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XDI200 Manual Version 0.1
- Page 51 -
©2017 Electromotive, Inc.
Electromotive’s EGO sensors also follow this color code, and are mated to a 4-position female
weather-pack connector in the following pin out:
Gray: Pin D Black : Pin C White : Pin B White : Pin A
The heater circuitry allows the EGO sensor to warm up quickly. It also keeps the EGO as
warm as possible during idling conditions, where unheated EGO sensors (1-wire style) often cool
down significantly. The positive wire for the heater can be spliced to the Fuel Pump output on the
XDI200
Power Harness (PN 070-40000). This is the 16awg light green wire. This is NOT the
same as the Fuel Pump Relay Ground output of the
XDI200
, which is a 20awg light green wire
from pin [57].
If the Power Harness for the
XDI200
is not being used for the EGO heater element, the
EGO heater should be wired to a switched voltage source. If it is wired to a full-time voltage
source, it will drain the battery in short order! See
Figure 56
for proper wiring.
Figure 56.
Wiring details for Electromotive’s EGO sensor (PN 315-72120).
5.6.3 EGO Functionality
When using an EGO sensor
, it must be realized that AFR’s that are not near the
stoichiometric value are not accurate. The stoichiometric value is the AFR that results in
complete combustion with no excess fuel (gas, alcohol, etc.) or excess air (oxygen). In simple
terms, the stoichiometric value is AFR at which the incoming mixture is neither
lean
nor
rich
.
Read the section on Oxygen Sensor Corrections for more information.
The reason for inaccuracies when away from the stoichiometric AFR is simple: EGO
sensors are only designed to provide a
switch-point
at the stoichiometric AFR. The voltage
goes from a low reading (approaching 0 volts) when lean to a high reading (approaching 1 volt)
when rich. Note that the
XDI200
software multiplies the EGO input voltage by a factor of 5 when
displayed on the engine monitor and datalog screens. Thus, the maximum value that could be
obtained for a rich mixture would be 5volts, not 1volt. Instead of being a straight line between
lean and rich, the curve is like the one depicted in
Figure 98
. Additionally, the EGO curve
changes with exhaust gas temperature, thus nullifying calibration data made at a particular
exhaust temperature when used at a different temperature.
Along with these negatives comes a positive: an EGO sensor is typically good at providing
a stoichiometric measurement when at idle or part-throttle cruising.
