Knock sensors and knock detection
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Knock sensors and knock detection
I'd like to start a discussion on knock sensors and knock detection. I'm basically trying to tune a heavily modified 2.0l 4g63 and would like to be able to make some educated decisions as far as attenuating the knock filter maps.
What I've learned so far:
- Looks like the Evo knock sensor is a piezoelectric microphone
- Looks like the stock ECU knock filter maps use RPM and Load axis and are populated with Volts (presumably some kind of threshold for the 0-5 V signal from the knock sensor)
I've attached an Excel spreadsheet that contains the 12 knock filter maps from a stock 2003 ECU ROM, including a graph for each one.
What I'd like to determine:
- Why 12 knock filter maps? What condition(s) would determine the use of one map over another?
- What frequency is the stock knock sensor tuned to?
l8r)
What I've learned so far:
- Looks like the Evo knock sensor is a piezoelectric microphone
- Looks like the stock ECU knock filter maps use RPM and Load axis and are populated with Volts (presumably some kind of threshold for the 0-5 V signal from the knock sensor)
I've attached an Excel spreadsheet that contains the 12 knock filter maps from a stock 2003 ECU ROM, including a graph for each one.
What I'd like to determine:
- Why 12 knock filter maps? What condition(s) would determine the use of one map over another?
- What frequency is the stock knock sensor tuned to?
l8r)
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Originally Posted by Ludikraut
- What frequency is the stock knock sensor tuned to?
l8r)
l8r)
There are also various resonant modes the knocking can take on. This image shows most of the modes for a typical pent-roof combustion chamber:
Lots more information here: http://www.vehicular.isy.liu.se/Publ...PhD_580_LE.pdf
And here: http://www.vehicular.isy.liu.se/Publ...LIC_962_IA.pdf
(carefull look at the Yoshiyama-Tomita model, if Ion-current modelling is your bag)
Also, feel free to search the old NACA (aka NASA) archives for "engine knock" or "detonation" here: http://naca.larc.nasa.gov/
Lots of good documents there. TR912 is of particular interest. In either case, whole buttloads of good information on knock both in general and in specific. Lots of high-speed Schliren photography of knock, interesting conclusions and unusual methods. It's old, but interesting notwithstanding.
-Adrian
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