Good morning, I can’t configure the knock noise.
I have a log with a relatively low ignition advance (e85).
I have the 4 cylinders assigned to the same knock sensor but they give me different readings, I can’t find an explanation.
thanks very much
log hoy.emublog3 (667.9 KB)
Despite only having a single sensor, it’s possible to determine cylinder specific knock levels by reading the knock sensor only during the part of the engine cycle where knock can actually happen for each cylinder. For example, around the time an ignition event may begin on cylinder one, the ECU will “listen” to the sensor, process the data, and the resultant value will be counted as cylinder 1s knock level. Then, the process repeats for the next cylinder in the firing order, and so on.
By windowing like this, the signal to noise ratio can be greatly increased - and with knock detection, noise is the enemy.
However, depending on the position of the knock sensor (or sensors), the design of the engine, and countless other factors, it’s necessary to give you a gain control for each cylinders knock values, so they can be normalized. This way, a knock event of a given severity will result in the same value regardless of cylinder, so that a common knock noise level table can be used. Even the engines own background noise may vary substantially throughout the cycle, which is why even in a no knock case, the values may be substantially different themselves.
But, like the knock detection tuning on any ECU, it’s extremely tedious and requires expensive equipment such as in cylinder pressure transducers to tune it properly as an OEM would. You probably won’t get a perfect result with any equipment short of that, but you can likely get it good enough for most use cases with a set of knock ears/det cans.