Detonation Sensor DIY help

Hi,
I'm new to this forum,I live in Portugal(unfortunatly) only able to write in Eng. but understand most Francophone writing.
I am an electronic technicien by trade and like to build and improve 2 strokes as a hobby.

I do all voltage regulators/power supply and some of the instruments on my bikes

I'm drawing a circuit to process the signal from a Bosch wide band knock sensor from a car,but I need to know which frequency range to monitor and detect on a motorcycle two stroke.

A pratical test would give the data I need but I have no conditions to preform such a test at this time,I can't do much more than office work,situation I hope will change.

Far from asking someone to preform a potentially destructive dangerous test,my request is for someone who might have the knoledge and won't mind sharing it,I did find a analog circuit floating around on the net based on an amp-op array and hi/lo pass LC freq. filtering net (3.5/6kHz if my memory is right) but it doesn't mention what size and kind of engines it was made for,I think a big 4 cyl.4 stroke will produce a different signal?

Any views welcome,thanks in advance.

The data from a knock sensor is not a frequency but a voltage ...

You get it with a piezo sensor like that

[Vous devez être inscrit et connecté pour voir ce lien]

To get a calibration , i would compare to an HRC unit with dataloguer and the fix the V graduations of the deto as you can find in the dataloguer HRC

SEB4LO a écrit:

The data from a knock sensor is not a frequency but a voltage ...

You get it with a piezo sensor like that

[Vous devez être inscrit et connecté pour voir ce lien]

To get a calibration , i would compare to an HRC unit with dataloguer and the fix the V graduations of the deto as you can find in the dataloguer HRC

as long as you mention any frequency has a tension measred in volts,dB

there is no V graduations ther is a tension measured in Volts.

But dataloggers usually log n. of deto events, not sure what you mean
but don't get me wrong I apreciate the effort to help I assume


The piezoeletric accelerometer (aka knock sensor) measure G force and generates a voltage as result,that can also be express in dB.

a detonation will reverberate in a specific frequency inherent to the engine type,I got this from a car,but it is a wide band sensor and I do have the data sheet

it also detects all the mechanical noise hence the need for filtering

Level calibration is a no brainer


if you have a HRC laying about I can borrow,I'd appreciate because had I the money to buy one I wouldn't be building it.

I will publish a circuit diagram with a bright led VUimeter monitor,3 digit counter and debounced I/0 logic output to drive for ex. a back off advance for the CDI or switch a 2nd curve
All with standard components

I'm asking for a kHz figure for a 2 stroke

[Vous devez être inscrit et connecté pour voir cette image]

Perhaps this can help: [Vous devez être inscrit et connecté pour voir ce lien]
I cannot vouch for it though, my knowledge is limited..

There is also this unit -as a knock monitor gauge, not deto counter- which might save you from the trouble altogether: [Vous devez être inscrit et connecté pour voir ce lien]

Vagelis a écrit:

Perhaps this can help: [Vous devez être inscrit et connecté pour voir ce lien]
I cannot vouch for it though, my knowledge is limited..

There is also this unit -as a knock monitor gauge, not deto counter- which might save you from the trouble altogether: [Vous devez être inscrit et connecté pour voir ce lien]

Hi,that's great it helps a lot.thank you.

The formula must be close enough as it agrees with the data I gathered so far and being that a two stroke doesn't have a noisy valve train I probably can broaden the filters bandwidth

The avejas knock amplifier,I have a circuit that should be very similar to that .
I saw it before,my concern was that box it set to work on 4 stroke car engines,but adding a counter is very easy.

I will now calculate the new RC net with a 4kHz bandwidth centered on 10kHz for a 56mm piston since my cousin has a DT125R which I hope to use for testing,and will start building the board .

Thank you