Knock Sensing

[Buchholz, Steven]

Some time ago I found a reasonable reference on knock detection on TI's
website ... I checked and found it is still there ... here's an abstract:
ENGINE KNOCK DETECTION USING SPECTRAL ANALYSIS WITH TMS320C25 OR TMS320C30
DSPS - An efficient method of detecting combustion engine knock is using
spectral analysis. The detection process algorithm adapts to a no-knock
reference at varying speeds and loads by using multiple frequencies. This
document presents an problem overview, current technology, and two
implementation examples are given to aid in the development of system
specific hardware and software. The first system is based on the 32-bit
floating-point TMS320C30 DSP with software written in C. The second is
production oriented using a TMS320C25 16-bit fixed-point DSP and assembler
software. The appendix contains the code for each implementation. 

	http://www.ti.com/sc/docs/psheets/abstract/apps/spra039.htm

I have been contemplating the addition of a knock sensor to an engine which
did not originally have one so that I can start tweaking the performance.
While this reference does give a good background into the whys and hows from
a DSP standpoint, it doesn't go into strategies for mounting sensor(s) for
best results.  Are there any references that discuss this sort of issue?
Does anyone know any companies who actually make the sensors?  I'd love to
see specs for typical sensors (frequency response and such).  The TI
reference states that there are two types of "indirect" knock sensors, ones
that are tuned to specific frequencies and broadband units.  From what I've
seen I'm thinking that most if  not all of the knock sensors I've seen have
been tuned units to minimize the amount of subsequent processing required.
It seems to me that if one were contemplating adding a knock sensor to an
engine, the broadband approach might be the preferred solution.  

Steve Buchholz
San Jose, CA (USA)