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10
OPERATION
N°
MA.IE.
144-00
Characterjstics
oj
the
« L.Jetronic »electronic
juel
injection
systern.
AIR-FLOW
SENSOR (1):
The role
of
the
air-flow sensor is to
supply
the
E.C.U. with a signal
proportional
in voltage to
the quantity of air
drawn in.
-
With
the engine running,
the
sensor flap
is maintained
at an angular
position
determined
by
the intensity
of the-air-
flow, against the
resistive action of a spiral spring. The resistance
to
del
lection
of the
sensor
flap,
produced
by the
spira!
spring, is
calculated
so as
to
compensate for any mechanical friction (bearings,
bushes
)
and
to
limit the
pressure
drop
at
the
flap.
The
movement of the sensor flap is damped
by
a blade rigidly attached to it. This damping
blade
rotates inside a
housing in which
it
is a
close fit.
The operating clearance determines the degree of
damping.
The use
of
a damping
blade
cancels
the effects
on
the
angular
position of
the sensor
fiap of
pressure
variations in
the
inlet
collector.
A
potentiometer, actuated
by
the sensor flap
spindle,
transforms
movement
of
the
sensor 1 lap
into
an electrical
circuit
which is trarisinitted to the
E.C.U..
The
voltage of the electrical current
-is inversely
proportional to the
amount
of air
drawn
in.
In
order
to
cancel the
effects of any
combustion
taking
place
in
the
inlet
manifold,
a
one-way valve is
incorporated
in
the sensor
flap.
Thanks
to a by-pass
channel, a
small
quantity
of the
air
drawn -in by-passes
the sensor
flap. This
offers
the
possibility
of
determining
the air/fuel rnixture
at idling
speed
by'varying the
diameter of
the
by-pass channel,
since the
air going
through
the by-pass
is not measured. The
switch for
the
pump
(
engine
running
)
and the air temperature sensor
are
located in
the
air-flow sensor
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