Jim Baker
Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA
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 Posted: Sun Oct 14, 2007 8:38 am Post subject: (Fwd) Re: Knock sensors? |
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| Quote: | I read years ago that knock sensors were tried but didn't work because
with the piston slap that is present in air cooled aircraft engines
makes it difficult for the sensor to determine the difference between
piston slap and 'knock.'
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Can't speak to the whole issue but...
I live a short ways from GAMI at Ada, OK. While over there one day I asked
about their electronic ignition. They're using an optical sensor (laser pulsed
into the cylinder via a fiber optic cable situated on an offset spark plug). The
regular 18 mm plug has the cylinder offset axially from the center and the
fiber optic is positioned on the other side. The laser detects the onset of
detonation through some sophisticated algorithims looking at charge density
and flame front propagation (as they explained it to me). GAMI chose the
nastiest engine known in terms of detonation sensitivity, a TSIO 540. They
can virtually feed this beast almost anything combustible and it runs without
complaint. They even demonstarte changing fuel types during a full power
test cell run and you'd never know anything had changed except by watching
the timing and EGT changes on the data screen. Its been a year or so since I
saw it in operation and don't know their current status for certification testing.
Jim Baker
580.788.2779
'71 SV, 492TC
Elmore City, OK
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