ION Current measurement - was "And for our Next Trick ... How 'bout a diyTrionic?"

[Tony Cooper]

garfield at pilgrimhouse.com wrote:

> On Wed, 6 May 1998 06:26:00 -0700, "Robert Harris"
> <bob at bobthecomputerguy.com> wrote:
>
> <Small Snip>
>
> >Sorry Mr. Cooper, if our silly ass understanding and plebeian purpose does
> >not allow us to truly dissect the entrails that your more obvious
> >sophistication and expectations does.
>
> Hey, lemme get real serious for a moment and suggest you two knock this
> off pronto. I dunno what personal things are detonating between the two
> of you, and it isn't my business, and you're entitled to not care for

> <Nuther snip>
> Gar

 STOP.... Ok, before we get into a REAL slagging match, please try to understand
the following.

I do NOT have any personal greivance/lovehate relationship with Bob. As a member
of this list I enjoy the different ideas that come and go as discussions. I am
quite happy to contribute my 2P's worth to all/any idea's. If a member of the
list asks a question, and I can help with an answer, I am more than willing to
assist. If an expert member of the list gives advice, I am more than willing to
listen and learn.

However, when a member of the list arrives on a thread and starts authoritivly
spouting supposed facts - especially facts that are blatantly incorrect, I am
sorry but I have to chirp up and put my 2p's worth in. Now this doesn't happen
much - in fact the only time I can really help the list is when it touches on a
subject that is really close to my heart.

Now - shall we put this bickering to bed and get on with the job in hand.

Here are my thoughts on ION Current measurement.

As far as I understand the SAAB system it works like this.

After the IONisation event has been started (An IONisation event being setting
fire to the mixture) the SAAB system floats a DC voltage across the plug gap.
There will be current flow which is directly proportional to the burn rate of the
mixture. A graph of current flow can be seen at this address :-

http://www.vehicular.isy.liu.se/Research/activity96/node5.html
(Gra

Using a high pass filter - (which has been tuned to the SAAB engine in question)
it filters out any high frequency noise in the Flame Front and Post flame parts
of the graph. If there is noise of a particular frequency present, then a
detonation event has occured. This is fed back to the ignition system, and the
ignition timing will be changed according to the algorithm used.

Now, for a particular engine the detonation frequency can be found easily (Just
make your engine detonate!!!) so the correct values for the filter can be
calculated - However, it gets somewhat tricky to build a system that will bolt on
to any engine and work because no 2 engines (different models that is) are the
same. The best way to get around this problem is to use some sort of intelligence
to move the filter frequency around, and also calibrate itself to the magnitude
that is allowable knock - (Bearing in mind that an engine runs best when it is
only just detonating). And guess what a DSP is built for doing this. The cost of
such a system should be around the 20 UK Pound mark.

Just to whet your appitite more - hows about this lot of goodies available.

Measurement of torque for each cylinder as the engine is running.
Measurement of mixture.
Ability to inform you on the state of your valves/rings/plugs etc etc

In can go on.......

Tony

--
Sent By Tony Cooper.
email: tony.cooper at virgin.net
Allow at least 10 working minutes for reply. ;)