Electronics International SR-8A - Switch Settings for Aircraft Configuration; CHT Probe Installation

a) Swt. #1: Set this switch DOWN if you wish to scan 8 channels. Set this switch UP if you wish to
scan only 6 cylinders.
b) Swt. #2: If you have a 6-cylinder engine, the first 6 channels should be used for EGT or CHT
analysis. Therefore, set this switch DOWN. If you have a 4-cylinder engine, set this switch UP.
c) Swt. #3: Set this switch DOWN to enable the Differential Warning feature. If you plan on using
the first 4 or 6 analyzer channels of the Smart Analyzer for measuring many different kinds of tem-
peratures, you will want to disable this feature (set this switch UP).
d) Swt. #4,
EGT Analysis: If the first 4 or 6 channels are to be used for EGT analysis and you have a
fuel-injected engine, set this switch DOWN. This will set the Differential Warning limit to 95F (i.e.,
if the EGT difference between the hottest and coldest cylinder exceeds 95F, the warning light will
come on). Some fuel-injected engines have normal EGT differences as high as 150'F (some IO-520's,
IO-540's and IO-470's). Each engine has its own unique operating characteristics.
If you have a carbureted engine or a fuel-injected engine with a normal EGT difference greater than
95'F, set this switch UP. This will set the Differential Warning limit to 195F. Carbureted engines do
not distribute the fuel to the cylinders as well as most fuel-injected engines and generally have a wider
EGT spread. If you find your EGTs are always within 95F (hottest to coldest cylinder), you may
want to set this switch DOWN for better sensitivity.
e) Swt. #4,
CHT Analysis: If the first 4 or 6 channels are to be used for CHT analysis, set this switch
DOWN. This will set the Differential Warning limit to 95F. The temperature of a particular cylinder
is a function of the air flowing over that cylinder, the temperature of the adjacent cylinders and the fuel
distribution to that cylinder. Note: The automatic leaning feature only works when the first 4-6
channels are used to monitor EGT's.
3. CHT Probe Installation:
A single CHT probe should be placed on the hottest cylinder. In a 6-cylinder engine this would be one of the
center cylinders. On a 4-cylinder engine this would be one of the back cylinders.
If a second CHT probe is to be installed it should be placed on one of the front unobstructed cylinders. This
will allow you to detect shock-cooling during descents.
Most engines have a port just below the lower spark plug for the CHT probe.
If your engine has a primary
CHT probe in one of the cylinders, do not remove it. The SR-8A is not STC'd as a primary replacement
instrument. Select another cylinder for your probe. If youre putting a CHT probe on every cylinder use our
P-102 Gasket CHT Probe for your primary cylinder.
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Installation Instructions 2. Instrument Setup: