[Diy_efi] Ion Sensing project

[Ville Vartiovaara]

> > And CDI has shorter decay time than a plain coil, so..
> > And why shouldn't ion sensing be used to detect misfire and launch an
> > additional spark in such a case..?
> 
> If your going to be sensing, things at around/until, 12 ATDC what real good
> is another spark at 14d ATDC going to do?.    Isn't this just getting to be
> feature creep?.

Misfire detection doesn't have to be that late.. The system should first
(just after spark) detect if the flame term of the ion current signal is
missing, i.e. the signal doesn't start rising fast enough. That's a lot
before TDC, especially at misfire-prone light-to-medium load.

Actually, I think some implementation of this has been done.. Not sure, at
least it was discussed in some of the papers around.. It's much simpler
than the actual PPP estimation..

 
> > The problem with CDI is usually the ringing on the HV side after the
> > spark, which may corrupt the ion sensing process.. But this is just a
> > misfeature of the cap and coil and bad design..
> 
> Can you give a simple explaination why a CDI would have more ringing then a
> conventional setup?.   It would seem to me, that with a faster rise time,
> there would also be a faster decay.

Decay is definitely faster, but self-induction in the coil will charge the
capacitor a bit backwards if the control doesn't cut the path soon enough.
The effect is plain self-resonance of a LC circuit, and has a clear effect
when measured.. A plain coil (conventional layout with no capacitor to be 
recharged) has so minimal capacitance at the leads that ringing is 
neglible.



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