And for our Next Trick ... How 'bout a diyTrionic?

[Robert Harris]

According to my Heywood and others, knock is a physical phenomena that is
accompanied by acoustical noise, a high intensity optical flash, and a sharp
increase in ionization.

The gasses present both before and after ignition are essentially insulators
( that's why it takes 1000's of volts to fire the frigging plug ) and are
relatively non conductive.  Placing a low voltage on the plug - less than
needed to overcome the gas resistance - will result in little current flow.
IF an IONIZATION EVENT occurs, the conductance of the gasses will radically
increase, causing current to flow in the circuit.  This gross change in
current can be interpreted as a knock event - whether it is measured as
voltage or current makes little difference. Of course, I might be
misremembering basic electricity that says if you hold the voltage constant,
and the resistance decreases, current flow increases.  They might have
changes the laws of physics lately to be more fair to the lesser capable
electrons.

Next, with proper sophistication, much more can be determined from analyzing
the effect of a low voltage signal applied across the spark gap and
measuring the signal after ignition.   These areas are of intense interest
to virtually every engine manufacturer or racer.  This includes as I
understand it - cylinder pressure, fuel air mixtures, etc. The use of this
data can result in significant advantages and as such is more closely
guarded than Bill Clintons Bimbo phone list.

For a simple DIY, determining the fact that an IONIZATION event has occurred
suffices. This event of sharp increase in conductivity changes the current
flow at the low voltage on the plug significantly.  It is totally incapable
of rendering most of the additional data that a wazoo guru could extract,
but for those of us trying to get reliable knock detection on an engine that
was never fitted with an acoustic detector or so radically modified that the
fussy little shit no longer functions properly, being able to detect knock
is a MAJOR ADVANCE.

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.

> What can I say - this man obviously understands the principles of
> ion CURRENT
> measurement perfectly well - Bob, why don't you head the
> development team as you
> are such an expert!!!!