y8s

iTrader: (8)

Since my settings were requested by a couple people, I thought I'd start this.

I pulled some of the settings from msextra. I derived my own value for bandpass frequency based on something. I think it was either a formula Jason C posted or somewhere found on the internet.

Integrator time constant is the default I think.

Scaling is simply based on what range I thought "noise" looked appropriate. What I interpret as "obvious knock" are spikes at least 2-3x times taller than the "noise" in the chart at the end.

Car: 2001 Miata NB
Sensor: Stock 2001 miata NB sensor
Setup: big turbo, motor internals and head are stock .





I have not really touched the following values:





And those settings result in this:

soviet

iTrader: (10)

A+ would read again.

Reverant

iTrader: (10)

y8s, is your rev limit 8000rpm?

y8s

iTrader: (8)

nope, but I like to tune above my rev limit because I don't like ambiguity

Reverant

iTrader: (10)

Your log shows 8000rpm and 200kPa max.

y8s

iTrader: (8)

Oh that. I set the maximums to round numbers or numbers that make the 50% line meaningful (for AFR the dotted line is 14.7). Note also my TPS goes to 101. And volume to 11.

I find that having the graph trace sit right up against the edge of the graph limits makes it hard to read.

Reverant

iTrader: (10)

So how much noise do you get at peak RPM/boost? I am getting a lot of noise after 5500rpm or so.

y8s

iTrader: (8)

a lot.

I haven't really spent much time tweaking on this thing. I suspect some improvement could be had by actually doing something with the windowing but... I haven't driven my car more than about 50 miles in the last month or two.

Here's a random example. I haven't decided if I should call these moderate spikes "noise" or "knock" or neither. I think the way to go would be to get a passenger with det cans and a computer to mark the logs as soon as he heard something and then match up the spike levels with the marks and adjust based on that.



Similarly, spending 5 minutes to look at the window settings and make some educated guesses where knock occurs in our motors would be good.

miatauser884

iTrader: (11)

How are you detecting individual cylinder knock? Is this just a setting that is listening for different frequencies that is cylinder dependent? I see the per cylinder settings, but what is the gain, and why are they all the same?

EDIT:

I'm an idiot, it would just be based on rpm and the time window in which the vibration is detected.

Is the gain supposed to be a factor that takes into account the latency of sound traveling through the block for the different cylinder distances? i.e. the furthest cylinder would need a higher gain so that the amplitude of the peak is the same as the amplitude of a peak in the closest cylinder for a knock event of the same magnitude???

y8s

iTrader: (8)

I think the gain is simply a linear scaler.

and yes, the individual knock is derived from the window relative to the spark for that cylinder.

Reverant

iTrader: (10)

I can tell you right here and now that det cans are useless above a certain RPM due to noise. I just can't listen ANYTHING above 6000rpm on all B6/BP engines that I've tuned so far, built or stock. So no wonder the knock sensor readings spike above that.

richyvrlimited

iTrader: (1)

Please excuse my naivety if this is stupid...

BUT, does it matter? if AFR's are good and timing is static from that point to redline, and you're not knocking at 6000rpm, then you really won't be at 6500/7000 rpm due to the higher piston speed?

Reverant

iTrader: (10)

Depends on the timing map. I generally add more timing as engine speed increases to hit the ~17* ATDC sweet spot, so there is the probability of knocking above 6000rpm. Also between 5500 and 6000rpm it is also quite noisy, so listening for knock there is not exactly easy either.

richyvrlimited

iTrader: (1)

17deg ATDC sweet spot? What's that

Do you mean BTDC?

Fair point on the increasing timing. I do the same, but not by a particularly large amount, to be honest it may as-well be flat it's that slight an increase...

Reverant

iTrader: (10)

Our engines will produce the most torque when cylinder peak pressure happens around 17* ATDC.

richyvrlimited

iTrader: (1)

Ahh, I thought you were saying the goal was to hit ignition at 17BTDC :-)

miatauser884

iTrader: (11)

How fast does combustion usually occur in our engines? Im trying to figure out how to calculate a timing value for a given rpm that yields the 17 degrees atdc.

richyvrlimited

iTrader: (1)

There's no answer to that, it depends on AFR used (richer burns slower), fuel, injector type etc etc.

Reverant

iTrader: (10)

Exactly.

y8s

iTrader: (8)

Ultimately though I suspect nobody is knocking above 6000 rpm much. you can probably just set your thresholds relatively high and go back to your normal day.