operating at the stoichiometric mixture. Medium and high load situations MUST be run richer than
stoichiometric to prevent engine damage, thus the EGO should be in open loop when these circumstances
are met. Many choices are available in the software to keep the EGO sensor in the correct mode (closed or
open loop) at the correct time (low or high load, etc.).
A small, but important, fact concerning the EGO operation is that when a coolant-temperature
enrichment is in place, the target Air-Fuel Ratio will be altered from the reading in the Desired Air Fuel
Ratio Table. The target Air Fuel Ratio is changed by the following equation:
Target AFR = Desired AFR Table Value – [4.34
×
(Coolant Enrichment %
÷
100)]
Therefore, when a 10% Coolant Temperature Enrichment is in the Coolant Enrichment Table, the
target AFR would be about 14.2:1 if the Desired Air Fuel Ratio Table value was 14.64:1.
A Note on One-Wire EGO Sensors
One Wire EGO sensors were used a number of years ago on early fuel-injected vehicles (and some
carbureted engines). These EGO’s output the same voltage curve as any standard 4-wire sensor, but do not
have a built-in heater or ground reference. Wire the sensor as follows:
•
Connect the wire from the EGO sensor to the EGO+ line on the
TECgt
(this is the Purple 20awg
wire in the
TECgt
Harness – Pin G33).
•
Connect the EGO- line on the
TECgt
(this is the tan 20awg wire going to Pin G32) to the Sensor
Ground line (this is black w/ white stripe 18awg wire going to Pin G6).
One-wire sensors are typically not as accurate as 4-wire sensors, since they have no built-in heater
element. Instead they must rely on exhaust system heat entirely. Unless the EGO sensor is mounted very
close to the engine in a cast iron manifold, 1-wire sensors should not be used.
G.6. Wideband O2 Sensor
Wideband Information and Installation Instructions
The
TECgt
supports an input from most wideband sensor controllers. The wideband controller must have
an analog 5-volt output signal. A typical configuration is shown in Figure G.6.1.
Figure G.6.1
- Typical Wideband Configuration
The installation of the oxygen sensor and controller should follow the wideband controller manufacturer’s
instructions. The analog 5-volt output signal connects to pin G33, O2 sensor (+) (purple wire) on the
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TECgt Manual Version 2.0
- Page 94 -
©2008 Electromotive, Inc.