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Old 12-18-2013, 10:43 AM   #1
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Default Knock sensor never goes above 20% - Normal?

Megasquirt 3x, knock board, stock sensor. Boosted.

Configured per the instructions on MSextra, and looks similar to what I have seen on other installs here.

Only problem(?) is that I never go above 20% knock. That worries me because I have seen other people here that see numbers creep up past 60%.

I have a conservative spark tune and I know I am leaving a lot on the table, but I wonder if my settings or setup is wrong. When I get home and am in front of my tuning laptop I will post my settings and a sample log file, but for the time being is it normal for knock sensor readings to sit in the single digits during normal operation and only creep up to 20 or so?

I don't have det cans to verify or listen. Another friend recommended intentionally messing with timing to cause a moment of knock (at idle for example) to verify but that sounds risky.

Thoughts?
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Old 12-18-2013, 10:46 AM   #2
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That sounds idiotic. You shouldn't rely on the stock sensor and ms to fine tune spark anyways, its more to prevent massive failure should you suddenly get a ton of knock. IMO its not developed/advanced enough to rely on like when tuning an OEM ecu or the higher end systems.
Fine tuning should still be done with det cans IMO.

*edit: if you really wanted to make it sharper (and/or noisier) you can just open it up and turn up the pot for the knock sensor. But be aware that you can make it way too sensitive and it will just pull timing all the time basically
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Old 12-18-2013, 12:36 PM   #3
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We aren't planning on tuning off of the knock sensor, I am just concerned that it's not doing it's job if it's reading so low.

You say open it up and turn the pot. I didn't notice a potentiometer on the board and I dont see one here:
Megasquirt-3 MS3 - knock module

Am I missing something?
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Old 12-18-2013, 01:48 PM   #4
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hmm I don't know how its set up on the ms3. on my ms2e there was specifically a "knock sensor sensitivity" pot

Perhaps the MS guru's can chime in
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Old 12-18-2013, 03:28 PM   #5
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It's all done in the software, assuming the signal isn't a flatline, which would indicate a sensor or wiring or knock module fault, then just adjust the gain in the knock sensor settings page.

Then look into tuning the knock window

You can also adjust when to ignore the signal. IME above peak torque the OEM MK2.5 sensor gets swamped by background engine noise. I really need to try a resonant sensor instead.
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