I was just thinking today... how does a knock sensor work?

For those of us without any kind of computer control, it would make an interesting tool if you could use the factory knock sensor that fits in the block turn on a light when it senses spark knock. Like an idiot light I guess It might make a nice tuning tool to use at the track to get the most out of the engine without having it spark knock. Would be especially helpful on the louder open-exhaust cars, where you can't hear spark knock at all.

How could something like this be wired up? Can it even be done?

 

The knock sensor is a crystal that vibrates and sends out a signal voltage. I would think that if you taped into the output wire, it might change the signal that the computer gets.

 

Well, my knock sensor isn't connected to anything anymore... no more computer in my car. Its just an expensive drain plug at the moment

So would there be a way to get it to set off a small light if it sensed a knock? Like, does it just ground out, like a fan switch?

 

I built a stand alone detonation indicator from some plans I found on the net. It can be built using a handful of cheap electronic parts all available from Radio Shack.
I installed the knock sensor on the drivers side and left the passenger side sensor installed for the ECM.
The plans use a bright LED, a buzzer, a test button (for the light and buzzer), and a switch so the buzzer can be shut off if desired.

Once installed, you have to force the eng to knock;
then adj a sensitivity pot (while it's knocking) so it actuates.

All the parts cost abt $15 (not including the sensor).

The guy that originally posted the pics/schematics had it installed in his motorhome.

I think I still have the pics/schematics at home somewhere. I can post them in a couple of days if anyone's interested.

 

Yes, please post them!

 

Adam this was the best info I could find.......it is a sliding scale of output depending on RPM..... normal knock at 1k is around 1v AC to around 8.5v AC at 3k

 

I couldn't locate the original pics I had but here's an elec schematic I posted a while back abt it.

https://www.thirdgen.org/techbb2/sho...ighlight=knock