J.P. Instruments EDM 760 Pilots Guide - Manual (Page 31)

If your installation includes a separate panel mounted alarm warning
enunciator light or audible warning, it too will be activated.
There is no alarm for the individual EGTs because the temperature values
can assume different ranges depending on the flight configuration (run up,
climb, cruise). There is an alarm on the DIF measurement, the difference
between the hottest and coolest EGTs. DIF—or span—is the important
measurement for monitoring the EGTs. See “Factory Set Default Limits”
on page 43 for a list of the alarms and their factory default settings.
When an alarm is displayed, tapping the STEP button will temporarily
disable the alarm indication for the next ten minutes.
When an alarm is displayed, holding the STEP button until the word
OFF appears will disable that alarm indication for the remainder of the
flight. See Alarm Limits” on page 43.
Alarm Priority
If multiple alarms occur simultaneously, the higher priority alarm will
temporarily “hide” 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 TIT TIT over temperature
CHT CHT over temperature
OIL OIL temperature
CLD CHT cooling rate
DIF EGT span
BAT Battery voltage
LO FUEL Fuel remaining low
Lowest priority LO TIME Fuel endurance low
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.
For Your Safe Flight Page 27