Stock knock sensor voltage output?
#1
Elite Member
Thread Starter
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Arrrrghhhhhhhhhhh!!!
So how much voltage do you guys see from your stock knock sensor? I am only seeing like 0-.3v Yes, that's point 3. 0.3 Isn't this ****** supposed to put out 0-5v? fukk!
I am running a hydra but it shouldn't matter. volts is volts and the knock sensor plugs right up into the hyudra.
So how much voltage do you guys see from your stock knock sensor? I am only seeing like 0-.3v Yes, that's point 3. 0.3 Isn't this ****** supposed to put out 0-5v? fukk!
I am running a hydra but it shouldn't matter. volts is volts and the knock sensor plugs right up into the hyudra.
#2
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I'm not familiar with miatas specifically, but in general a knock sensor is just a microphone. There is usually a "knock box" which interprets that signal and converts it into some sort of higher voltage signal for the benefit of the ecu. I suppose it would be possible to have this circuit integrated into the ecu, but usually it isn’t.
#3
Boost Pope
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/smod.png)
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,339
Total Cats: 6,793
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
You can't plug a microphone directly into a loudspeaker, right? Gotta have an amp and probably some EQ in the middle. Same deal here.
#5
Elite Member
Thread Starter
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
OK, right, well it's not plugged up directly into the Hydra ECU--- it is actually going through the stock wiring up to the factory ECU harness which then plugs into the hydra harness which then plugs into the hydra.
Sooooo in my Hydra readout I'm only seeing these fractions of volts.
If the stock sensor is phantom powered then it would need two power lines, not one
Sooooo in my Hydra readout I'm only seeing these fractions of volts.
If the stock sensor is phantom powered then it would need two power lines, not one
#10
Elite Member
Thread Starter
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
BALLLLLSSSSSS
OK I will search.
Thing is this **** used to work before I ripped out my old engine and upgraded hydra to 2.6. Voltage at hydra used to be 0-5v proper like. Now it is piddles.
OK I will search.
Thing is this **** used to work before I ripped out my old engine and upgraded hydra to 2.6. Voltage at hydra used to be 0-5v proper like. Now it is piddles.
#12
Elite Member
Thread Starter
iTrader: (2)
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,682
Total Cats: 130
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Doesn't mean that your sensor isn't detecting anything. I'm sure if you try hard enough you can get it to register a full 5v. With the Hydra you have the ability to set the threshold. So as long as you have the threshold set at a proper level, then it will function as it is designed.
#15
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Also keep in mind that a knock sensing circuit doesn't go by voltage alone. In fact, a steady 5 volts, if you shorted the knock sensor output to the TPS reference voltage attempting to test things, for example, probably wouldn't trigger it. At the very least, it will look for the signal to be coming in on a specific frequency close to the frequency knock would make. A more sophisticated setup may even only respond if the sound comes in within a set time of the spark firing or have other criteria.
Thread
Thread Starter
Forum
Replies
Last Post