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Supplement to Manual 818.1 ADD
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OPERATION
N°
MA.IE.
144-00
Characteris/ics of
tbc'
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I,.Jctron/c
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Op. MA.IE.
144-00
17
fuc'l i?ijeCtiOfl
s''SIeni.
SUPPLEMENTARY AIR CONTROL
(
1):
At idling speed and
when
cold, the
engine must
produce riore
torque so as to counteract
increased resistance
caused
by
friction.
In
addition
to
an
enriched air fuel
mixture, the engine also
needs, when
starting
from cold
and during
the warming-up period,
to be supplied
with
supplementary
air.
The E.C.U.
compensates
for this
supplementary
air
by
providing more
fuel;
the
engine therefore
has
a
larger amount
of mixture
at
its disposal
to
reach
normal running temperature.
The supplementary air
control fitted
in
parallel
with the
throttle butterfly
supplies
the
supplementary
air. The supplementary air
control is heated
only
when
the engine
is
running and
its heater
winding
is supplied electrically as
long
as
the ignition
is switched on.
The location
of
the
supplementary air control
'on the
engine
block
was
selected
for
its good heat transfer charac-
teristics,
and
so
as
to
subject
the unit to the changing
ambient temperature
of the engine.
The
opening section
of the supplementary
air
control
is
automatically adjusted
accordirig
to
the
temperature,
so
that the required
idling speed
is
maintained
regardiess of engine temperature.
When
the latter
increases,
the
air
channel
is gradually
reduced, until
it is completely
closed when the
coolant temperature
reaches approximately
+60°C.
,
0
c
0
0
z
c
4;
0
0.
1)
The
supplementary
air
control is
situated
at
a representative
spot fo.r
engine
running temperature.
A bi-metal
spring
actuates
a
rotary
valve thereby altering
the
size of
the
air
passage.
Electric heating
has th advontage
of allowing
the. supplementary
air
to
be
adjusted at pre-set
times.
SWITCH ON
THROTTLE
BUTTERFLY
SPINDLE:
The
switch on the
throttle butterfly
spindle contains
two contacts
the
idling speed
contact, and the full bad
contact.
The
control
contact,
whichslides along
a
slot, closes the
idling
speed
contact or
the full
bad
contact for a
givri
position of
the butterfly.
The
E.C.U. analyses
the signals received
so as to adjust the
duration
of
injection.
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