Santana PS-10, Руководство по обслуживанию, Страница: 405 / 627

ENGINE FUEL AND EMISSION CONTROL SYSTEM 6C-23
Control and anticipation of main and pilot injection
According to the signals coming from the different sensors,
including the absolute pressure built-in sensor, the control
unit determines, using an internal program, the point of
optimum injection
Injection pressure closed cycle control
According to the engine load and determined by the signals
coming from the sensors, the control board controls the
regulator to obtain an optimal line pressure.
Fuel dose
The fuel dose is calculated according to:
-the accelerator stroke position.
-the engine speed.
The result can be corrected according to:
-the water temperature.
Or to avoid:
- noise.
- fumes.
- overload.
- overheating.
- turbocompressor turbine alteration.
The delivery can be modified in the event of:
- intervention of external devices ABS, ABD, EDB (if fitted)
- serious obstacles which cause the reduction of the load
or engine stoppage.
The control unit calculates the fuel to be injected in the
appropriate cylinder (mg per delivery) after taking noting
admission air temperature and fuel temperature.
The fuel mass calculated is first converted into volume
(mm
3
per delivery) and then into injection duration.
Flow correction according to refrigerant temperature
When engine is cold, it faces greater resistance in its
working; mechanical friction is high, the oil is still viscous,
free movement has not been optimized.
Furthermore the injected fuel tends to condense on the
still cold metal surfaces.
The fuel dose is greater when the engine is cold than when
it is hot.
Flow correction to avoid noise, fumes and overloading
Given that the causes of such inconveniences are known,
the control unit has been programmed to avoid them.
De-rating
In the event of engine overheating, the injection is modified,
reducing the flow proportionately to the temperature reached
by the refrigerant fluid.
Rev egulation from variable geometry turbocharger
turbine (if fitted)
The turbine speed is continually regulated and can be
corrected by acting on the variable geometry.
The advance injection electronic control
The advance (instant of delivery start, expressed in degrees)
can be different from one injection to another, and from one
cylinder to another, and is calculated, similar to the flow,
according to the engine load (accelerator position, engine
speed and introduced air).
The advance is suitably corrected:
-on aceleration phases.
According to the coolant temperature in order to:
-reduce exhaust, noise and overloading
-improved vehicle acceleration
Starting the engine requires a high advance according to
the refrigerant temperature.
Feed-back from the instant of delivery start is given by the
resistance valve of the injector electro-valve.
Speed regulator
The electronic speed regulator presents the following
characteristics:
-minimum and maximum
-all regimes
It remains stable in ranges where the traditional mechanical
regulators can be imprecise.
Engine starting
In the first starting turns of the engine, the synchronisation of
the stage signals and the recognition of cylinder nº1
(crankshaft sensor and camshaft sensor). When starting,
the signal from the accelerator pedal is ignored. The start
flow is established according to the engine coolant
temperature only, by means of a map.
When the control unit records a number of revs and an
acceleration of the flywheel, it can consider that the engine
is now running and not being turned by the starting motor
and thus re-connect the accelerator stroke sensor.