J.P. Instruments EDM 900 Pilots Guide - Manual (Page 30)

Page 30 Engine Data Management
Leaning Lean Of Peak (LOP) Detection: Note: This mode should
only be used when your engine is equipped with balanced fuel injectors
or you have a DIF value of around 80 degrees. When using the Lean of
Peak mode, you lean until all EGTs decrease slightly below their
respective peaks. The EDM has automatic peak detection and will
sequentially indicate leaning progress. When the first EGT peaks, the
word LEANEST appears and the cylinder I.D. box highlights the cylinder
number. Each column successively drops as leaning continues. When
the last column drops (last EGT peaks), RICHEST appears and its
respective column flashes momentarily. The last EGT to peak is the one
you will use when setting the final mixture.
Finalizing the Lean Of Peak Mixture: The Scanner® Information
Area displays the degrees below peak for the last (or richest) EGT to
peak, giving you precise information necessary in setting the final
mixture. Adjust the mixture to achieve the desired value below peak
(using the digital EGT readout) or before engine roughness occurs.
Caution: do not lean to the point where the engine runs rough. Note: the
peak EGT value encountered during leaning can be recalled by holding
the PEAK button. Do not exit until finished or all values will be lost.
Tapping STEP exits the lean find mode and automatic scanning
resumes.
Peak Detected - Lean Of Peak Mode LOP