MoTeC M84 - Manual (Page 20)

18 Installation MoTeC
Trigger Sensors (REF & SYNC)
The trigger sensors supply the necessary timing information to the ECU so
that it knows when to fire the fuel injectors and ignition system. Normally two
sensors are used, REF and SYNC.
Many different types of trigger sensors and chopper patterns may be used.
The wiring and ECU setup information for the trigger sensors are specific to
the particular system. Refer to the appropriate MoTeC drawing.
Home made sensor systems often cause problems. Do not use Chrome molly
for chopper disks as it is a non magnetic material. Runout of the disk,
imperfections and bolt heads are also potential sources of problems. Where
possible it is best to use the manufacturer’s trigger system.
REF Sensor
Supplies the crank position information.
Some sensors supply one pulse per Top Dead Centre (4 pulses per engine
rev on a V8), others supply as many as 360 pulses per engine revolution.
The Engine RPM is derived directly from this signal.
SYNC Sensor
Used to indicate each engine cycle, which is required for sequential injection
and multicoil operation.
Generally supplies one pulse per engine cycle (i.e. once every 2 revs on a 4
stroke engine).
On some special trigger systems the ECU can be synchronised using the
REF sensor only (e.g. Ford Narrow Tooth)
REF / SYNC Alignment
Most modern distributors supply both REF and SYNC signals in which case
the alignment is pre-set.
When using separate REF and SYNC sensors the alignment of the two
sensors relative to one another is critical. Ensure that the sensors are aligned
correctly for the type of trigger system being used. Refer to the appropriate
drawing. Allow for any mechanical play in the distributor drive system if the
SYNC signal is derived from the distributor.