Has anyone done this? How do I do it?

 

the LC1 only logs the actual input from the sensor. You would need an auxiliary device that can log the frequency produced by the sensor. and then it has to be interpreted or filtered. a knock sensor isn't just a linear 0-5v signal like a TPS or something

 

Any idea what the frequency range is? I have a multimeter that does frequency. Wouldnt be to good for a permanent thing but as a tuning tool it might be handy and better meters do have a logging feature.

 

that's from a Turbo II technical data page

note that there are basically two styles of knock sensor used by manufacturers. Some will produce a signal only in what the engineers believed to be the knock frequency range range, and doesn't make much voltage outside of that. That's called the resonance type. The other style of knock sensor is always producing some kind of voltage and it is up to the circuitry and control logic to interpret the signal. That is called the mass type. I suspect that Rx-7's use the mass type.

I can log the factory knock sensor with my Power FC in the same way that I can log an FD's knock sensor. The Power FC spits out a live "knock count" reading (I am not sure what triggers it) ranging from 0 to at least 120. It has to be some measure of noise, either the frequency or amplitude of the signal. On my car reading the stock knock sensor isn't particularly useful. The signal tends to increase with revs and I think is heavily affected by motor mounts. I have a friend's FD that I tune and his knock sensor seems to be marginally more useful. I think the FC and FD knock sensors are very similar.