Rotor/Reluctor Phasing Question

There are likely a differences in VR interfaces, comparing GM to Mopar. The trigger level varies some with the VR sensor resistance. It is a component of the bias circuit for the VR sensing interface. The tolerance in the VR sensor (pickup coil) resistance is typically large, so timing varies some with particular sensors. Also the sensor technology is different between GM and Mopar, while there are similarities, the interface may not be optimized.

I use a specialized VR interface chip and optimize circuit resistor values to match VR sensor to optimize sensor performance. At the present time I do not have a GM nor Mopar box for comparison. VR sensing technology at best is not perfect, it is cheap and common.

I like Hall gear tooth sensing better. Hall sensing with magnets varies with magnet irregularities. Example Pertronics. Huge efforts to match individual magnet strength and position for consistent trigger..

With correct phase of the pickup, the trigger occurs in the level above the zero transition where the signal rapidly changes from - to +. Because the transition slope is great, the timing variation will be slight, however it will vary some with RPM. It varies with RPM because the VR signal increases with RPM and the changes slightly the trigger point because the trigger threshold is a fixed voltage, not position. Timing will advance slightly with RPM due to the VR sensing.

When the VR pickup is incorrectly wired, the trigger point happens between the reluctor teeth, not half way, but at the threshold. Because the transition is slow (flux is nearly constant) the trigger point will be inconsistent. It will be based greatly on noise, RPM, and mechanical variations. The rotor phase is off enough for significant problems in spark distribution.

I tried to use MS Paint to copy and flip the VR signal in my post, then add the change in trigger point based on the thresholds. I ended up with a mess, so did not want to post. Some might be able to do the mental recreation, and visualize the timing and hysteresis differences with flipped signal. The hysteresis related time significantly increases, this may also result in undesirable change in dwell control, and might rev limit. Hysteresis is the the negative change from the trigger lever, that resets the trigger output.