- Mon Jun 22, 2020 3:02 am
As we have established these are non-typical applications for common modules, and I have hopefully impressed users to first look at the entire package for best solutions; while modding the modules is not suggested, they can be minimally modified to "tune" signal performance for specific applications and hardware components. Modding simple I/O resistors have specific consequences, and changes should not be attempted without good understanding of goals and multiple effects and results. Modifications are always compromises.
With that said and for those desiring to tweak their signal performance for specific applications, the input and output resistors may be changed-out or piggybacked (stacked parallel resistors). The DSC may be treated as two separate signal processors, Channel 1 and Channel 2. This is important, as the ECM board filters are often of different values for crank and cam circuits, and must be tuned independently. As shown on your supplier's site, the Trigger Edge setting should be Falling, and VR sensor output polarity should be correct (approaching edge going high).
Tuning the DSC I/O:
In the image below, resistors are marked for input stage (IN1 and IN2) and output pullups (OUT1 and OUT2). Outputs should be tuned first in most cases. All tuning should be on the ECM, with the sensors and other components to be used when installed. Testing or re-testing under cranking and running conditions is strongly recommended in order to also tune for system noise as a strong factor. If there was no system noise, we could use an unfiltered perfect square wave, and no need for tuning. But all systems have noise. A square signal is not important, as Speeduino only reads one edge. A usable signal with clean falling edge and without noise is important.
Output resistors are simple pullups, and affect the output signal rise time and voltage, primarily affecting high-RPM. The DSC does NOT have any output capacitors, and output signal is most affected by ECM circuit filter capacitors. For this reason, the DSC output resistors have changed value in various versions as ECMs have changed filter capacitors. For faster rise time and higher high-RPM voltage peak, reduce the OUT resistor value incrementally. Alternatively, or simultaneously, reduce the ECM filter capacitor value. Excessive reduction of either alone may result in excessive noise (EMI) and lost signal or lost sync.
Input resistors are NOT shunt resistors, and are to regulate the input signal current to the input stage circuit. Input resistors are balanced to permit minimum-RPM signal response, while preventing over-driven signals at high-RPM. Generally, the input resistors are tuned as high-value as possible to prevent signal over-drive (loss of signal at high-RPM), without raising minimum RPM sensing (cranking) threshold above minimum low-battery cranking or ECM detection speed.
-= If it was easy, everyone would do it =-