copper pipe knock detection

[Axel Rietschin]

> More info on this system for knock detection please,
> it sounds cheap and feasible.

Just take a small pipe, maybe 12mm (~1/2") of sufficient length. You squeeze
an end over 2-3cm (~1"), drill a hole in the flat you just created and bolt
it somewhere more or less directly to the head casting, perhaps on an intake
manifold stud. The pipe has to be routed avoid contact with other parts of
the engine. At the other end you hook up some sort of Y piece and soft
plastic pipes, then you somehow build a 'headphone', perhaps based on the
hearing protectors used by people firing guns, to give you some level of
insulation against ambient noise. This works very well as long as you can
sufficiently insulate yourself from the engine noise; you can use several
meters if pipe if necessary.

Another cheap and readily feasible approach would be to use a standard
(piezo) knock sensor as a microphone, hooked up to some audio gear like a
portable tape recorder, and then use an audio headphone (of 'closed' type,
and good quality such as the Sony MDR-7506) to listen to your engine
internals.

I've found that the piezo sensor and recorder worked slightly better at mid
rpm mid load but the copper pipe was most effective at high speed, i.e. the
knock-to-noise ratio was better.

--Axel


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