To answer Zaphod's question, there needs to be an additional "AM type detector" circuit between my circuit and the MS, and it sounds like the above-mentioned GM circuit functions as such.

Would it work properly with a Bosch wideband sensor? Or OEM wideband Miata sensor only?

What is the recommended minimum power rating for the resistors? (If one is trying to stuff it in as small packaging as posible)

What does the Bosch sensor take for phantom power?

If you give me a datasheet I can tell you for sure.
2nd best would be an existing schematic for the front end of one -such as the old Link, which IIRC, uses the Bosch wideband.

here's a pdf of the datasheet

http://www.bosch-motorsport.de/pdf/s...knock/KS-P.pdf

What would your filter/amp increase the max output voltage of the 1v Bosch knock sensor to? Or would it?

The bosch sensor is a piezo non-resonant sensor. (No need for phantom power).

Therefore remove R19.

However I have to look at the size of the signal to decide if the "gain" of my circuit needs to be reduced.

Anyone have the miata knock sensor datasheet? I vaguely remember its signal is 1/30th of the GM resonant senors though...

I can't find the msm knock datasheet anywhere.

Are you saying that the above circuit boosts a 0-0.033 volt signal to a 0-5v signal?

This is what John at J&S says about the output difference between the Bosch and the GM resonant ones:

"The output of a resonant sensor is about 500mv/g, while that of a non resonant sensor is about 20mv/g.
An example of a non resonant sensor is the Bosch sensor, which requires a shielded cable."

Hmm, that doesn't tell me the difference between either of them vs. the miata factory sensor, which is what I need to know.

I will guess that my circuit is in the ballpark. Its output is designed to mate with the AEM which I presume is designed for the resonant sensors, and its gain is close to 20x, and the bosch sensor is 1/25th the output of the resonant sensors.

Maybe these can help

?

Hmm
http://expresspcb.com/ExpressPCBHtm/SpecsMiniboard.htm

The can do 3 pcx 3.8" x 2.5" boards for $51 + shipping sent out the next day.
Each one would probably fit 3 of the circuits, maybe more, so you get at least 9 for $51.
All we need now is someone to lay it out in their free software.

They are certainly not the only house which turns boards cheap. :-) I did a set of ~7x4" boards maybe 11 of them for $150? At least I didn't have to do it in their software.

So this circuit just does the filtering/amplification - i.e. no analog levels out, no RPM or angular dependent filtering?

Yep, just need a simple bandpass filter, perhaps adjustable with a simple pot to vary bandpass frequency a bit. Adjustable gain is probably not a big deal but it would be nice. Output signal should be low so it does not overdrive the Adaptronic's input. :2cents:

digging this back up for a couple reasons.

https://www.miataturbo.net/attachmen...4&d=1234115619

The latest MS3 alpha firmware has experimental knock sensor and windowing settings.

To reconfirm, this circuit provides a 0-5V amplified, bandpassed knock signal from the stock NB sensor, correct?

Yes, but the output is an AC knock signal, with the same amplitude as a tuned piezo sensor.

I would like to point out that the center frequency should be moved from 13 khz to 6.5 kHz. Higher RPM knock is more centered at 6.5 than 13 khz.

To change it quadruple the sum of the values of C9~C11, and approximately halve R20 and R21.

AC knock signal? as opposed to what?

Presumably as opposed to the binary 0 or 5v signal produced by the KnockSenseMS or the 0-10v signal produced by the original GM ESC module on which the MS's knock sense feature was originally based, which conveys a simple "knocking" or "not knocking" indication, rather than merely acting as a bandpass filter and amplifier as this circuit does.

In other words, the Megasquirt's knock-sensing capability is rather primitive. It is not able to read an analog signal (even one that's been filtered and amplified) and do the comparison to determine whether or not knock is present on its own. It needs to have an external device do the hard work, and then simply send a binary signal to the MS telling it whether or not knock is present. (At least, that's how it is on MS1 and MS2. I assume MS3 is the same.)

Correct. (1st paragraph)

ok but the AC is all happening from 0-5V... which sounds like what I'm after.

Here is the new knock settings dialog:

http://y8spec.com/megasquirt/images/...ha11knock1.png

and if windowing is desired:

http://y8spec.com/megasquirt/images/...ha11knock2.png

note that you can output the window to external knock devices for some reason.

A TPIC9101 does not show up when I google so therefore it doesn't exist to me.