knock sensor
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[Freemantle]
Senior Member
H-Series, and I assume other Honda DOHC engines, naturaly ignore the knock sensor in open loop. If you are boosting in closed loop, then you have more problems than we have the capability to fix.
R.E.Developement
Import King of Irvington
but does the knock senser retard your timing 
[Freemantle]
Senior Member
Originally posted by R.E.Developement@Aug 17 2004, 08:33 AM
but does the knock senser retard your timing
[post=377932]Quoted post[/post]
And if they remained active past your secondaries/cross-over on a stock motor, you'd be in limp mode every time you got on it. The current system (as I understand it) is just a passive listening device through a bandpass sensor.
Meaning that lower frequencies are washed out and ignored, and it just hears the high one.
Standard engine noise is more than enough to constitute as knock through that sensor. A truley innovative knock sensor would be based on noise frequency, not loudness, and be timed with engine speed cylinder by cylinder. Nobody makes a knock sensor that extensive yet. I'd try to get in the Calculus of that, but I don't think that would benifit anyone here, and I'd probably screw it up anyway. Blundar (on my aim, radnulb on this forum) has looked into this subject deeply and is the person who actually introduced me to this idea.
fuck acoustic knock sensors. ion sensing is the way of the future, but that's another story. 
You got things minorly inverted freemantle - it does a bandpass filter in order to eliminate the frequency of noise associated with RPM. Above a threshold, bam - retard timing. It's primitive, but works acceptably for low RPM conditions where there isn't a lot of noise.
The problem with acoustic knock sensors is that engine noise increases more or less with the SQUARE of RPM, so your signal/noise ratio deteriorates to shit, even with filtering to focus on the frequencies you care most about. There are ways to get around this, but most of them involve Fourier transforms or other mathematical processes designed to turn the essentially "random" noise from the knock sensor into a series of frequencies with energy associated with them. The energy at a particular frequency is a much better indication of "knock" than anything.
If you start looking into ion sensing, you'll see that the data processing involved is still fairly complicated, but the upside is that there is essentially the same signal/noise ratio at 10000 RPM as 1000 RPM, which can't be said for any acoustical knock solution.
In stock form, the honda knock sensor is useless for anything except a tank of bad gas.
You got things minorly inverted freemantle - it does a bandpass filter in order to eliminate the frequency of noise associated with RPM. Above a threshold, bam - retard timing. It's primitive, but works acceptably for low RPM conditions where there isn't a lot of noise.
The problem with acoustic knock sensors is that engine noise increases more or less with the SQUARE of RPM, so your signal/noise ratio deteriorates to shit, even with filtering to focus on the frequencies you care most about. There are ways to get around this, but most of them involve Fourier transforms or other mathematical processes designed to turn the essentially "random" noise from the knock sensor into a series of frequencies with energy associated with them. The energy at a particular frequency is a much better indication of "knock" than anything.
If you start looking into ion sensing, you'll see that the data processing involved is still fairly complicated, but the upside is that there is essentially the same signal/noise ratio at 10000 RPM as 1000 RPM, which can't be said for any acoustical knock solution.
In stock form, the honda knock sensor is useless for anything except a tank of bad gas.
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