[Diy_efi] ION sensing question

[Brian Michalk]

Oh, I would dearly love to cobble up a DIY ION system.  I studied a lot of
Garfields posts, and may have enough bits to start a working thought model.
Before we get into analysis, we need to be able to collect the data.

**If I were to have it my way**, I would want it to be some sort of module
that I could put inline on the spark plug wire.  Don't really know if that's
possible though.  If not, should it be a coil system, or CD system?  I've
heard of different schemes of constantly biasing the voltage across the
plug, to more advanced schemes.

 Brian Michalk  <http://www.michalk.com>
Life is what you make of it ... never wish you had done something.
Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
musician, home-brewer, entrepreneur and mostly single


> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of Bevan Weiss
> Sent: Saturday, June 14, 2003 12:02 AM
> To: List for general do-it-yourself EFI talk
> Subject: Re: [Diy_efi] ION sensing question
>
>
>
> It's not quite as easy to use ION sensing to determine the AFR of
> the intake
> mixture.
> In a perfect combustion you will get H20 and C02... and this
> would be formed
> instantaneously, hence there would actually be no ION's to sense.
>  It's the
> intermediate steps and incomplete transformations that actually allow the
> ION sense technique to work.
> When the combustion begins, oxygen is turned in ozone, and free
> oxygen atoms
> (O3(2-) and O(2-))
> this then allows the remainder of the process to take place...
> The long hydrocarbons get broken down into slightly smaller hydrocarbons
> (perhaps ionic compounds) and water, as well as some CO2 and
> likely some CO.
> The process continues to get refined down until the end product is very
> close to complete combustion...
> CO2 and H2O, with trace hydrocarbons, carbon monoxide, ozone etc.
>
> Detecting the peak pressure is quite easy, because it's the point with the
> greatest ION concentration and hence the highest sense current.
> Misfire is
> quite easy to detect because it will have a very characteristic pressure
> curve, and will have a very low ION concentration overall.  Knock is only
> when the peak pressure point occurs before it's desired, the same
> is true of
> all detonation effects.
>
> To detect the mixture you would really have to do a huge number of
> calculations...
> The only real way I can think of doing it is via a trial and error method.
> Just change the fuel/air ratio either up or down, and see whether
> it changes
> the peak pressure at all.  Making sure that the timing is correct, so that
> the peak pressure point occurs where desired.
> If the peak pressure decreases then you should probably start to
> go back in
> the other direction.
>
>
> ----- Original Message -----
> From: "peterw" <peterw at waybeat.com.au>
> To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
> Sent: Saturday, June 14, 2003 4:14 PM
> Subject: [Diy_efi] ION sensing question
>
>
> > As I understand it ION sensing ignition systems can be used to
> determine,
> > combustion pressure, knock, misfire etc and these ignition systems are
> used
> > to adjust advance on a cycle by cycle basis.
> >
> > Does anyone know if ION sensing can be used to determine mixture ? If so
> > anyone point me to a relevant web link or other literature. My
> attempsts a
> > web serach turned up lots of references to either ignition systems or
> other
> > chemical exotica. Couldn't find any refrence to fuel mixture
> determination.
> >
> > Thanks
> > Peter
>
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