Supplement to Manual 818-1 ADD
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OPERATION
N-
MA.IE.
144-00
(haracteristics
0/
the
« L.Jetronic
» electro;,ic Op.
MA.IE.
144-00
9
Joel izjectian system.
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-conduct.ing
components condeisers, calibrating
resistors and
filters so
as
to
avoid.any
interference.
The function
of
the
E.C.U. is
to supply an impulse
to the
injectors, and to
control their opening
for ci precisely
defined amount
of time. The EC.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
cycie
),
injecting
haif the quantity
of
fuel reciuired each
time.
With
this
systern.
it is not
necessary
for
the camshaft angle to
coincide with
the beginning
of injection point,
which
eliminates the
need for
ci
generciting
switch ircorporated in
the
distributor.
4
0
c
0
0
z
c
5
E
0.
0.
The
injection iihpulse control is ensured by
the distributor impulses.
The
distributor produces four imp
ses
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
distribnto are transformoted
into
square
waves
by the
wave
form
shc.per. Since
injection only occurs
twic?
for
ecich
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
caiculating the
duration
of injection.
At
the
multiplying
stege
of
the
E.CU.
various
correction
vcxlues (full bad
and
idling speed
via
throttle butterfly
spindle
switch,
engine temperature via
the
water
temperature sensor. air temperature via the
air-temperature
sensor
loccited
in the air-flow
sensor
)
are
combined
with
the signals from the air-flow sensor
and
the
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 increoses,
the injection
duration
increcxses.
The f act
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
voltag
in
the
E.C.U.
The
final
impulse detemines
the
time
during
which
the
injectors
are
connected to
earth
(
injection
durution
supplied
by the output
stege
).
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