User guide

F10X Manual
112
E.4 Trigger Edge
The ECU uses the signal transitions from low to high called rising edges and high to low
called falling edges to determine engine position. In most instances the ECU will only uses
one type of transition (rising or falling) for a trigger and this is known as the Trigger Edge.
It is only the position of the triggering edge that is of importance.
Some trigger devices may have uneven pulse widths to indicate the position of a specific
cylinder (often cylinder 1). If this edge was used as the trigger edge then there would be a
variation between the trigger position for cylinder 1 and all other cylinders. This would lead
to unstable RPM and ECU operation. To ensure even injection timing and RPM the trigger
edge in this case would need to be changed.
As shown above, the Rising edge of the pulse for cylinder number one occurs 20 degrees
before the Rising edge pulse for all other cylinders, but the Falling edge occurs at the same
position, regardless of cylinder. In this case the Trigger edge would need to be set to Falling
in the Trigger Setup page.
Falling Edge
Rising Edge