Richard004 hat geschrieben:ich werd mir das bei luepertz motorspor kaufen ist ja quasi bei mir um der ecke.
irgend wie versteh ich das mit der klopferkennung nicht. ich muß ja erst mal ne frequentz haben um zu sagen ob es klopf oder nicht.
(angeblich kann man das ja über den bohrungsdurchmesser berechnen. in meinem fall 8,4khz)
das diagram von der ks4 sieht jedenfalls schon plausibel aus.
Connecting Knock Sensor (Optional)
Tuning the knock sensor is not a trivial task, and can take a considerable amount if time and experimentation to get right. Configuring the knock dynamics of an engine and over comming issues of mechanical noise can take a lot of time and effort, therefore you must not rely on the knock sensor to prevent knock, this can only be done by sensible tuning and using the correct octane fuel for your application.
Although VEMS will work with a variety of knock sensors the ones that have been tried and tested are Bosch, although other 2 or three wire sensors may work. Do not use a single wire knock sensor as they use the common ground of the block to create the circuit, using the block will inject too much noise into the sensitive knock circuitry.
* EC18-pin3 Knock sensor signal (Bosch type pin1)
* EC18-pin2 Knock sensor ground (Bosch type pin2)
Some Bosch type sensors are 3 wire type, pin3 is the cable's shield. On either type of sensor the shield should be grounded near or on the engine block.
Configuring Knock Sensor
There are two areas to configure, the Sampling settings define the way that the signals from the knock sensor are treated. The Knock Control Action set the way that VEMS will behave when knock is detected.
Knock Sampling Settings
In the Extras->Knock sampling window, Enable and select the channel that you've connected the sensor to (the above wiring shows a connection to Channel 0).
Set Window Start to 12
Set Window length to 60
The knock window is best described using the following graph.
Knock is most likely to occur at the point when the cylinder reaches peak pressure. Assuming that your timing is correctly set up peak pressures will occur between 10-17deg ATDC. The knock window length can be specified between 0 and 60degrees, initially the window should be set to its longest setting but may need to be reduced to increase the accuracy of the detection.
The exact figures will vary depending on your engine's individual characteristics so you will need to tune the Knock Sensor's configuration to insure that you get the optimum function.
Set the Band-Pass Frequency (kHz) to the closest available frequency to the calculated knock frequency.
To calculate your engine's theoretical knock frequency we use the simpe equation: 900/(pi*r)
So using a 81mm bore we can calculate the following knock frequency: 900 / (3.141 * 40.5)
900 / 127.2105 = 7.074kHz
Select the maximum gain of 2. The Bosch sensor will never exceed 2volts (and it would take an explosion to do it), so there is no danger of overloading the sensor.
[dnb] You would never overload the sensor - the sensor produces a voltage proportional to vibration. The danger here is that the knock harware in VEMS either gets too small a signal so you don't see anything if the gain is too small, or if the gain is too big, then there is far too much signal and the output is always clamped at the rail voltage, so you can't distinguish knock from background noise. I do agree that 2 is a good number for the gain.
Select an intergrator time constant of 150uS The intergrator time constant denotes the speed that the VEMS fills its sample value, to fast (a low time value) and you will not get too short a sample, too long and you will not get enough sample data, we'll start tuning this when we set the noise level in the next section.
[dnb] Sampling is the wrong word for this really. The knock chip does sample data from the sensor but it then integrates (effectively performs a running average) it over the selected window. (Remember this window translates from crank degrees into a time period) The integrator time constant denotes the number of "bins" over which we want to calculate this average. If integrator time constant is too long then we get a small output because the average ramps up slowly, and if it is too short then we get a big output (and therefore possibly hitting the maximum value) because the average ramps up quickly.
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.
Knock Control Action
Now we've setup looked at the way VEMS identifies knock we can configure its actions when knock is detected.
In the Settings->Knock action window:
Testing Knock Sensor
You will need to use 'Det cans' or another method of listening to the engine so that you can hear the detonation events.
The first and simplest test is to ensure that the knock sensor and your det cans are all working.
In MegaTune go to Tuning->Spark Map and check that the Knock radio button is selected.
All activity from the knock sensor will be shown on the Knock Diff gauge.
Strike the engine block with a large spanner or wrench away from the and listen for a ringing sound, tests have shown that the bores will ring with the same frequency with this test as they will with detonation. If you hear the ringing sound check the Knock diff reading on the MegaTune window, if there is no reading check your electrical connections, and start to increase the Gain multiplier in the Extras->Knock Sampling Settings menu.