Safe knock voltage

[justin0469]

So I have looked around and can't really find my answer. When I read knock voltage, it is just sounds in the engine bay that the ECU has yet to determine as knock or not. In general, how much knock voltage is normal for typical noise that is not knock?

 

[luvmygst]

What I would like to know is at what voltage does the computer say "Oh thats knock" There has to be a cut off, but does anyone know what it is?

 

[steve]

So I have looked around and can't really find my answer.

What didn't you understand the last time you asked this?

http://www.dsmtuners.com/forums/showthread.php?t=219925

Steve

 

[justin0469]

I did understand, but that is not answering my question. I understand that the ECU determines from the knock sensor what is actual knock and what is not. But it still gets it from the knock sensor voltage.

 

[steve]

Again, there is no specific voltage that represents knock from our sensor.

It's sound picked up by the knock sensor and processed inside the ECU.
People have hooked up an amplifer and listened to it but that's pretty much the extent your going to be able to do anything with it. That is unless you want to start describing your background in DSPs.

Steve

 

[justin0469]

OK, maybe I should rephrase it. When anyone is just driving around. what is the typical knock voltage? If I am seeing 0.14V, is that what everyone would be seeing given the same driving circumstances? Is a knock voltage around that most likely alright? What is the range of the knock voltage?

 

[steve]

Rephrasing your question doesn't change the fact that what your asking doesn't relate to how things work. I know you want the answer to be easy but it's not. There is nothing you are going to be able to do with the knock sensor signal other than check to make sure the the circuit is functional.

You could be getting a 0.14v reading and knocking like crazy or not knocking at all. It's the spectral content of that signal that would tell one over the other.

I'll look tomorrow and see if the 2G FSM gives a typical voltage for the knock sensor.

Steve

 

[justin0469]

So the voltage shows no hint as to how loud or how much noise or knock there is? So really then, reading knock voltage has absolutely no benefit?