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Engine control systems
The B5254F-engine is controlled by
t wo advanced electronic control sys-
tems, the LH 3.2 fuel injection system
and the EZ 129K ignitlon system.
These systems are further develop-
ments of the well known systems used
in the current four-cylinder Volvo
cars.
The development goal has been to
produce a completely integrated sys-
tem, based on the current components,
which is less expensive, more flexible,
more reliable and more efficient. A
new cable harness concept is used,
and the engine control units include
the functions of a number of elec-
tronic relays to reduce the number of
components (figure 19).
Fuel injection system
L H3.2
The system has a new air mass meter
of hot-film type. Together with an an-
gular position throttle potentiometer,
it gives an accurate air mass measure
at low cost. It has a closed-loop lamb-
da control and an idle speed control,
both with adaptive functions.
Previously each system in the ve-
hicle has had its own temperature sen-
sor for coolant temperature. On this
engine, however, there is only one
sensor of so-called NTC-type. This
signal is used by the LH3.2 to form a
period-time modulated signal to all
other systems which need this in-
formation.
While the electronic control unit
has been moved from the passenger
compartm ent to the engine compart-
ment, the fuel pump relay has for safe-
ty reasons been replaced by an elec-
tronic type. It is kept triggered by the
control unit with a constant pulse
train, instead of just a "high" or "low"
signal. This is also for safety reasons
to avoid the possibility of petrol leak-
age in the engine compartment caused
by a broken fuel pipe and a running
fuel pump after a crash.
Ignition system EZ129K
To measure the engine speed and an-
gular position, a flywheel speed sen-
sor of inductive type and a camshaft
position sensor of Hall-effect type are
used. The system has two knock-
sensors for best performance of the ig-
nition timing regulation of each cyl-
inder, with adaptive functions. The
electronic control unit also controls
the V-VIS system plus the air condi-
tioning compressor and the electric
cooling fans.
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