Knock sensor
Pete Paraska
paraska at oasys.dt.navy.mil
Thu Jul 21 14:51:10 GMT 1994
Dave Williams wrote:
> SAAB's Trionic engine management system drops voltage after the initial
>spark, then looks at the resistance of the plug gap. SAAB claims they
>can tell if the cylinder is running into detonation by looking at this
>value.
Just interested in other's ideas how this might actually work. How could
plug gap resistance after the spark tell you anything about detonation? Can
the plug gap "taste" the residue of preignition as being different from the
"taste" (er..resistance) of a slowly propagting flame front that results
from correct ignition?
It's an interesting concept, though, using plug gap resistance to measure
detonation. If it was repeatable and reliable, it would seem to be better
than trying to guess what that accelerometer (knock sensor) was REALLY
telling you.
It seems that all this filtering, amplifying, etc. and making assumptions
about what frequency is actually indicative of detonation involves several
leaps of faith.
~~~~~~~~ Pete (paraska at oasys.dt.navy.mil) IZCC#15 ~~~~~~~~~
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