Nissan Timing Wheels
Having looked at the Nissan Silvia and 200SX models (S12, S13 and S14) they all use a cam driven timing wheel with a speed sensor of 2degree resolution and portals of different sizes to denote the current cylinder.
The two degree marks would cause too much time to be spent servicing the interrupts, and as the sensor is cam driven we need only a missing tooth to tell us which cylinder is which, so a simple 36-1 image could be made:
And using another_trigger_tooth of 0x09 would provide a trigger event for each cylinder.