ION Project Papers & Info Sources

[H. J. Zivnak]

Right you are about the lack of analog black magic!  Take a look at Patent #
4,862,093.
That one transistor is there to turn-off the bias voltage during engine
cranking so the plug does not foul due to the charge across it.
I don't see any filtering at all.

Joe
-----Original Message-----
From: garfield at pilgrimhouse.com <garfield at pilgrimhouse.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, May 08, 1998 11:48 PM
Subject: Re: ION Project Papers & Info Sources


>On Fri, 08 May 1998 21:57:05 -0700, garfield at pilgrimhouse.com wrote:
>
>>On Fri, 08 May 98 19:37:02 -0700, Andrew Ghali <andrewg at netcom.com>
>>wrote:
>>>http://www.mecel.se/my_html/body_Ion_Sense.htm
>>>
>>>It mentions that Mecel has a patent issued in 1984 on ionization current
>>>measurement used in Saab's DI system.
>>
>>Excellent little blurb there.
>
>Just a couple follow-up comments and some NEWS. In looking at Mecel's
>page a lil more, I see that the DI system (which DOES include ion
>sensing for cylinder commutation) was intro'd in '87, which means this
>stuff IS 10 years old. The other thing to note is that although the
>patent was issued in '84 and deployed in '87, there is a real dearth of
>articles/papers until the mid-ninties. In larger corporate circles, this
>usually means there was a "ban" on publishing sensitive info until
>several years and cash cows could be harvested. This is a likely
>indication that Saab WAS INDEED tryna keep the stuff secret for quite a
>few years.
>
>Now the bit of news. You will note on the Mecel page that there's been a
>DI system in the 9000s since 87/88? Well, a buddy of mine, who manages a
>Saab parts dept. and whom I've been plying with questions since this all
>started, today came up with some notes and a warrantee unit from a '90
>Saab, and the lil board that does the Ion Detection stuff in those
>earlier models is readily viewable (unlike the later models, that are
>SERIOUSLY potted) if you remove the protective covers. On that lil board
>that stands up like a "module" SIP, the ONLY active parts are an LM-139
>Quad Comparator (SGS-Thomson variety with cerdip and -25 to +125degC
>rating, so them guys know what they're doin) and a lone transistor. A
>sprinkling of the usual diodes and passive discretes, of course, but the
>point IS, it ain't no special sauce or any analog black magic, cuz there
>ain't even no op amps, so if there IS any filtering it's of the lowliest
>kind, since there is no active filtering possible on this board. I
>traced the circuit out enough to know for sure this IS the module that
>does the ion detection, cuz two of them comparators directly drive the
>signals that say which cylinder is firing. This is EXTREMELY
>encouraging, cuz if we can understand this technology, the circuitry to
>implement it obviously is pretty dirt simple AND dirt cheap. As a result
>of this latest intel, I am even more confident that after digesting the
>available papers and summing up all our fractional wits, we're VERY
>likely to get a workable DIY implementation. ION is beginning to smile
>upon us, methinks. Maybe if we're nice to her, she's tell us her
>secrets. B)
>
>Gar
>