oscillation. Increasing this number generally helps to reduce oscillation associated with changing
AFR’s.
•
Number of Samplings for Avg. Error:
Defines the size of the injector pulse width modifications
when the EGO reading is changing slowly (termed the “average error”). A small number in this
parameter causes large pulse width modifications. A large number for this parameter causes small
pulse width modifications.
•
Number of Cylinder Events Between Samplings:
Defines the number of injector firings that will
occur before the EGO obtains a new sample. This allows fuel to travel through the engine with the
modified pulsewidths before the EGO reading is taken again. Larger numbers make the EGO
corrections slower.
•
Authority Range for EGO:
Defines the percentage that the EGO function is capable of adding or
subtracting from the “VE Absolute” value.
EGO Programmable Deactivation
•
High MAP Switch Above Which EGO is Disabled:
Allows the EGO to be turned off above a
specific MAP point. The system goes into open-loop mode above this MAP point, but returns to
closed loop below this point.
•
RPM Above Which MAP Switch is Active:
Defines the RPM above which the High MAP switch
is active. If the MAP reading exceeds the value in the “High MAP Switch,” but this RPM is not
exceeded, the system will remain in closed-loop mode.
•
RPM Below Which EGO is Disabled:
Turns off closed-loop operation when the engine falls
below this RPM. The TPS reading must be below the Closed Throttle Voltage for this parameter to
be engaged. This parameter is used for exhaust systems that cannot create enough heat at idle for
the EGO sensor to be accurate.
A few things to remember:
•
Standard oxygen sensors are designed to provide a
switch-point
for stoichiometric air-fuel
operation. They are NOT designed to be able to tell you the exact air-fuel ratio when you are
outside the stoichiometric amount (14.64:1 AFR).
•
Oxygen sensors have a large degree of inaccuracy when operated at different temperatures.
Figure
D.4. 7
shows a characteristic voltage curve variation with EGO sensor temperature.
•
Do not use an EGO authority range that is greater than 10% on a tuned engine. A correction greater
than a ten percent increase or decrease to the fuel curve should never be necessary on a tuned
engine.
•
It is strongly recommended that the High MAP Switch reading be set to a value BELOW 95kPa.
This will turn off the oxygen sensor correction at full-load conditions. It will save an engine from
having a lean-out condition due to the oxygen sensor reading. Never run a boosted engine in
closed-loop during high-boost situations.
•
Oxygen Sensors need heat to operate correctly. Readings obtained at idle are often inaccurate due
to this fact.
•
Although much faith is placed on air-fuel measurement, it is not the sole determining factor for
proper engine operation and fuel metering. Unless you know a specific engine’s air-fuel
requirements, there is no “target” air-fuel ratio to shoot for. However, ALWAYS run engines on
the rich side of stoichiometric when under medium to high load.
______________________________________________________________________________________
TECgt Manual Version 2.0
- Page 68 -
©2008 Electromotive, Inc.
