J.P. Instruments EDM 740 Pilots Guide - Manual (Page 36)

Page 36 Engine Data Management
When an alarm is displayed, tapping the STEP button will temporarily
disable the alarm digital indication for the next ten minutes.
When an alarm is displayed, holding the STEP button until the word
OFF
appears will disable that alarm digital indication for the remainder of the
flight. See ‘Factory Limits and GPS’ section on page 52 for a list of the
alarms and their factory default settings.
Alarm Priority
If multiple alarms occur simultaneously, the higher priority alarm will
temporarily “mask” the lower priority alarm(s). When an alarm occurs,
note the cause of the alarm and tap the STEP button to clear the alarm
indication so that you will be notified of any other alarm that might have
occurred. The alarm priorities are as follows:
Highest priority CHT High CHT
OIL High OIL temperature
TIT High TIT
OIL Low OIL temperature
CLD Excessive CHT cooling rate
DIF Excessive EGT span
BAT High battery voltage
BAT Low battery voltage
MAP Overboost Manifold pressure
O-P Oil pressure
LO REM Low fuel quantity remaining
LO H:M Low fuel endurance remaining
Lowest priority FF Low fuel flow
Pre-Ignition and Detonation
Combustion that is too rapid leads to detonation and possibly pre-
ignition. Detonation is abnormally rapid combustion where the fuel-air
mixture explodes instead of burning uniformly. It causes the EGT to
decrease and the CHT to increase, and can appear during the leaning
process. It occurs under high compression from fuel with too low an
octane rating, or from avgas contaminated by jet fuel. Fuel additives,
such as lead, boost the octane rating and slow down the combustion
process, producing an even pressure to the piston.