G4 Wiring and Installation Manual26
© 2009 Link
enter this information into the ECU via PCLink Tuning Software. Note that most commonly
used sensors calibrations are available by selecting them in PCLink Tuning Software.
7.6 Narrow Band Oxygen Sensor
A narrow-band exhaust gas oxygen (EGO) sensor is very accurate at air/fuel ratios near
14.7:1 (for petrol). At richer or leaner are/fuel ratios there is a very small output signal
change for large changes in air/fuel ratio. This makes the narrow-band sensor very good at
detecting either a lean or rich condition, but not very useful for detecting how lean or rich.
For this reason, a narrow-band sensor is not recommended for tuning purposes. However a
narrow band sensor is suitable for running Closed Loop Lambda (CLL). CLL allows the ECU
to self tune at cruise to improve economy and emissions.
There are many variations of EGO sensors although most are identical in terms of the
output signal. The principal differences are mostly physical involving lead tolerance, heated
or unheated, mounting methods, and whether or not a signal ground wire is supplied.
Lead Tolerance
The lead additives used in most high-octane fuel (aviation gas or race gas) will reduced the
lifespan of the sensor considerably. Some probes are shielded and are more tolerant than
others.
Heating
Many probes incorporate an electrical heating element, which is powered by the vehicles 12
Volt supply. These heaters allow the probe to be mounted in cooler portions of the exhaust
system and significantly improve the probe performance at idle and during warm up phases
of operation. This is because the probe temperature must exceed 300ºC before accurate
readings are possible.
An Auxiliary Output can be used to control the heating of the oxygen sensor if required. To
do this, ground the sensors heater wire through any of the ECU's auxiliary channels.
Mounting
Most probes have an M18 x 1.5 metric thread designed to screw into a mating boss. Some
variants use a bolted flange arrangement, but these are relatively uncommon.
Almost all EFI engines will have a probe installed as original equipment in the exhaust
manifold or turbo housing.
If the vehicle does not have a factory fitted EGO sensor, it will be necessary to manufacture
a sensor mount according to engine type and layout.
The ideal mounting position of the sensor in the exhaust can vary depending on the
application. Most of the time the preferred position is in the exhaust manifold collector on a
naturally aspirated engine or after the turbocharger on a turbocharged engine. However, a
location further down the exhaust is acceptable provided the probe is adequately heated.
Note that it is also possible to get an EGO sensor too hot which also causes an inaccurate
reading. Therefore in applications with particularly high exhaust gas temperatures (e.g.
turbo engines, rotary engines) it may be necessary to either use an unheated sensor or
move a heated sensor further down the exhaust.
Caution: EGO sensors use ceramic material internally and are susceptible to impact
damage. Handle probes carefully to avoid impacts at all times.
Narrow Band Oxygen Sensor Wiring
Typically narrow-band EGO sensors can be recognised as having one, two, three or four
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