J.P. Instruments EDM 700/800/711 Pilots Guide - Manual (Page 29)

For Your Safe Flight Page 25
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 “Alarm Limits” on page 41.
EDM-711 primary alarm display lamps cannot be disabled.
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
LO FUEL Low fuel quantity remaining
Lowest priority LO TIME Low fuel endurance remaining
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.
Pre-ignition is caused by hot spots in the cylinder. Ignition occurs prior
to the spark plug firing. The EDM depicts pre-ignition as a sudden red
line of the EGT on the analog display. This may occur in one or more
cylinders. The affected cylinder column(s) will flash while the digital
display will show an EGT higher than 2000°F. At this temperature