I finally got around to building and testing an audio amplifier
for the stock Mazda knock sensors. Works great! Here is the
skematic right out of the National Semi data book.

The wire coming from pin 6 can be connected to a nine volt
battery for a power supply or run off a regulator from
the airplane 12 Volt supply. You will need one of these
per rotor. Don't worry the chip is cheap. You can buy them in
Radio Shack for only a few bucks each. Most of the other parts
can be had there as well. I used an Radio Shack earphone in 
place of the speaker and it worked great.

The stock Mazda knock sensor is connected to the top of
capacitor C9. There is only one wire from the knock sensor
so no big deal. I ran the amp flat out by connecting
a 10 mfd cap from pin 1 to pin 8. This gaves a gain of
200. I could just tap the rotor housing with a hammer
and hear it in the earphone.

I highly recommend some sort of knock sensor if you are 
turbocharging your engine. Knock can ruin your engine in
short order by fracturing the apex seals. The engine won't
stop of course but your expensive rotor housings 
will be scratched.

Cheap insurance when setting the timing or boost on your
turbocharged rotary.

If enough people express an interest I could build a pc 
board and put together a kit of parts. It would have three
knock sensor amps so those with three rotors will be served.

Paul Lamar
 
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