[Diy_efi] Ion Sensing project

[Marc Reibel]

On Thu, 4 Jul 2002, Garfield Willis wrote:

> On Thu, 4 Jul 2002 15:14:43 +0300 (EET DST), Ville Vartiovaara
> <vvartiov at cc.hut.fi> wrote:
>
> >But for ion sensing it's important that:
> >- The spark decays fast (no multispark or similar)
>
> In addition to the above, in your other recent post, you also remark
> about the CDI systems being faster than the coil/inductive spark
> systems. But you've said you have a conventional dizzy/coil arrangement.
> How are these two facts reconciled?
>
> It would seem your standard inductive IGN violates this 'fast decay'
> criterion. Unless you're overtly terminating the HV earlier than just
> letting the coil decay normally. Have you actually *measured* the decay
> time till the IGN pulse is passed the threshold of obscuring the ion
> current. I grant you, you have a spark gap in the dizzy to help you, but
> unless you have a very lossy coil, your spark durations at the plug are
> still going to be WAY longer than any CDI single-spark system.
>
> Just how clear and unobstructed a window do you really think you have to
> the post-ignition ionization period?
>
> Gar

Hi,

the problem with standart inductive ignition is the dwell
time of the coil, where the magnetic field build's up. In a
CDI you load a capacitor and not a coil, wich is way faster.
(not because it is capacitor, but because it gets loaded by
400V, not 12V lik ethe coil)
The standart inductive ignition gets the high primary
voltage by opening the current-path with the braker. The
magnetic field collapses and produces a high induction
voltage wich is then transformed to HV.
On the CDI you directly put 400 V to the primary winding, so
you have less loading time + no time needed to collapse
the magnetic field -> faster ignition.

Hope this get's clear in spite of my bad english ;)

Marc
-- 
Marc Reibel <marc at reibel-web.de> <http://www.reibel-web.de>
PGP Key: 0xBC41A832/B4BB 179B 38B1 6C65 31FA B51C DBB6 A50A
ICQ: 42168505



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