can get junkyard injectors for practically nothing, and put
together a nearly matched set.

> which the best most economical system I could use for this setup is!

The least aggrevating method of EFI for your needs based on what we
discussed would be the Electromotive Unit.  Buy the unit "naked" and
get all the GM sensors, injectors, etc, from the local you-pull-it
junkyard and wire it up.  Cut the wires long to all the
sensors/injectors so you have wires to play with as well as the proper
connectors.  Makes life easy down the road.

> can find an economical dual injector/cyl computer, that is...

Well, if you want dual injectors per cylinder, lets talk about this
:)  My 849HP Buick V6 ran three injectors per cylinder... all junkyard
injectors.

Stage I - managed by the Haltach ECM.
Stage II - logical "and" between the Pulsewidth of Stage I and the
boost pressure.  Meaning, that  the Stage II injectors don't fire
unless the same injector in Stage I fires "AND" the boost is over
9-10lbs of pressure.
Stage III - local "and" between the Pulsewidth of Stage I and the
boost pressure (higher), meaning that the Stage III injectors
(Isopropol/distilled water mixture) doesn't fire unless the same
injector in Stage I fires "AND" the boost was over 15lbs of pressure.

We did this using mosfets and op-amps, probably violating most of the
"rules" associated with electronics engineering, however it worked. 
LM324's are a generic op-amp and we used it to measure the boost in
the plenum, which fed an "ordinary" cmos buffer gate which then fed a
CMOS AND gate, which the other leg of said AND gate was fed by a
2n2222 transistor attached to the injector fire lead on the injector. 
wasn't all that complex, though being an analog/digital mix with the
programmable Haltach unit thinking something else was happening,
adjusting this setup was an absolute nasty bitch.  However, 849 HP out
of a Buick V6 with three injectors per cylinder is nothing to laugh
at.  It worked,  it worked well, and I should grab my notebook from
the shop and post some more of the details in the wiring.

Though, if I can do it, so can you.  Just because I used the Haltach
unit, doesn't mean you're locked into it.  The key is controlling the
maps in the ECM, whichever one you choose, to ensure that over a
certain boost level, when stage II and stage III kicks in, the tables
for injector pulsewidth LEVEL OFF, thus not increasing the time the
injectors are open.  As stage two started firing... performance dipped
because the mixture was slightly rich, until the RPMs and boost kept
going up, in which case it leveled off.  This indicates to me that we
didn't have the threshold just right, and some of the pulsewidth
settings in the Haltach might also have been off.  Stage III wasn't a
problem as its isopropol, and it cooled off the cylinders a bit yet
still burned.

It was a mess.  Two fuel tanks (one gas, one alky/water) and three
in-tank fuel pumps.  Two in the gas, one in the alky, all wired on for
constant pressure, which varied at the rails between 45-50 depending
on the engine RPMs and load.  More load, less pressure, as the fuel(s)
were disappearing faster, and stock pumps are... well... mediocre.

If you can, use Ford F150 pumps from the 89-93 model years... they are
external, don't seemed to be bothered by isopropol, and did I say
external and easily replacible? <G>.

Hope that helped.


-- 

Frederic Breitwieser
Bridgeport CT 06606

1993 Supercharged Lincoln Continental
1989 HWMMV w/turbocharged 500cid Caddy
1975 Dodge D200 Club Cab soon to have 431 stroker + turbos
2000 (I hope) Buick GTP (Mid-Engined Sports Car)