I am sure that the noise is still there, but now it does not interrupt proper reading of the RPM. So, the coil drivers and injector drivers can do what they are supposed to. Here is my explanation of it:



All the VR input circuit cares about is when the signal crosses the cross-over point you set with R56. For the VR sensor, that is set to zero. As the VR sensors magnet passes over a steel tooth of the crankshaft, the output will smoothly swing from negative to positive. The hall sensor output is the same general shape waveform. It is just shifted up by a couple volts and changes sharply from 0 volts to 5 volts as it passes over a notch in the crankshaft. Since all the VR input circuit cares about is when the signal crosses the cross-over point, the number of cycles per time (to calculate RPM) is the same. Because of this, noise and spikes are meaningless. It doesn't matter how high the output goes, as long as it hits the cross-over point at the right time. The R52 potentiometer sets the hysteresis. As I see it, that adds an additional constraint. Not only does the signal have to cross the cross-over point, but it has to hit a certain amplitude before it is registered. That allows the circuit to ignore noisy outputs that dance around the cross-over point. This is my simplified understanding. Nate can correct me on whatever I got wrong.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire