Anyone have any information on making your own knock monitor? Maybe something that can monitor the voltage off the stock sensor? Knocklink seems pretty expensive for such a simple application.

 

If someone can give me the voltage range for the knock sensor, I could easily fab up a LED display for reading the knock sensor (yellow led for mild knock, red led for more knock, etc)



I have actually seen a knock sensor readout somewhere...but I can't remember where I saw it.

 

yeah thats exactly what I thought of doing but I am not an electrical engineer I know what needs to be done just don't know how. Someone the know what the voltage values are? I got a cusin who can probally make me something but I need to know the values.

 

I read somewhere on here that the knock sensor wire going back into the ecu was 0-5v. I haven't checked it out though...

 

yeah but i want to make something to monitor that voltage and turn LED's acording to the output. Increased voltage = knock. Just need to know how much voltage is bad so I can make something similar to a knocklink.

 

Here is the link to Knocklink.

http://www.link-electro.co.nz/knocklink.html

This is the knock sensor "gauge" that I saw before.

As for building one yourself, I can easily do the electronics, but I would not be able to create a nice plastic enclosure and display like the knocklink. Basically what I had planned to do a while back was just mount 2 led's in the A Pillar gauge pod under the AFR meter. 1 yellow and 1 red (as described in my other post^)

 

Yes the stock sensor is 0-5v sensor.

For your purpose I would say above 2.5 volt would be YELLOW and above 3.5 would be RED. But I would be really nice if you could build one so you could coose calibrations! That my friend could make you some bucks. Just a switch for 2-3 different calibrations. As you make more power the car will make more noise is the main reason why I recommend it.

Switch 1
<=2volts would be Green
<=3 volts would be Yellow
>3 volts would be RED

Switch 2
<= 2.5volts would be Green
<= 3.5volts would be Yellow
>3.5volts would be Red

 

knock sensor is just a microphone that records engine noise, it's up to the ecu to determine which sound frequency is knock. i don't think a microphone will have a voltage variation between 0-5v

 

it is a 0-5v but i think its VERY weak.

we have been discussing this in the vishnu forum for a while, because i wanted to log knock sensor activity with my LM-1 wideband controller.

 

Building a knock sensor like you speak of will not tell you when your are knocking or not...it will simple measure voltage.

The ECU determines knock by constantly adjusting what is an acceptable range for the backgound noise due to various conditions, such as RPM ,etc. The ECU learns what the normal range of the background noise is and pulls timing if their are any voltage spikes anywhere in the RPM band above that acceptable range. The amount of the spike, sometimes called knock counts, is directly proportional to the amount of timing that is then pulled by the ECU.

For example, on the DSM ECUs (I'm not sure about the EVOs yet), 3 counts of knock will pull 1* of timing.

But my point is that the knock sensor is monitoring the background noise of all 4 cylinders. That background noise looks like a ton of little up and down spikes. That range of spikes is considered 'normal' and no knock as long as their aren't big spikes. It's sort of hard to explain without pictures, but determining what is knock is not as simple as building a voltage reader. You need to know the acceptable voltage readings for your setup and the RPM that you are at. Also, the acceptable range will change with mods, age, etc, so having a static monitor will do you no good.

Eric

 

The knock sensor should be a crystal that creates a voltage when it is "excited" by the pulses of the "knock". When you apply pressure to a crystal, you get a corresponding voltage out...more pressure=more voltage. From this I assume that the crystal is already pretuned to the "frequency" that spark knock emits, and sized so as to emit a known voltage range.
All I was going to do is monitor the output volotage of the crystal. smaller noises would be ignored while larger noises would read. I would accomplish this using an IC chip that incorporated zener diodes. Of course I would have to pick the IC with the breakover voltages preset so I couldn't "tune" it on the fly, I would just have to get the correct IC with the correct breakover voltages.

Someone correct me if this is not how a knock sensor works.

 

That still wouldn't necessarily work because you are just looking for a statically defined voltage number. That is not what knock is. Actually, knock is much more likely to happen at torque peak, which is roughly half of the RPM range for our cars, where the background noise is going to be less than the background noise at the rev limit. If you build something that detects voltage above a certain number, then you may very well be missing a lot of real knock in the lower RPM ranges, because you will have to build the voltage reader with a limit above your maximum background noise.

Do you understand what I am saying? Background noise is in the shape of a parabola, like an exponential rise with RPM. So, your knock detector will have to also be able to monitor this rise, just above the normal background noise. Any signal above that 'normal' line (which is that exponential, curved shape) will be knock. Any spike above the normal 'curved' voltage for that range.

You cannot accurately detect knock by simply picking a preset voltage.

Eric

 

im suprised more companies dont have something like this for the evo.. should be a pretty essential device for modified cars and this knock link is the only one out there?

 

There are others and there is J&S Safeguard also.

I use knocklink.

 

i saw site some where before about DIY knock detector. it was basically an electronic hearing aid device from radio shack where they mounted the microphone near the engine in the engine bay and the amplifier/speaker in the car, and you can listen for detonation inside the car while you are driving.


just found the link
http://autospeed.drive.com.au/cms/se...&Search=Search