Using a knock sensor from one engine on another

[Eric Fahlgren]

TVS wrote:
> 
> I assume the frequency has some dependence on variables
> like bore diameter and combustion chamber shape, but is the knock detection
> circuitry likely to 'listen' for a wide range of frequency's or just a
> narrow band?

I don't think bore has much bearing.  I've always thought that the
bore was a single variable in the excitation function, but that the
response frequency was determined by the structure (i.e., the block/head
et al).  Imagine a 10 oz hammer ringing a bell whose principal mode is
100 Hz.  What do you hear?  Mostly 100 Hz.  Strike the same bell with a
10 lb sledge.  Still pretty much the same response.

Here is some info (resonant frequencies of knock sensors) that will probably
be of interest to you:

   http://acc-electronics.com/cloud/images/page3_55.jpg

Check the second and fourth columns of the table at the bottom.
It looks to me like there isn't any correlation between the
knock sensor's frequency and any of the obvious engine parameters
like bore and stroke (but then again I didn't do any real analysis).

-- 
Eric Fahlgren                            Mechanical Dynamics, Inc
efahl at adams.com                          Ann Arbor, Michigan, USA
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