Lambda Sensor - Ducati Monster 696 2009 Manual

section
M 3

Lambda sensor

The Lambda sensor, positioned on the exhaust pipe, transmits information to the ECU on the amount of oxygen present in the
exhaust fumes. With this information the ECU can maintain optimal control over the fuel-air mixture.
The outer surface of the sensor element in zirconium dioxide is in direct contact with the exhaust gas, while the inner surface is
in contact with the atmosphere. Both surfaces are coated with a thin layer of platinum. Oxygen in ionic form travels through the
ceramic layer and charges the platinum layer electrostatically so that the platinum acts as an electrode: the electrical signal
generated is carried on the sensor output cable.
the zirconium dioxide element becomes permeable to oxygen ions at a temperature of around 300 °C.
When the oxygen concentration is different on the two sensor surfaces, a voltage is generated thanks to the special physical
properties of the zirconium dioxide. With a lean mixture the signal voltage is low, while with a rich mixture it is high.
The typical change in signal intensity occurs when the air-fuel ratio is 14.7 to 1 (14.7 parts of air to 1 part of petrol), which
is referred to as "Lambda 1". This ratio is considered to be an indication of complete combustion, hence the name
"Lambda Sensor" (oxygen sensor) therefore
lambda = 1 means mixture in stoichiometric (ideal) ratio
lambda >1 means a lean mixture
lambda <1 means a rich mixture.
The air-fuel mixture control system is managed by the lambda sensor, which starts to operate at over 300 °C: the ceramic material
starts conducting oxygen ions at around 300 °C. If the proportion of oxygen starts to differ between the two ends of the probe,
this generates an electrical voltage between the two electrodes due to the particular nature of the material. This makes it possible
to measure the difference in oxygen content between the exhaust gas and the ambient air. Combusted gas still contains a
residual amount of oxygen when the air-fuel mixture delivered to the combustion chamber is incorrect. This makes it possible
to adjust the injection control unit to ensure the engine always runs with the optimal air-fuel mixture.
Monster 696/696+ - M.Y. 2009 - edition 00
Fuel injection-ignition system
1
1
A
B
C
D
E
F
G
H
L
M
N
P
15