I have built the knock sensor, and wired the input of the circuit to the yellow wire on the knock sensor. But it is not detecting any knock.

I wonder if having the stock ecu still connected to the sensor would affect its output enough to not register any knock.

I tested for knock by banging a hammer near the knock sensor on the block.

Anyone else got this to work right?

Knock happens at a certian frequency, there is an equation floating around somewhere which relates cylinder bore to knock frequency. I believe the stock knock sensor is looking for that certian frequency.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

Isn't the knock sensor already tuned for our engine? When that knock sensor sees knock, it would output a pulse which the MS circuit should pick up?

you are correct but the knock sensor is not sensing vibrations. When knock occures the sensor picks up on a harmonic frequency within the block. If the sensor operated on vibrations then the ECU would have false readings during daily operation. Even piston slap would set the knock sensor off.

The only way to test would be to either send a simulated signal to the MS or to tune really lean and knock the motor. if your on factory ignition then you will know when you knock!

My snap on scanner reads the knock sensor in terms of voltage, not sure if the MS will read the same way or if the factory ecu reads in the same manner. I havent had a chance to really look into how the factory sensor signal operates.

Terry

Don't you think that we need this to work properly to detect knock with MS and further more, detect when our timing adjustments are getting dangerous?

If you listen very, very carefully you can get by without a knock sensor. It's much better to have a circuit, though.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)