DIY_EFI Digest V5 #16:Knock Sensor

[Carter Shore]

Some requests for the software I'm playing with.
It's a program called 'spectragraph', available for
download at: www.monumental.com/rshorne/gram.html

There may be other better ones out there, but this one
seemed to fit my needs.

If this works, maybe we could keep a library of 'knock
signatures' by engine.

There's an app note for a chip that does FFT for KS,
but maybe overkill; if you can find the fundamental
resonant knock freq with better than 6 dB S/N ratio,
why look any further? 

On the other hand, multiple mics and holographic audio
imaging could allow you to pinpoint not just knock to
the individual cylinder, but maybe detect impending
bearing failures etc. before they go catastrophic.
What about an 'active' electronic crankshaft damper
that attenuates 'on the fly'.

Oops, sorry for the geek out. Anyway.

I wonder what kinds of things might influence the
knock signature? Maybe forged vs cast crank? Certainly
aluminum vs cast iron block/heads. Maybe the intake
manifold or headers. Aluminum flywheel? Different
crank dampers? Would the KS change if you used filler
in the water jackets? What about just bore/stroke
changes? Operating temperature? Manual vs auto trans?

Lot's of questions, no answers yet. Might be it just
doesn't matter. We'll see. Could be fun.

Carter

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