Forced regeneration
In order that a regeneration can take place, following
conditions are necessary:
- exhaust gas temperature >530 ºC at particulate filter inlet
and free oxygen present (>8%);
- oxicat inlet gas temperature >230 ºC with the help from
post-injection;
- minimum time of permanence in such conditions
approximately >10 minutes.
In many cases of doubts about particulate filter cleanness
actual conditions and/or of impossibility to regenerate it
owing to very particular engine/vehicle running conditions
(persistent idling, very slow speeds and very frequent stops),
a safety forced regeneration has to be performed.
Independently of all parameters activating the regeneration,
the engine is taken to run without load to a point where
exhaust gasses have a temperature (>230 ºC) such as to
activate the reaction in the Oxicat in presence of
post-injection.
The only limit to this operation is the presence in the filter
of a particulate quantity that is in excess, being anyhow
calculated by the central unit and set as a condition to
regeneration startup.
During vehicle use, the central unit counts post-injected fuel
quantity in order to activate and maintain particulate filter
regeneration.
A small quantity of this fuel, which is injected into the
cylinders after combustion has already taken place and
remains partially unburnt, leaks out through pistons spring
rings into oil sump, accumulating to lubrication oil. Although
a part of it, evaporating, will be burnt in the engine through
recirculation system, its remaining part can degrade oil
characteristics, impairing its functionality.
Quantity of accumulated fuel may increase in case of catalyst
or engine inefficiency, and vehicle use in conditions of low
temperature and/or small amounts of miles covered.
The central unit counts the amounts of post-injections and
consequently determines the quantity of fuel accumulated in
engine oil, and warns about refilling needed.
If, after refilling engine oil, the function is not reset, the central
unit will keep on counting fuel accumulation increase even
with new oil, with consequent engine oil refilling warning.
Refilling engine oil
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