Datalogging the Knock sensor?
#17
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When you say :
Which product of the link are you referring to exactly? (the stand alone?)
Originally Posted by NZ951
the Link records the knock values and can be plotted in a curve...
#19
Originally Posted by BoostGuy951
I'm sorry I didnt really follow this. Are you getting .2 volts when you knock on the block and then 0.0 volts otherwise?
I've got a knock display, but I also wanted to be able to datalog.
I've got a knock display, but I also wanted to be able to datalog.
#20
Originally Posted by hosrom_951
Claus: Did you have any logs on the knock sensor from Zeitronix but on various boost levels? maybe that would show some difference.
#21
Originally Posted by Dark Lightning
Does it seem accurate and useful?
I have it set so that there is a flash of light once or twice per lap. If that changes, then I know that there is something wrong. It is basically a reference. I don't know what severity of knock the DME uses to retard timing and reduce boost .
#22
Originally Posted by BoostGuy951
Yeah. I intend to give it a shot. I will report back as soon as I have a datalog with it as a variable. (which should be a while)
#23
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The knock-sensor is basically just a microphone. It's an analog device and puts out raw waveforms that must be massaged, filtered and interpreted. I've datalogged its output with a 'scope and it's not easy to detect knock visually from the screen. Stuff that you can hear from the Knock-Link doesn't show up distinctly in the traces. And I can't imagine what inaudible knock would look like.
If you take RMS average values of the voltage over time, it will increase linearly with RPM due to the louder engine noises (valves slamming shut, cam-lobes hitting lifters, etc.). Problem here is interpreting the knock waveform within all this noise. Knock's waveform and amplitude remains the same regardless of RPM and boost. So let's say it's a 0.2v spike rising from 0v in less than 2ms and rapidly diminishing in less than 1ms. If you set a voltage-level trigger at 0.2v, it will be "on" all the time after 4500-5000rpm because of all the other noise.
Also the main combustion waveform may take 20-30ms to rise from 0 and may reach only 0.05v at idle and small throttle-openings. But at 5000rpm under full-throttle/full-boost, the combustion waveforms will be 0.3v or higher with wavelets at 1/2 frequency for the valve-train. The problem here is that a voltage-level trigger will not catch a 0-0.2v spike mixed in with noise of 0-0.3v. You need an edge-trigger with a certain rise-rate that it's looking for. This appears to be a prime candidate for DSP technology.
Here's an application I've been examining for suitability for our cars: Intersil (HIP9010/11EVAL).pdf
If you take RMS average values of the voltage over time, it will increase linearly with RPM due to the louder engine noises (valves slamming shut, cam-lobes hitting lifters, etc.). Problem here is interpreting the knock waveform within all this noise. Knock's waveform and amplitude remains the same regardless of RPM and boost. So let's say it's a 0.2v spike rising from 0v in less than 2ms and rapidly diminishing in less than 1ms. If you set a voltage-level trigger at 0.2v, it will be "on" all the time after 4500-5000rpm because of all the other noise.
Also the main combustion waveform may take 20-30ms to rise from 0 and may reach only 0.05v at idle and small throttle-openings. But at 5000rpm under full-throttle/full-boost, the combustion waveforms will be 0.3v or higher with wavelets at 1/2 frequency for the valve-train. The problem here is that a voltage-level trigger will not catch a 0-0.2v spike mixed in with noise of 0-0.3v. You need an edge-trigger with a certain rise-rate that it's looking for. This appears to be a prime candidate for DSP technology.
Here's an application I've been examining for suitability for our cars: Intersil (HIP9010/11EVAL).pdf
#24
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I have a Link Knock Display. It has several little LEDs on it and one Large one that lights up to indicate knock. I'm wondering if I can solder my datalogging input wire into the circuit of the LED. I'm pretty sure the purpose of the circuit board inside the knock display is to massage and filter the signal. So I'll basically be datalogging when the Knock LED lights up.
#25
Originally Posted by BoostGuy951
I have a Link Knock Display. It has several little LEDs on it and one Large one that lights up to indicate knock. I'm wondering if I can solder my datalogging input wire into the circuit of the LED. I'm pretty sure the purpose of the circuit board inside the knock display is to massage and filter the signal. So I'll basically be datalogging when the Knock LED lights up.
#26
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I have used the Knocksense from Boris. It was on a modifed high CR 944NA.. We used a 951 knock sensor on the block connected to knocksense.. The device indicated some knock at high RPM, I'm not sure if it was engine noise or actual knock. We didn't hear actual knock...
The KLR has some interesting knock filtering algorithms.. Someone (guess who) has been asking me to show him how to log the signal after the KLR did the filtering (when KLR determines there is knock not noise). We figured a way how to log knock at the same time (RPM, AFR,..).
I think it'll be a good idea to compare the KLR knock detection with the Knocksense.. So SpecialTool, you'll have few toys to play with ..
Note: For those getting knocksense, make sure you tell Borris that it's for a Porsche as the wiring is different than his standard kit.
The KLR has some interesting knock filtering algorithms.. Someone (guess who) has been asking me to show him how to log the signal after the KLR did the filtering (when KLR determines there is knock not noise). We figured a way how to log knock at the same time (RPM, AFR,..).
I think it'll be a good idea to compare the KLR knock detection with the Knocksense.. So SpecialTool, you'll have few toys to play with ..
Note: For those getting knocksense, make sure you tell Borris that it's for a Porsche as the wiring is different than his standard kit.