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OPEdATlON
N- MA.IE. 144-00 : C1
3aractcJristics
o/ the e L-Jetro~ic
n elcctrorlir
Op. MA.IE. 144-00
9
fuel injectian
systwn.
E.C.U; ( ELECTRONIC CONTROL UNIT )
Apart
from three
integrated
circuits
( I.C. ) forming
the main part of the E.C.U.,
there are in addition
only a few
semi-conducting
components
condensers,
calibrating
resistors
and filters
so as to avoid.any
interference.
I
The function
of the E.C.U.
is ,to supply
an impulse
to the injectors,
and to control
their
opening
for a precisely
defined
amount
of time.
The E.C.U.
to this effect uses the information
provided
by all the engine
sensors
which
translate
the operating
conditions
of the engine
into electric
impulses.
All the injectors
are connected
in parallel,
and inject
fuel simultaneously
twice
for each rotation
of the camshaft
( therefore,twice
for each engine
cycle
), injecting
half the quantity
of fuel required
each time
With this system
it is not necessary
for the camshaft
angle
to coincide
with
the beginning
of injection
point,
which
eliminates
the
need for a generating
switch
incorporated
in the distributor.
The injection
impulse
control
is ensured
by the distributor
impulses.
The distributor
produces
four impulses
for
every operational
cycle.
Since
injection
only occurs
twice
in every cycle,
the E.C.U.
must divide
the frequency
by 2.
The impulses
coming
from the distriLti,
are transformated
into square
waves
by the waveform
shaper.
Since
injection
only occurs
twice
for each camshaft
rotation,
whereas
the distributor
provides
4 impulses
in the same
amount
of time,
the frequency
of the impulses
must be divided
by 2 in the frequency
divider.
These
signals
are used to charge
a condenser.
The condenser
discharge
determines
the beginning
of injection
point;
the position
of the air-flow
sensor
flap ( which
determines
the quantity
of air drawn
in ) being
the main
parameter
for calculating
the duration
of injection.
At the multiplying
stage of the E.C.U.,
various
correction
values
( full load and idling
speed
via throttle
butterfly
spindle
switch,
engine
temperature
via the water
temperature
sensor,
air temperature
via the air-temperature
sensor
located
in the air-flow
sensor
) are combined
with
the signals
from the air-flow
sensor
and the injt,ztion
frequency
in order
to determine
the injection
duration
which
is transmitted
to the injectors
by way of impulses.
The time it takes
for the injector
needle
to open and close
depends
on the battery
voltage.
As the supply
voltage
increases,
the injection
duration
increases.
The fact that the quantity
of fuel injected
depends
on the voltage
is cancelled
out by the fact that the injection
duration
is inversely
proportional
to the voltaqq,in
the
E.C.U.
The final
impulse
determines
the time during
which
the injectors
are connected
to earth
( injection
duration
'supplied
by the output
stage
).
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