First ION Report & Short EGOR Update

[garfield at pilgrimhouse.com]

Hey Maties.

Been tryna get this done and out for almost a week now. Toooo busy.
Retirement can be very demanding, especially on the uptake.

First on EGOR, since that one is short. Am awaiting arrival of some
small bits of test equipment I promised I'd send Frank along with EGOR
to keep him company. Soon as that arrives, off he goes. Also, another
list member who has a dyno and an ECM O2 meter (around $6K) has kindly
offered to do some comparison runs with EGOR, so we'll probably send the
ole E'bean along there on it's return trip home from Frank's, assuming
all goes well with the NTK comparison.

Now about ION. As promised, here's an encapsulation of what I've found
from rummaging thru the patents so far. The purpose of these blurbs is
to try to keep everyone, that's interested in following along or
contributing, on roughly the same page and terminology. That way, when
anyone finds something germain, they don't have to start from the
beginning every time.

So on to the patents:

There are schemes presented for doing ion detect on EVERY kind of IGN
system, including dizzified, wasteFired, and obviously DI/coil-per-plug.
All the methods I see in the patents for applying ion detect to dizzies
requires HV diodes in one form or another (basically to remove the
dizzy's rotor/cap air gap from the circuit while measuring the
ionization current; they can do this because the spark polarity is
OPPOSITE the ionization measurement bias voltage). This is also true of
some of the implementations even for DI. Since these HV diodes currently
available are actually a stack of several/many junctions, they're not as
failure prone as one might think, but still, a design that does away
with ANY requirement for HV protection/diodes is a plus.

Such is the Saab design. Other patents where no HV diodes are required
either do something very similar to Saab, or else just simply reference
Saab's patent. There are so many trick things in that Saab design, that
I can't help but think the guy(s) that did that design was just dead
brilliant! It requires NO HV diodes. It uses Schottky diodes for their
low forward drop, to protect parts of the circuit, AND at the same time,
makes use of these same Schottky's low Vbr to implement the equivalent
of a transorb in the reverse direction! Poof, all with one diode. Very
clever. To detect ion current levels, instead of using a fixed reference
comparison level, it uses the OTHER ion detect circuit that's idle to
establish a comparator reference level for the one that IS active, and
visa versa. Amazing. In one case it uses a Schottky to also allow the
spark current to charge a capacitor to the voltage to be used to measure
the ionization current, sorta like pumping up a trickle charging
circuit, and then uses the Vbr of the SAME Schottky in the reverse
direction to limit the max level that the capacitor charges to! Lots of
cool tricks like this, that took some time to figure out, but were well
worth the effort. So much for circuit wizardry.

Instead of publishing what would essentially be a COPY of the patent
with values and explanation, instead, when ION is released, I'll be
posting a text discussion which references the numbered circuit elements
in the patent itself, like any good research paper would. The patents
are ready made drawings we can use for discussion, since the actual REAL
circuit is almost exactly the same. Also keeps within the spirit of
"research" follow-thru, in that you're implementing their stuff
essentially to study and improve if possible. NOT for commercial
exploitation. Here, I don't even have to worry about someone exploiting
my own work, like EGOR's "commercial no-no caveat". If you use ION for
commercial exploitation, you'll be in direct breach of Saab's patent.
Not my worry. Heh.

The other thing I wanted to pass along is the important "second order
effects" of applying this fixed DC voltage bias across the spark plug,
in order to detect/measure ion current. The very first Saab patent
(4,648,367, filed Dec '85, granted March '87, a DECADE ago!) speaks of
using 400V bias to measure ionization current. The NEXT patent
(4,862,093, filed Aug. '88, granted Aug. '89) right on it's heels and
only a year before it was first deployed in the field (well, three years
isn't much time in research circles, heh) mentions a "problem" with
leaving this bias on the plugs all the time, namely SOOT! Yes, soot.
Seems that as they played with the thang in the lab, they discovered
that this constant bias (can you say "static electricity"?) was
attracting the minute carbon particles in the exploded gas/air charge,
and depositing this on the plugs!! NOT good. Heh.

So the next patent "discloses" two new "inventive methods". One is that
the voltage of the bias is REDUCED to 80V. The other is that the bias is
NOT applied to the plugs until the engine is up and running, and the
plugs are cleaned thereby. Then the 80V is switched in to start the ion
detection process, and determine which of the two cylinders are firing,
and thereby providing "cam sensor" info and allowing fully sequential
IGN and EFI. It is further disclosed that while 80V is sufficient to
detect "normal" IGN explosions or not, 400V is much better for detecting
marginal and abnormal things like a "sooty" or fouled plug, or
pre-ignition, or detonation. Further, the observation is made that since
detonation is associated with warm engine conditions, that the 400V
measurement bias on the plugs may be applied, once the engine is warmed
up thoroughly and self-cleaning the plugs, and therefore isn't subject
to sooting up the plugs, as before. I think this last disclosure
indicates that the latter implementations of Saab's Ion Detection
circuitry ('93 and beyond, for which we have NO disclosure) switch
between NO bias, 80V bias just after startup to provide commutation, and
then once the engine is warm, switching to 400V bias to improve the
measurement accuracy of these ionization events, in order to detect
knock.

That's it. NO fancy filtering, except maybe inside the ECU when reading
the raw ION current signal via an A/D for knock detection, and
fire/misfire detection is done outside the ECU, simply with a blanking
window around the time the plug fires, followed by a simple
"self-referencing" comparison level (which I mentioned earlier) for
detecting fire/no-fire on the plug. After that, I believe the detection
voltage is raised to 400V, and the raw ionization signal is then scanned
directly by the ECU to look for any anomalies.

In my next installment/progress report, I'll mention the size of these
"detection" and "scanning" windows in crank degrees (quite interesting,
AND of interest to any ION afficianados who wanna put such scanning in
the knock detection algorithm of their custom ECU's), which is ALSO
disclosed in those Saab patents. I am completely convinced now that the
reason why Saab so far is the ONLY mfg. to deploy this technology isn't
because they've got the tech sown up with their patents, but simply
because they've done their homework, and are MILES ahead of the rest.

The other thing I am even MORE convinced is that there is NOTHING
standing in the way of us bloaks using/playing with/researching this
tech to our own benefit and the "advancement of the stateOdeOit"
sotaspeak. I hate to say it, but the circuitry for ION is indeed even
simpler than EGOR. I had SOOO hoped to upstage that rascal. Oh well. One
thing we CAN say is that EGOR is totally eclipsed by ION's "beauty and
simplicity", and even I can say that without prideNprejudice, since it's
really them SAAB guys that have given ION her beauty, not I. I am simply
the amanuensis. But a privilege to serve her that way, nonetheless!

Gar

P.S. Key SAAB patent number is 4,862,093. If you read carefully,
everything is there. You don't even need ME. Sniffle. But, if I can save
you some time by being your guide, I am happy to do so with circuit
commentaries, parts values, and explanations. Kinda like one of them
tour guides. B)...More to come; stay tuned.