Coils for Ion

[garfield at pilgrimhouse.com]

On Wed, 3 Jun 1998 10:05:48 -0400, "Bruce Plecan" <nacelp at bright.net>
wrote:

>>VERY high frequency what-looks-like-noise fuzz on top of what
>>is usually refered to as the "arc line", the portion of the waveform
>>just after the HV spike has ignited the charge, if you look at it on a
>>scope, it will always look like it's a THICK line segment, suggesting
>>there's a small very high frequency component superimposed. That's
>>apparently the resonance of the plasma itself.

Actually, this gives me a chance to correct meself; that description of
the "arc line" portion is faulty. The "arc line" is the short flat
segment of the waveform just after the spark ARC occurs, not when the
mix explodes. It's an electrical phenom we're looking at, not a
combustion one. The plasma that's conducting is the plasma formed
between the electrodes, not the larger one formed by the explosion of
the charge. So if you're looking on a scope, it's the first lower
voltage segment, right after the HV peaks, and the spark plug goes off.
Sorry if my description confused anyone.

>The one thing I thought I brought to the dance was tune-up info., and
>here a dang EE teaches me about a scope pattern.  I will return to my seat
>in the corner and humbly lurk with my CSH on.

Uh huh. Fat chance of THAT happening. Hee. Actually, I'd bet on most
diagnostic scopes, you wouldn't SEE the fuzz, the line would just look
some more blurry than the rest of the waveform. Of necessity, diag
scopes really aren't built to look for stuff like this (really, why
bother). The place I first saw this "arc line" thickness was in a really
old book that Hewlett-Packard produced to go along with a special
purpose scope they made for analyzing stationary engines, which
consisted of a package of a bunch of scope plug-ins and sensors so you
could view vibration, cyl pressure, IGN all together, and vewy vewy
cawefuwwy, as Elmer Fudd would say.

Instead of buying all them parts, when I was a lowly poor student, I
snagged the book and the part no. for just the capacitive IGN probe,
which I paid $35 for in 1975. The receipt is the bookmarker for the
book! It's one of my treasures, the book that is B). They have scope
pictures of all kinds of things like what detonation looks like in terms
of both vibes and actual cyl pressure, what valve noise and piston slap
look like on the scope, etc. You CAN buy in-cylinder pressure
transducers now that incorporate sparkplug and pressure transducer, and
they are STILL expensive. This was over 20 yrs ago, when they were truly
SUPER expensive! I forget how much that one sensor was, but I DO
remember I couldn't afford it, let alone the rest of the package.

But see, that instrument was small (well, relative to a shop scope),
portable with lots of cords, plugins and sensors, and was VEWY VEWY
expensive. My point in mentioning all of this is that for most
automotive diagnosis, this kinda approach, with a fairly high frequency
scope, would be overkill and prohibitively expensive. But tryna find a
problem on an engine the size of a house is another ballgame entirely.

Think about it. I've been mildly wondering why that arc line was so
thickish for over 22 years, and just a few months ago whilst discussing
the ION project with this mate at work, he drops the answer on me. Some
times ya just gotta wait for the answer!

This makes me think in my retirement, I should try to scan some of those
pictures in. The book is soooo long outta print, I can't imagine Tek
minding, and they NEVER would come out on a xerox copier, too much
detail lost, but with some good big scans, putting them up on the web
might be REAL plausible, and a good way to preserve this bit of
archeological treasure. One of them pictures, and the paragraph or two
from the book, would really be a nice resource. Yeah, I oughta put that
on my to-do list.

Sooo much fun, so little time.

Gar