knock sensor question

[wakotow]

How can I replicate the knock sensor signal so the ecu will go to the knock maps. Do I just need some random frequency (tapping on the sensor) or do the knock sensors only 'activate' at certain ones? What are those specific frequencies/ranges?

Also if any of you have oscilliscope printouts of a knock sensor under normal conditions and during knocking that'd be awesome, I couldn't really find anything like this on google.

[wakotow]

no one knows how a knock sensor works? How does the ecu decide it's knocking, what sort of voltage/frequency does it read as knock?

[Carl H]

its basicaly a frequency response device but you can measure resistance across the sensor and just shove the appropriate resistor inline to 'defeat' the knock sensor.
quick and dirty but effective.

[wakotow]

Actually I'm trying to 'activate' the knock sensor. I want the ecu to go into knock, or at least think it's in knock. How can I pull that off, just supply a voltage, or do I need to supply a (not flatline) signal?

[Carl H]

disconnect the knock sensors, it will force the ecu into knock maps and throw the knock code.

[wakotow]

awesome, thanks!

[eh?]

If you still want to know:

Knock frequency for our motors is about 6.7khz . It's supposedly based on bore size. From my research the rb20/25 has a "narrow band" knocks sensor and hitting the motor with a hammer will not do anything.

[wakotow]

that's fantastic, thank you.