Second ION Report

[garfield at pilgrimhouse.com]

Hey maties.

I wasn't really planning on doing this right now, but the recent thread
on CDI spark duration vrs. inductive makes the "timing", if you'll
forgive the pun, too perfect to pass up. So for this report, just some
short quotes about ION's placement of it's "measurement windows" before
and after the spark, to catch bad boy events.

Again, pretty much all this is from #4,648,367, so I'll just say
col/line numbers. And please yous guys that know more about this spark
stuff from an ICE standpoint, could you pay attention to the distinction
they make between "pre-ignition" vrs. "knock" and let the rest of us
more benighted souls like me, know if this is standard terminology? TIA.

Now the quotes: [stuff in square brackets are my interjections]

(col. 5, line 42):
  "The time interval represented by the [measurement] windows may be
represented by a pre-determined crankshaft angle range both before and
after ignition. This range is defined by an angular position in degrees
in relation to TDC of the appropriate piston. Pre-ignition can thus
occur from 90deg before TDC to immediately before, i.e. a degree or two,
ignition [spark] voltage generation. The end of the pre-ignition window
is calculated by the microcomputer in unit 6 [the ECM] on the basis of
the calculated ignition time. In order that reliable detection of the
ion current can occur also for relatively high engine rpm, e.g. 6000rpm,
the pre-ignition window should cover at least 5deg within the range from
90deg BTDC to the postion of the crankshaft given above, immediately
before ignition voltage generation.
  "Knocking may be detected in a measurement window which begins as soon
as the spark is extinguished and which terminates at the latest by 50deg
ATDC. The window should cover at least 5deg [I believe this is a typo,
and they mean "at least 5deg within", and with capacitive systems it
should begin at, piston TDC for high rpm engines also, due to the very
short spark duration in the capacitive system."

Just as a side-comment, consider the generosity of this team of patent
authors, in explaining/discussing something in NO way required (quite
the contrary) for the protection of Saab's intellectual property. Even
in the process of "protecting" ideas, they are sharing far more than
they need to for mere protection purposes. Another reason why I find
these Saab patents headNshoulders above the rest. They're not stingy.

Anyway, think about them "windows" maties, and let's see if anyone has
any enlightening comments on them, and also on Saab's discussion of
"pre-ignition" and "knock".

Gar