Knock detection for MS2

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Knock detection for MS2

Postby Rod S » Wed Dec 04, 2013 7:28 am

Jean,

A long shot but I thought it's worth asking.

The DIYautotune board for MS3 looks very interesting but no good for MS2.

I assume it's microprocesser based (or is it a dedicated knock IC and the processing done by the MS3 CPU ?) and I guess from the panels in TS, it's James's work (or at least mostly his).

What about an (external) board that could interface with the IOx for MS2.

I can't see a good way of dealing with knock in MS2, apart from just building a circuit with basic bandwidth filters, but no relationship to engine timing (for dual sensors and valvetrain noise elimination), well no way that I've found yet anyway.

Rod.

(Edit - missed a bit)
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Re: Knock detection for MS2

Postby jbelanger » Wed Dec 04, 2013 12:14 pm

Rod,

The MS3 module is a specialised knock chip controlled by the MS3. The main issue with knock control on the MS2 is that it would require some way of finding the correct window for knock detection. So it either means that the MS2 has to use an output to signal it or the knock module has to have the full wheel decoder code.

I'll talk to James to see what he has to say.

Jean
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Re: Knock detection for MS2

Postby Rod S » Wed Dec 04, 2013 3:35 pm

Jean,

After a bit more reading after first posting I guess I realised the MS3 solution was using one of the specialised chips under MS3 control, so thanks for that clarification.

But can't the engine timing be read by the IOx over CAN - if there were to be an "external" solution for us MS2 users ?

I'm thinking either an add-on IOx board to solder the MS3 module to or a completely new IOx add-on board with the specialised chip as part of it.

Obviously any/all with James' support.

Rod.
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Re: Knock detection for MS2

Postby jbelanger » Wed Dec 04, 2013 3:55 pm

Rod,

The engine position can't be read over CAN due to the latency: that would represent an unpredictable delay due to any traffic on the bus which would mean the engine position would not be correct with no possible compensation. So that means the only way to get a knock window from the MS2 is through a dedicated output; it would be possible to combine that with the tacho output or rather use this as a tacho output because a window signal would pretty much be the same except for position and duty cycle. The knock signal could be read through CAN since there is enough time between 2 ignition events to send a CAN message.

The 2 options you mention are 2 possibilities I want to discuss with James. Another one is a complete and independent unit which would be based on the MS3 module and possibly the TinyIOx. That last one might be a better option for most because that would be usable in more setups (for example a Microsquirt). Of course that would not be the preferable option for current IOx/TinyIOx users.

Jean
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Re: Knock detection for MS2

Postby Rod S » Wed Dec 04, 2013 4:26 pm

Jean,

You've said many times before, in many different threads, that the CANbus isn't fast enough for accurate engine timing, I guess I'm surprised it needs to be that fast for timing a knock detection window. (how accurate does a knock detection window have to be ? but I guess that's another question, not really for this forum).

But still, I'll be interested to see what you and James can suggest (for MS2) given the CAN limitations.

Otherwise I'll just have to go for a bandpass filter and ignore timing.

Interesting discussion though.

Rod.
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Re: Knock detection for MS2

Postby jbelanger » Wed Dec 04, 2013 4:37 pm

Rod,

I honestly don't know how much accuracy the knock window requires. However, since the CAN bus latency is variable (and unpredictable) and the accuracy would vary with RPM I don't think using the CAN bus for triggering the knock window would be a good idea to get the best results. A stable window is probably quite useful in establishing a reliable noise threshold for a good knock detection. I think that noise rejection is rather critical for obtaining meaningful knock data.

I'll post here when I have some news from James.

Jean
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Re: Knock detection for MS2

Postby wes kiser » Thu Nov 13, 2014 10:23 am

The windowing basically has to be as fast and accurate as timing control, since it is tied to ignition events (IE, your window is so many degrees after an ignition event).
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