Ducati Diavel Workshop Manual page 283

Introduction to the engine control system
- Combustion with rich mixture -> low oxygen levels in exhaust gases -> oxygen sensor voltage is high (approaching 1 V)
This electrical signal is transmitted to the ECU via the sensor output connection. The oxygen sensor only starts functioning
correctly at temperatures of at least 300°C. At these temperatures, the zirconium dioxide element becomes permeable to
oxygen ions, meaning that it can be crossed by the ions themselves, generating a difference in potential between the two
platinum surfaces. To reach operating temperature more rapidly, there is an electric heating element inside the sensor
itself, which receives 12V power and has a ground connection controlled by the ECU in PWM (Pulse Width Modulation)
mode. The PWM percentage is modified by the ECU in relation to engine temperature, to heat the oxygen sensor to
operating temperature rapidly after a cold start. Heater element control is disabled in KEY ON state with the engine off
and during starting (ECU does not provide connection to ground in these conditions).
To allow the oxygen sensor to reach operating temperature rapidly, a heating element is included within its housing,
which receives 12 V power and has a ground connection controlled as required by the ECU. The signal generated by the
sensor switches from a voltage close to 1V to a voltage approaching 0V when the fuel-air mixture reaches a near-
stoichiometric ratio (air-fuel ratio of 14.7).
Operating principle of the catalytic converter
The catalytic converter consists of a monolith metallic core with a honeycomb structure. It therefore has hundreds of small
channels, which are covered with a layer of aluminium oxide washcoat. The exhaust gases are passed through this
honeycomb structure. The catalyst substances (noble metals), such as platinum, rhodium and palladium, with which the
products of combustion come into contact, are deposited on the washcoat layer. The principle reactions taking place in a
three-way catalytic converter oxidising CO and HC and reducing NOx are as follows:
- CO reacts with oxygen to produce water (H 2 O) and carbon dioxide (CO 2 )
- HC compounds react with oxygen to produce water (H 2 O) and carbon dioxide (CO 2 )
- NOx compounds react with CO to produce nitrogen (N 2 ) and carbon dioxide (CO 2 )
These reactions only begin to develop once the catalytic converter reaches a temperature of at least approximately 300°C.
This exhaust post-treatment device does not have an unlimited lifespan, and its effectiveness is reduced with increasing
mileage. The lifespan of the catalytic converter is significantly reduced if it comes into contact with high quantities of
unburnt fuel. As a result, never attempt to push-start the motorcycle if starting is impeded by a mechanical or electrical
fault. Furthermore, the ignition system must always be in perfect working order. Only use engine oil specified by Ducati,
as it has a low ash content (ash obstructs the tiny catalytic converter channels over time).
The image shows a monolith core in excellent condition.