Knock Question

[Thor Johnson]

> Heywood while referring to the measurement of ionization, leaves the
> methodology to do so as an exercise for the student.  So what I am asking
> for help on is any references to how to measure the ionization - SAE
papers,
> Reference books not leaving it as an exercise for the student etc.
Circuit
> Ideas for modifying the ignition would work. One idea that springs to mind
> (I am absolutely positive it has been done before by someone!) is to use a
> separate spark plug in the exhaust as an ionization detector.

Do this & I think you should be able to get some results:

Take a sparkplug & tap a hole for it in your exhaust (make sure electrode is
in th stream).
You may want to file the electrodes to pointy things or might not.  I dunno.

If you put a high voltage across it (you shouldn't need enough to arc), and
measure the current, you should have something related to ionization in your
exhaust stream (more current for a given voltage = more ions.  w/o arcing, I
think you want to be in the somewhere in the 1-10uA ranges... I have no idea
of the volage required).

If you're sneaky enough (Jacob's or A/C Delco research), you can use the
real sparkplug as your sensor by monitoring the discharge cuve (& possibly
keeping a high, nonarcing voltage on the plug to see ionization throughout
the burn cycle).

I haven't tried these... but might soon ;)  (we might get to do more work on
the Formula SAE entry we put together last year... whee)

-ThorJ