Variable Restrictiveness Exhaust

[Ord Millar]

-----Original Message-----
From: GARY <hobiegary at earthlink.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Saturday, May 15, 1999 1:13 PM
Subject: Re: Variable Restrictiveness Exhaust


<SNIP>


>3)
>I am trying to decide the best way to dampen the signal from my Knock
>Sensor (the Subaru). The resistance of the KS is 520K ohm.  The ECU
>appears to be sending about two to three volts D.C. to the Knock Sensor,
>but I don't know if that remains constant throughout operation.
>
>What do you guys think of a first resistor in series to dampen output
>along with a second resistor paralleling the seriesed KS and first
>resistor to make the overall resistance/impedance 520K ohm?  or using a
>diode to allow the D.C. monitor current to pass while offering
>resistance to the KS generated signal.  I thing a diode would filter the
>KS A.C. signal into D.C. and cause a problem.  Any other ideas?


First of all, isn't the KS a piezo sensor?  If so, I think DC resistance
doen't really matter.  If you want to attenuate, you could build a divider
around it - two resistors in series accross the element, leave one wire
connected to the KS, connect the other to the junction of the resistors.

If it is really damping that you want, instead of just attenuation, then you
need to build a low pass filter.