J.P. Instruments EDM 960 Twin Pilots Guide - Manual (Page 32)

For Your Safe Flight Page 27
Expanded Leaning Procedures
Lean Of Peak mode: During the ‘lean of peak’ process, the EDM hunts for
the last cylinder to peak. This is because, ultimately, you want to have ALL
cylinders operating on the lean side of peak. You will final adjust your mixture
to this cylinder. To provide a unique graphical depiction during lean of peak
operation, the columns become inverted after the first EGT goes just below
peak. Each EGT column then originates from the top of the display and drops
downward. As each subsequent EGT goes past peak, its column will begin
falling. The columns length depicts how far the EGT has dropped below its
original peak. In this mode, each segment is 5° F. You will continue to lean
until the last EGT peaks
Leaning Turbocharged Engines: The leaning process for
turbocharged engines is by reference to the first EGT or TIT to reach
peak. Therefore you should use the Rich Of Peak mode. The factory
TIT red line may limit the leaning process, depending on flight
conditions. TIT red line is generally 1650°F to 1750°F. If TIT exceeds
red line (but not by more than 99°), the EDM will allow you to
continue leaning for one minute before a TIT alarm activates, implying
you should enrichen the mixture. NOTE: in some cases, TIT can read
approximately 100°F hotter than the hottest EGT. This is because of
unburned fuel in the exhaust igniting and is not necessarily abnormal
behavior. The reduced size of the JPI Hastaloy-X-tip probes produce
faster response and are more accurate than the massive factory
installed probes. Therefore a JPI probe may read as much as 100°F
higher than the factory installed probe. However, the certified factory-
installed gauge must be obeyed as the limiting factor when adjusting
your engine.
(note: never lean to the point where the engine is
running rough). When the last EGT peaks, its respective column will flash and
the word RICHEST appears. The scanner digital readout will now show the
current temperature difference from where peak EGT occurred and also the
current fuel flow. Note: if you hold the LF button, the display will show the
captured peak value of the ‘last EGT to peak’ and also the difference in fuel
flow between the first and last to peak (also known as the GAMI Spread). This
can be a good indication of how well your injectors are balanced (the smaller
the FF difference, the better the injector balance). Tapping STEP exits the lean
find mode and automatic scanning resumes.