J.P. Instruments EDM 760 Pilots Guide - Manual (Page 6)

With the EDM-760 it is now possible to have substantially more
diagnostic information available to you in a timely and usable manner.
The included data memory permits you to record all measurements for
later down loading to your laptop or Palm handheld.
Benefits of Proper Mixture Control
• Improved engine efficiency • Reduced maintenance
costs
• Greater fuel economy • Reduced operating costs
• Smoother engine operation • Proper engine
temperatures
• Longer spark plug life • Reduced engine vibration
JPI Probes
Temperature information processed
by the EDM-760 is captured by fast
response, grounded
JPI
temperature probes, that accurately
measure the small temperature
changes—as small as 1°F—that
occur during mixture adjustment.
Temperature and Mixture
In a piston engine only a small portion of the energy from combustion
produces movement of the piston during the power stroke. The majority of
energy passes into the exhaust pipe as hot gasses. By monitoring the
temperature of these exhaust gasses you will have an indication of the
quality of the combustion process. Low compression, non-uniform fuel
distribution, faulty ignition, and clogged injectors diminish the efficiency
of the combustion process that generates power.
From the cockpit you can adjust the fuel/air ratio by a process called
leaning. Retarding the mixture control changes the fuel/air ratio and hence
the resulting Exhaust Gas Temperature (EGT).
The following figure depicts the mixture and temperature relationship.
Page 2 Engine Data Management
CHT probe
EGT probe
cylinder
head
exhaust
manifold