MS3 PRO Knock Detection Thread
 

Ok so I've searched and read a lot of threads with the word "knock" in the title. But I have a few questions regarding how to setup and get knock detection working with a MS3. I have a MS3 PRO if it makes a difference. I know it has windowing and a lot of settings, it looks much better than the older stuff.

1. What knock sensor is best? Use the stock sensor? GM sensor? Something else? I have a BP that's bored to 84mm, so not sure if that really makes much difference for the stock sensor.

2. If I use the stock sensor, can I just tap into the existing wiring, or should I run a new shielded wire all the way to the sensor? Would it be better to run a new shielded wire?

3. What about settings for the knock control? Does anybody know what "works" well?

I want to try to do something using a knock sensor, and would prefer to not drop 600 on a J&S Safeguard if the MS can do the same thing just as well.

I know all about det cans, I use them.

I want this thread to be about using a knock sensor and software in the best way possible to have protection if something causes the engine to detonate.

I've played with mine a bunch but not been real successful yet. I can't get it to reliably detect knock and only knock -- either it misses knock or it falses on other noise.

--Ian

Thanks for the feedback Ian. How is your setup regarding my 3 questions? Stock sensor? Stock wiring? Stock sensor location? What settings are you running? Are you on standard 83mm bore or oversize?

Your results are what I've had a long time ago using a KnockSense MS, but supposedly the MS3 has a better system.

Yes, yes, yes to stock sensor, wiring, and location.

Settings in my build thread here:
https://www.miataturbo.net/build-thr...3/#post1215621

84mm Supertechs, Carillo A-beams, GTX2863R.

(edit -- updated knock sensor settings are here:)

http://www.codrus.com/miata/fm2r/May30/knock-may-1.png
https://www.miataturbo.net/attachmen...ine=1433056043

--Ian

Here are my settings:
1) Stock Sensor and wiring.
2) Initial settings per Reverant's Base map. (windowing and coolant scaling in particular)
3) Frequency filter confirmed by other info based on piston diameter.
4) Thresholds set by free reving logged values plus 15%
5) Gains based on makings the individual cylinder's values from free reving match one another. They make logical sense based on the sensor location.
6) I don't have Det Cans, yet, so confirmation of these settings is based upon places of MAP and RPM where the Knock Detection pulled timing. Then, when I reduced advance at those places, Knock Detection no longer detected. This demonstrates to me that the detection was based on a too-much advance phenomenon, such as knock.
7) I only get false trigger now when start kick-back occurred (during start tuning) or reving to redline and letting off quickly. I think this is likely gear noise or something like that.

https://www.miataturbo.net/attachmen...1&d=1433106208

https://www.miataturbo.net/attachmen...1&d=1433106208

https://www.miataturbo.net/attachmen...1&d=1433106208

The knock window settings are very very retarded. If you have peak pressure after 40 degrees ATDC you will misfire. I wouldn't start later than 20 degrees and wouldn't have longer than 20 degree window.

I don't know the code but it's most likely just looking at peak noise rather than integrating over a crank angle window. Therefore the knock window needs to be around where peak pressure would occur.

The top graph is BTDC. This is not a defense, just information.

So basically the window ends at 20 ATDC across the RPM range, and the beginning and window width are what changes.

So what would you recommend I set them at? Say listen from 4* ATDC to 24* ATDC? Something else?

I'm guessing that once you hit peak pressure, pressure is going down, and thus so is temp, so the odds of it detonating AFTER peak pressure is very very low? Or is this wrong? If true then windowing should stop after peak pressure of course.

I could have sworn I read in the help file that units were atdc for start of window, negative number is btdc.

Anyway you wouldn't want to start any earlier than about 8-10 atdc. At low speed you might have a longer duration but it's hard to say because there's no load component to the map. Low speed always wants to knock more, but it makes less boost.

High speed knocks less, but it makes more noise, Exponentially more.

The knock window settings were meant to start listening for knock a few degrees after the ignition event. I generally took the ignition timing at 75kPa or more absolute pressure, as pinging is - in my experience - unlikely below 75kpa.

For example, most of my basemaps have about 24* of timing at 3000rpm/75kPa. So I set the knock window at 3000rpm to start at 24*BTDC, then set a knock window duration of 44* to stop listening at 20*ATDC.

I hope this makes sense.

Was hoping you would come in. That's what I thought you were thinking on those windows.

Apology Accepted.

Got a question for you guys.

I got the knock sensor hooked up and software setup, but I'm showing 0.0% knock all the time. I actually cranked it this morning, and it showed nothing again, but then at one point I cranked it, and suddenly it was working! I tried tapping on the block and sure enough it registered knock. I thought crap, no idea but now it's working. Key cycled and it kept working. Key cycled again and it died, hasn't worked since.

I tested the sensor, it's good. I tested the wiring between the sensor, it's good.

I redid the wiring, still don't work. Swapped sensor for anther that also test good, still nothing.

Any ideas? I'm starting to think the knock module in the MS is bad...

One good way to test the module is to disconnect the sensor and connect your PC sound card to it. With the engine running, play a sine sweep file and see if the sensor responds.

Knock doesn't occur right after the ignition event. It has to go through the burn delay period first, which can be 10-20 degrees at full load, then bulk burn period-knock is much closer to area of 50-75 percent burn.

Translation : listening before TDC will only pick up noise.

Makes sense. Better windowing should result in better detection / rejection of false signals.

What I hear you saying is that the window should / can be a fairly uniform, Start at TDC, end at 25 ATDC, regardless of RPM. Is that a good interpretation?

What is your definition of "full load"?

*EDIT: Anyone have input regarding CLT scaling?

As a follow up, I did the test Matt described above and got no response, so I shipped the ecu back. Will report back once I get an update from DIY Autotune.

In the meantime, bump for this discussion to continue. :)

I have question for getting no-knock reference. It seems a lot of people set this by reving the enging in nuetral and using those values as a baseline.

Would it be better to pull say, 5 degrees from the timing table (guarantee a no-knock condition) and make pull from idle to redline, and use that as your baseline? Reason I ask, maybe the noise profile will be different under load?

Bump for input!

Also I sent my ECU back, DIY confirmed the knock module chip was bad and they fixed it under warranty! Awesome to see they support and stand behind their products.

It should be arriving today so I'm hoping to get the knock settings all setup and see how it works. I currently have my windowing from 8*ATDC to 28* ATDC.

For this I entered -8 for Knock Window Start, and 20* for duration. Does this sound correct?

MS3 PRO Knock Detection Thread
 

I would start with those settings. Then you can experiment with the window at certain rpms. I would keep the length at 20 degrees and move from -8 to something later (maybe move in 5 degree increments) to see if the detected values are noticeably different.