Knock Sensor.

[John Dammeyer]

> From: Bruce Plecan
> I want to throw together a knock sensor for my mustang.  I have no
> experience with them at all.  Anybody know how I should go about this?
What
> sensor, where to mount it, how to hook it up etc.  I was thinking about
> rigging it up to kill the power to the MSD box.
> Next spring I'll be well past the point where knock not only blows the
> gasket or pistons, but could split the block.  I'm moving to a T-Trim with
> new heads and custom cam.  Add the EEC tuner to the mix and I'm a
keystroke
> away from accidentally killing the fresh motor.
> Even a suggestion as to which sensor I should use and possibly a data
sheet
> for it would be helpful.
> Thanks for any help.

Hi Bruce,

We played around with a Knock sensor circuit for the Honda's but never ended
up doing anything with it.  Once we Turbocharge the little guy this may show
up again.  One circuit published in a flying magazine years ago just added
an op amp onto the standard Bosch Knock Sensor.

My SAAB service manual (1986 900 16V Turbo) shows the sensor orientation is
also important;  the wire connector angled so many degrees off vertical.   I
also recall an article (from Motorola I think) about actually doing a
spectrum analysis to determine what was engine noise and what was knock;
it's a very narrow frequency where knock occurs but unique to the engine.

I also recall that SAAB only reduced timing on the cylinders that were
causing the knock whereas the circuit I designed just did a blanket retard.
However,  since the 100HP Honda's never had the knock sensor attached we
never tested it in real time.  All we did was tap the sensor on the block
while the engine was running and watched the timing retard for a number of
strokes.

Cheers,

John


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