An old popular
misconception that other manufacturers
of EGT's is that it is not necessary
to know the exact exhaust gas temperatures.
However, if you have read recent
reports, shock cooling can be catastrophic!
The EDM alerts the pilot of those
conditions which are most vital
to the maintenance of well performing
engine. The value in measuring EGT
not only lies in finding the ideal
ratio of fuel to air that results
in complete combustion, but in Long
Term Trend Monitoring.
Trend monitoring
will identify those nagging little
problems before they turn into
serious problems. It is the most
important tool for diagnosing
engine problems, and it works!
Digital displays make all the
difference obvious. Trend monitoring
is simply not possible with just
a bar graph indicator. Yet, with
only a digital indicator, quick
glance temperature recognition
is not possible either. With a
digital display, engine data can
be recorded by the pilot in a
log book on a monthly basis. EGT
and CHT will group themselves
into a tight pattern at specific
MAP & RPM. As a problem begins
to develop in one or more cylinders,
the EGT span will start to enlarge.
The DIFF mode "dot" will identify
the problem cylinder causing the
large span. Factory new injected
engines have a typical span of
80ºF, carburated 140ºF.
The EDM-700 identifies
the optimum mixture accurately
and automatically. After cruise
power has been established, the
pilot just presses the function
button of the LEANFIND "LF" mode.
As the pilot begins to lean the
mixture, the EDM-700 is checking
all cylinders, using a proprietary
algorithm looking for the first
cylinder to achieve peak EGT.
"PEAK EGT" will be displayed when
the first cylinder to peak is
detected. The display will also
then flash the cylinder column
and show peak EGT. The pilot has
the option to increase (the richness
of the mixture) or operate at
peak. Leaning faster than the
engine can respond will cause
the display to flash "2 FAST."
The EDM is monitoring all alarms
in the background and if the TIT
limit is exceeded during the Lean
Find process, the TIT column will
flash first. Some turbocharged
engines do peak TIT before the
EGT peaks.
Since 1995, pre-ignition and
detonation have become more prevalent
with the new fuels available.
Therefore it is of the utmost
importance to monitor ALL EGT's
at one time during climbing, and
leaning. Pre-ignition once started,
causes an extreme temperature
rise and is self sustaining until
engine failure occurs, which can
be in less than one minute. Pre-ignition
will cause the EDM's bar graph
to reach maximum height on that
cylinder. Seeing all cylinders
at once will permit the immediate
action required by the pilot.
For example, a
Beech Bonanza with an 0-470 engine
at 10,000 ft. @ 65% power and
fuel at $2.20 per gal. At a true
airspeed of 160 mph and a peak
EGT, this engine consumes 11 gph.
This means that in 500 hours,
the Bonanza will consume $12,000
in fuel.
Most pilots not knowing which
cylinder peaks first, operate
at a 75 to 100 degrees rich of
peak. Too rich of a condition
causes vibration and carbon deposits
in the engine. Flying under such
conditions, a very rich mixture
would result in an increase airspeed
of 2 mph, while the fuel burned
would increase by 2.2 gph. If
the EDM was used to lean the engine
only 10 degrees rich of the peak,
the plane would cost 20% less
to operate or $2420.
A complete engine
data recording system. Capable
of recording not only EGT and
CHT as some less sophisticated
systems do, but also can record
all 24 engine temperatures, plus
all engine pressures, RPM and
can calculate percent of horsepower.
The ability to print out alarm
conditions, with three dimensional
color data analysis of your computer,
is also a feature.
Diagnosing
an engine problem is a very complex
task, requiring the data from
several engine instruments. Recording
EGT & TIT temperatures is
only the start. In order to fully
understand the engine, RPM, MAP,
OIL TEMP., are also required.
This is why you should not be
misled my less sophisticated copies
that claim data recording capabilities.
These gauges simply don't record
the necessary information to make
a thorough engine problem diagnosis.
For example, a large drop in EGT
could be a serious problem developing
or just the addition of full throttle.
JPI realized this at the beginning
of the development of its EDM
data recorder.
Precise
manifold air pressure is required
to measure accurate engine power
levels. The EDM's precision solid
state transducers measure MAP
to an accuracy of 1/10 inch of
Hg. Rpm is measured within one
RPM as well. As a pilot, you know,
it takes both RPM and MAP to calculate
Percent of Horsepower. Both are
recorded with the EDM.
JPI's proprietary
algorithm calculates and displays
percent of horsepower from carburated,
normally aspirated, high performance
injected, turbocharged and inter
cooled engines. Try taking off
from a high density altitude airport
by setting maximum HP before releasing
the brakes.
The EDM-700 Data recording model
automatically records as many
as 36 engine temperatures and
4 pressures, recording one set
of readings every second, hour
or however you program its preferences.
All engine data is "time stamped"
with total engine starts, Hobbs
time, day, month, year and time
of day, and are permanently stored
within the CPU module.
Instead of carrying your home
computer to your airplane to retrieve
data, a credit card size memory
device (Data card) is inserted
into a slot in the CPU module
and instantly, 100 hours of flight
data are copied. The original
data stored in the CPU is not
destroyed during this process.
Once the data report is printed
out, you have a printed log to
dispute any engine warranties
that could arise. This data card
format allows for time, day, month,
year and time tracking plane usage,
by giving each pilot a data card
and using it to retrieve data
and get an instant printout of
the flight parameters. JPI probably
has more engine data, on different
aircraft engines than the major
manufacturers have themselves.
Our experienced technicians know
what to look for when reviewing
engine data. As a service to our
customers, JPI can copy your engine
data onto floppy disk, in a spreadsheet
format for viewing on a PC compatible
computer. Also available from
JPI, a unique diagnostic software
package for diagnosing your own
engine data if that is what you
prefer. World renowned pilot and
aircraft designer, Dick Rutan
chose the EDM for his Pond Racer
Project, after having researched
many EGT manufacturing companies.
When referring to this engineering
feet of a project, Dick said "We
could not have done it without
the EDM." One of Alaska's largest
air cargo companies has logged
over 800 recorded hours on their
fleet of DC-6's.
Press the snapshot button
to instantly record all diagnostic
data when you suspect an engine
abnormality. Imagine being able
to show your maintenance department
the proof of an intermittent problem
occurring in flight. Now, that's
high tech!
Exceedence conditions are always
recorded. The EDM-700 is shipped
with conservative generic pre-programmed
factory alarm limits. The alarm
limits can be fine tuned by the
owner, but any changes in limits
are instantly recorded to show
the new limits on the next print
out. Limits can not be changed
without the owner knowing. All
probes are also checked 3 times
per second for actual alarm conditions.
False alarms are minimized by
the self diagnostic routine in
the EDM system. The probes (sensors),
are compared to real engine conditions
and are removed from the display
if they fall out of the real alarm
boundary. Should any limit be
exceeded, (EGT, CHT, CHT COOL
RATE, SPAN, RPM, Hi/lo Oil Temp/Pressure,
Hi/Lo VOLTS and TIT) a recording
of all engine parameters is taken.
The duration and maximum value
of each exceedence, along with
the exact time and date are recorded.
Alarm conditions have display
priority, and all of the EDM instruments
display the type of alarm and
its value. Twin engine aircraft
require two displays and two computers,
but JPI now has a single 3 1/8"
unit available for twin engines,
that displays both engines on
one display simultaneously.
The bottom line
on data recording is that it is
a very powerful tool. The EDM-700
makes long term trend monitoring
easy and easily verifiable on
paper. The real benefits are longer
engine life and reduced engine
maintenance costs. A complete
diary of an aircraft's flight
profile is now available for analysis
by yourself or JPI. This permanent
and unalterable record will highlight
individual performance variations
and allow for corrections before
damage occurs. How many time has
the going got rough and later,
you wondered what affect it had
on the engine? Engine warranty
claims and resales will look for
the EDM-700's total recorded hours.
