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Old 03-13-2012, 09:01 AM   #1
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Default Knock control on the MS2

Finally, after many obstacles, the latest version of my Enhanced MS2 has the foundation ready for proper knock control.

Input from the knock sensor on the processor pin. It is already filtered through the DSP stage:



What the MS2 sees:



Now, for the firmware changes...
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Knock control on the MS2-knock_input.png   Knock control on the MS2-knock_graph.png  
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Old 03-13-2012, 09:06 AM   #2
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Great work Reverant
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Old 03-13-2012, 09:22 AM   #3
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Raw stock knock sensor output (pink) Vs the filtered output going to the MS2 (yellow) - you can see that the stock sensor is of the resonant type.

Sudden knock:



Reaction time of the DSP stage (~1.7ms):

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Knock control on the MS2-scope_0.png   Knock control on the MS2-scope_1.png  
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Old 03-13-2012, 09:53 AM   #4
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You are such a bauce.
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Old 03-13-2012, 10:29 AM   #5
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As a electronics noob, I don't know what all of the above scopes mean - but I have to ask - is it an extra board? Will it work with MS3? (Or should I really wait until James board is available again...?)

Greets
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Old 03-13-2012, 10:35 AM   #6
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It is on my expansion board. I can make it work for the MS3 (or do a separate "knock-only" board) however I don't want to have a "competing" product with James. So wait for his board again.
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Old 03-13-2012, 10:57 AM   #7
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O.K. --- that is what you get for stepping up to MS3... ;-)
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Old 03-13-2012, 11:21 AM   #8
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Quote:
Originally Posted by Zaphod View Post
O.K. --- that is what you get for stepping up to MS3... ;-)
what's wrong with that. you can pinpoint what clyinder is knock and adjust the fuel/spark trim per clyinder.
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Old 03-13-2012, 11:47 AM   #9
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the latest MS3 beta firmware (yes, I said beta) does a pretty decent job of utilizing the knock signal. it's a little hard to sift through all the noise in the logs (actually beta 19 seems to forget to log the raw per cylinder values) but the peak-decay combined value is logged.

also the windowing is pretty nice because you can see exactly what cylinder is making the most noise and retard or enrich on a per-cyl basis.
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Old 03-13-2012, 01:14 PM   #10
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Subscribed.

Reverant, just to be clear:
- Will current owners need our boards' hardware updated?
- Are any other wiring/hardware changes on the car needed?
- Will the severity of the knock be detected to allow for gradual mitigation (timing/fuel adjustments in steps)?

I really appreciate your persistent work - I know this has been on the way for a long time.

Cheers,
- Tom
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Old 03-13-2012, 01:20 PM   #11
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Quote:
Originally Posted by one-niner View Post
Subscribed.

Reverant, just to be clear:
- Will current owners need our boards' hardware updated?
- Are any other wiring/hardware changes on the car needed?
- Will the severity of the knock be detected to allow for gradual mitigation (timing/fuel adjustments in steps)?

I really appreciate your persistent work - I know this has been on the way for a long time.

Cheers,
- Tom
1) Yes. This is a totally new expansion board design. In fact, this is board version 2.0 for the MS2V3. You have a DIYPNP, which makes things even more complex (having said that, my own DIYPNP has the V1.0 of the expansion board, I need to upgrade my ECU as well).
2) No other changes needed on the car.
3) The severity of the knock is detected as you can see, the signal fed into the MS2 is analog. My plan is to give a proportional retard option - ie retard 4* if the knock is 40%, retard 7* if the knock is 70*.
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Old 03-13-2012, 01:29 PM   #12
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Ok, thanks for the swift response.

I guess I'll see how things progress from here and then perhaps we can discuss options once I go F/I - I really have my fingers crossed that CCR Racing will get their '99 kit approved soon

- Tom
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Old 03-13-2012, 01:44 PM   #13
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Great much-needed work!

Will you share with us how you discriminate knock from background noise? Do you:

- Compare noise levels during the valid knock crank-angle window against outside-the-knock-window?
- Just compare noise levels during the valid knock window against a background-noise-vs-RPM plot?
- Don't do any crank angle windowing?
- listen for the telltale "descending bell" note?
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Old 03-13-2012, 03:42 PM   #14
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Right now there is no knock windowing, although I have provisions on my current board for it. If my free time permits, I will see if I can actually make it work.

The method to be used will be simple:

- Only look for knock inside the knock window
- Noise outside the knock window will not be used at all (this is a limitation of the MS2, I would use it if I could)
- Display the knock percentage. User decides the knock percentage threshold which triggers the knock reaction system. The threshold is the noise profile of the engine at various RPMs. Probably an 8-point table.
- May add a sensitivity adjustment (factor) based on MAP, IAT (higher MAP or IAT = more likely to knock, so make it more sensitive)
- Once the knock threshold has been crossed either remove a given amount of timing until no knock is there, then gradually restore the timing back (current MS2 strategy), or, given that we have an analog signal in now, reduce timing proportionally to the knock intensity, and gradually restore it.
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Old 03-13-2012, 04:11 PM   #15
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Will this 1) work with my knocksense MS unit and 2) be easily added to my (theoretical for now) MS3X?
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Old 03-13-2012, 04:16 PM   #16
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This is for the Enhanced MS2 that I build only. It is an integrated solution, there is an expansion board inside the case, much like the MS3X board, that has the knock solution on it. For the MS3, you need to get Jame's (jsmcortina on msextra.com) knock board. I would get this and install it for you, however he does not have any at the moment to sell.
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Old 03-14-2012, 11:17 PM   #17
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What exactly do you define the knock percentage as?
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Old 03-15-2012, 04:12 AM   #18
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The knock input is a 0-5V analog signal. Currently, 100% is a full 5V. I can however, set the knock levels (0 and 100%) as configurable levels (ie 0%=0.5V, 100%=4.5V).
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Old 03-15-2012, 04:32 AM   #19
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amazing . Cant wait till you have it sorted, the ony thing that worries me about MS2 was no real knock control. I realise that its at minimum a required hardware upgrade but im sure the benifit and piece of mind will outweight the cost.

Congrats on the progress so far
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Old 03-15-2012, 09:00 AM   #20
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Quote:
Originally Posted by Reverant View Post
This is for the Enhanced MS2 that I build only. It is an integrated solution, there is an expansion board inside the case, much like the MS3X board, that has the knock solution on it. For the MS3, you need to get Jame's (jsmcortina on msextra.com) knock board. I would get this and install it for you, however he does not have any at the moment to sell.
Thanks. Does he have an ETA on them? Will he have them by the time you start my MS3X? I wouldn't mind waiting a bit longer for that.
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