Mazda 6 Facelift 2005, Training Manual

Page: 89 / 274

Engine Diesel Engines
Regeneration Process
•
Due to the effect of the catalytic coating the diesel particles are burnt off above a
temperature of 500 °C. Since the exhaust gas temperature during normal driving is
between 150…400 °C (depending on the engine operating conditions), it must be
increased artificially by external intervention from the engine management system to
start the regeneration process.
•
If regeneration of the DPF is required, the PCM checks whether the engine operating
conditions are suitable to start the regeneration process. If the requirements for
regeneration are met, the PCM performs the following measures to artificially increase
the exhaust gas temperature:
–
Closing the EGR valve to increase the combustion temperature by increasing the
oxygen proportion of the cylinder charge
–
Closing the ISV partially to increase the intake air temperature by throttling
–
Performing an early post-injection to increase the combustion temperature by
burning an additional fuel amount
–
Performing two late post-injections to increase the exhaust gas temperature by
burning fuel in the oxidation catalytic converter
•
By these measures the minimum exhaust gas temperature of 150 °C (at low engine load
and engine speed) is increased to 500 °C and regeneration starts. Then the PCM
monitors the regeneration process using the signals from the DPF differential pressure
sensor and from the exhaust gas temperature sensors. Control over the regeneration
process is critically important since the DPF is damaged when its temperature exceeds
1000 °C.
•
The regeneration process takes up to 15 min. When regeneration has started it will be
completed regardless of the engine operating conditions. It is only stopped when the
engine is shut off. In this case, the regeneration process is started again once the
required operating conditions are met.
Service Training Mazda6 Facelift 01-75