Knock senzor configuration

[MWfire]

I have knock senzor on my opel 2.0i(86mm bore).
I connect one senzor to two channell(one is 6.64kHz and other 15.84kHz).
I set window lenght to 60(R is about 133).
But i don't have a clue how set knock action treshhold and noise scale faktor.
When i loock my log, i can see konck dif value 0.8 to 1.5 and two time in minute about
30. One time it was 340.
How can i decide knock action treshhold?

[dnb]

This is a VERY difficult question.  I'm looking at it now on my car, but I haven't got a decent answer yet.

I have modified my Megatune to log raw data from the knock sensor to see if that tells me something that "knock diff" doesn't tell me. 

I really need to get the car on a rolling road so I can make it knock in a controlled way and see what the sensor readings do.  This should be happening this month (depending on work commitments) 

[multiplex]

what did you have to do to log the raw value?

thanks.

[dnb]

It was a "simple" change to the VEMSv3.ini file in the MT2.xx directory.

I will post up exactly what it is after work.

[MWfire]

dnb can you post?
Tnx.

[MWfire]

It is easy to log knock value. Just on end in vemsv3.ini(megatune2.25/mtcfg/vemsv3.ini) add this.
   entry = knock_cyl_0_knock_val,   "knockvalue", int, "%d"   
   entry = knock_cyl_0_noise_val,   "knocknoise", int, "%d"
Or you can make to see in megatu in Realtime display. Now i can see D and R value
when my car is knocking. How to relate D and R to knock action treshhold,noise scale factor?
Or i just change this value to get knock detectionflag?

[rob@vems.co.uk]

Here's what I've written in the UserGuide

Setting the noise level

VEMS has Knock values on page 5, so using your termial program type Manmlp05 to switch to the output screen, and mll to see the values:

adv:+25 dwell:313   
S:02DA L:00ED C:0CF9
D:0049 00 05 d: +002
R:004C ka:00 00 00 

The Values that you are interested in are:

D: xxxx is the signal in the Knock Window Phase, which shows us the noise level where knock is likely to occur.

R: xxxx is the signal value in the noise phase, the noise phase is where knock cannot happen.

The maximum value of D or R is 3FF, we suggest that you tune for a 1/3 of this value to be noise, to set this you will need to drive the car without it knocking and set the noise value to a value averaging 131 to 133. You shouldn't see too much of a difference between D & R at this stage, measurements have shown that the values are around 1.1 to 1.2 times the D value: 14F to 170.

Starting value is Manmttg99c0F To increase the intergrator time constant reduce the number OE to 00, and vice versa to decrease 10 to 1F.

Type mll to see the D & R values after each constant change. Tune the sensor until your R value reads 305 to 307 with normal driving.

Finally type mcs to save, and byebye to take VEMS out of its 'terminal' mode.

If you start to tune your knock window length you may need to reduce your Intergrator Time Constant to increase the signal level.

The full knock setup is in the UserGuide:
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPhatBob%2FUserGuide

[Sprocket]

Looking at the knock sampling menu, there is an option labled 'channel' with two options '0' and '1' What is this actual cofigurable point? there are two knock detection input channels. If i have only one sensor I understand to configure the 'channel' to '0', but what iff I have two sensors, would i configure 'channel' to '1' and the firmware then samples both sensors?

In the same menu, where does the 'channel 1' and 'channel 2' come into this? is this the two channels, and if only channel '0' is configured it uses 'channel 1' bandpass filter settings?

Also what would be good reasonable knock action values to be getting started with.

I have said it http://www.vems.co.uk/forum/index.php?topic=126.0 as have others, the user guide is incomplete in this respect and does not describe these configurable points, and its not in the VEMS manual in the wiki

Im looking at this where it says to configure the second channnel for the higher frequencies and increasing the gain to better detect knock, or is this information dead in the water?

http://www.vems.hu/wiki/index.php?page=DetonationDetection

[rob@vems.co.uk]

Looking at the knock sampling menu, there is an option labled 'channel' with two options '0' and '1' What is this actual cofigurable point? there are two knock detection input channels. If i have only one sensor I understand to configure the 'channel' to '0', but what iff I have two sensors, would i configure 'channel' to '1' and the firmware then samples both sensors?

Its not clear as the drop down should say "Channel 1" and "Channel 1 & 2"

In the same menu, where does the 'channel 1' and 'channel 2' come into this? is this the two channels, and if only channel '0' is configured it uses 'channel 1' bandpass filter settings?

Also what would be good reasonable knock action values to be getting started with.

I think the above answer should make that channels clear.

knock_max_retard    12 
knock_default_retard 4
knock_retard_step    2
knock_retard_delay    0
knock_advance_step    2
knock_advance_delay   15
knock_minrpm          1500 (just off idle)
knock_maxrpm          7500 (or what ever your red-line is)

I have said it http://www.vems.co.uk/forum/index.php?topic=126.0 as have others, the user guide is incomplete in this respect and does not describe these configurable points, and its not in the VEMS manual in the wiki

Well as soon as someone comes up with a clear and simple method of tuning this feature I'll happily write it up.

Im looking at this where it says to configure the second channnel for the higher frequencies and increasing the gain to better detect knock, or is this information dead in the water?

http://www.vems.hu/wiki/index.php?page=DetonationDetection

Nope, there have been no changes in the rules of harmonics, but its only a suggestion for experiementation purposes, the whole feature should be regarded as experimental because knock detection is a huge and complex subject.

[GintsK]

Question about using 2 sensors is actual for me too. Many engines have two.
Last week we got running '99 M3 engine. And there are even 3 sensors. This engine like to knock CR=11.5. And I will be happy if configuring two of them for use.

Gints

[rob@vems.co.uk]

V engines tend to have one sensor on each bank, 6 cylinder engines have one per 3 cylinders.
With these engines you would go for the same frequency for both sensors, although having spoken to Cliff about this I would say that the 2nd harmonic frequency would be the best to use because you're less likely to get mechanical noises causing false triggers.

[Sprocket]

Thanks Rob,it was as i thought, just reinforcing my thoughts.

I understand the theory of the knock action, but its the meanings of the 'values'. It would be nice to know the real meanings of these values and how it relates to the knock action strategy, that way i would be able to tune it? Im not after numbers really more of an understanding of what its asking i supose. As we have seen above, everything is not as it would appear

I would suggest that some values could be used as a generic start point such as retard values and then tuned from there, as it stands everything is set to zero.

LOL, im sure i read something in the MegaManual on knock action, might have a lookie over there

[rob@vems.co.uk]

I'm not sure what you mean by the values, the ones I wrote were some starters

knock_max_retard    12 (12 deg maximum retard)
knock_default_retard 4 (4 deg the first time knock is heard)
knock_retard_step    2 (2 deg steps at a time if knock is still heard)
knock_retard_delay    0 (0ms - don't wait to do it, do it now!)
knock_advance_step    2 (2 deg steps advanced at a time after
knock_advance_delay   15 (wait 15ms before it starts to return the advance)
knock_minrpm          1500 (just off idle)
knock_maxrpm          7500 (or what ever your red-line is)

The other values have no rule of thumb values.

[Sprocket]

knock_max_retard    12 (12 deg maximum retard)
knock_default_retard 4 (4 deg the first time knock is heard)
knock_retard_step    2 (2 deg steps at a time if knock is still heard)
knock_retard_delay    0 (0ms - don't wait to do it, do it now!)
knock_advance_step    2 (2 deg steps advanced at a time after
knock_advance_delay   15 (wait 15ms before it starts to return the advance)
knock_minrpm          1500 (just off idle)
knock_maxrpm          7500 (or what ever your red-line is)

Perfic

Exactly what i was after

Thank you, i am now a happy man

[Sprocket]

Thinking about this now, would it be slightly better to set the retard step to 4 as well as the default retard, that way, if knock is heard after the default retard, it will retard another 4, then advance 2.

Is it not better to jump out of and then approach knock rather than step out of it? that way the jump back is a safer step? If you retard 4 and its still knocking, id rather retard another 4 and get clear of it

Remembering of course, knock detection is a protection rather than a control

Just some open thought