MoTeC LTCN - Manual (Page 25)

MoTeC Operation 25
Lambda Sensor
Sensor Warm-up
The internal heater in the Lambda sensor is powerful enough to allow accurate
measurement when gas temperature is at room temperature. The sensor will
take approximately 20 seconds to heat up.
The maximum continuous operating temperature of the sensor is 850 °C.
Sensors should not be used at higher temperatures for a prolonged period,
although the sensor can be heated to 930 °C for a maximum of 10 minutes.
This may however reduce the accuracy.
Sensor Lifetime
The sensor lifetime is dependent on the type of fuel being used and the volume
of gas flow over the sensor.
Sensor lifetime will be reduced by contaminants such as silicon, lead, oil, etc.
Thermal cycling and exposure to exhaust fumes without any heating control
active will also age the sensor more rapidly.
Manifold sealants can contaminate sensors. Use sealants that are sensor-
friendly to prevent reduced sensor lifetime.
When using leaded fuel, sensor element contamination will reduce the sensor
lifetime substantially. Typically sensor lifetime for high performance engines is
at least 500 hours in unleaded fuel and 50 hours in leaded fuel. Longer
lifetimes can be expected for less demanding applications. These figures are a
conservative estimate as the sensors are designed to be accurate for 50,000
km of operation in a road car.
Incorrect placement in the exhaust can overheat the sensor and significantly
reduce the sensor life. For the Bosch LSU 4.9 the sensor impedance (Ri) is an
indication of sensor temperature. In normal operation Ri should be
approximately 300 ohms. If Ri is less than 250 ohms then the sensor is being
overheated. Ri is included in the transmitted CAN messages. Due to the
different control system for the NTK sensor the Ri parameter is not applicable.
At the end of its life the sensor becomes slow to respond and does not read
rich properly. Regular performance of the Free Air Calibration (see
Calibration )
will maintain the accuracy of the sensor over its lifetime.