Technical data
The iollowing components are
fore
seen
~
on~ly
on
models
with catalytic
converter.
FiLtiEl+INLET FOR
U,F$EADED
PETROL
Thé
filIer
inlet of the fuel tank is fitted
with
~a
special
device
which prevents
‘filling with petrols other than those
whlich
are unleaded.
O’nly
lthe~
delivery nozzles of unleaded
petrol
pumps
are able to pass through
the
ne&
of the filler inlet, thus
ope-
ning
~the
valve and filling the tank.
LA~B~A
P;ROBE
The sensitive element of the lambda
probe consists of a ceramic capsule
coated
wlth
porous platinum on both
sides;
the
external
side
cornes into
contact,with the exhaust gases, whilst
the
/nternal
side
cornes into contact
with’atmospheric air.
The
~difference
in the oxygen content
between the air of the atmosphere and
the
r$xhaust
gases is transformed into
an
8ele,ctrical
potential difference
aqross
~the
two
sides
of the capsule.
Thisi
electrical signal is ‘sent
to’
the,
electronic CUwhich
carries
out
those
correct)o’ns
necessar = y for obtaining
the stechiometric air-petrol ratio
re-
quired for the maximum operating
effi-
cenqy
of the catalyst, thus keeping
harrhful
‘emissions
contained
in the
exhaust gases to a minimum.
The probe is electrically preheated to
obtain
a,faster response time.
1 Lambda Probe
PA~2~9E0883301
CATALYTIC MUFFLER
A catalytic converter is mounted in the
exhaust system with the
purpose
of
reducing exhaust emissions. The
con-
verter consists of an alumina,monol/th
coated with
anactive
material
compo-
sed of noble metals and housed in a
special steel container which is
resi-
stant to high temperatures. The
sy-
stem converts’the HC and CO
semis-
sions
contained
in the exhaust gases
into waterand CO, (non-toxic substan-
ces).
The catalyst
is
efficient within a cer-
tain temperature range. At low
tempe-
ratures no catalytic conversion
oc-
curs.
High temperatures
cari
cause
de-
formation of the metallic container
and deterioration of the alumina’and a
consequent
loss in the efficency
,of
the operation ~ of the catalyst
~itself.
High temperatures
cari
be
caused
by
an excessive quantity of unburnt fuel
passing through the alumina, follo-
wing overloading of the engine or by
the engine being badly tuned
and
out
of adjustment.
*
1 Catalytic muffler
,
:’
FUEL
~APOUR~EMISSION
CONTROL SYSTEM
Fuel va ours emanating from the
fuels
tank
d
4
are collected, by
means
of
a’
special tube
0
in a liquid vapour
se-’
1’
parator
@
which-is
arranged in
such
a way as to permit the return of
con-
densed fuel to the tank.
The tank has a sealed filler cap to
pre-
vent fuel vapours from escaping into
the atmosphere.
The fuel vapours
coming
from the
se-
parator
0
through the
Upper
outlet,
are conveyed to a fuel vapour
filter
6B.
The
vapour
flow is controlled by a val-
ve
q
which opens or closes the
pas-
sage’to
the fuel
filter
in relation to the
vacuum pressure existïng upstream
the throttle body. When the vacuum
pressure is lower than the specified
value
(e.g.
with the engine switched
off or on idle) the dump valve is closed
and prevents vapours from flowing to
the
vapour
filter.
If this is not the case
(engine running
under
normal condi-
tions) the valve is
open
and the fuel
va-
pours are able to flow to the
filter
whe-
re they are absorbed by activated
car-
bon.
As a result of the
difference
in pressu-
re existing inside the
vapour
filter,
the
activated
carbon
is “washed” by a
current
of air.
The vacuum pressure is taken
up-
stream
;the
throttle. In the “washing”
action, the fuel vapours mlxed with
at-
mospheric air are conveyedto the
sup-
ply
manifold
where they are added to
the air taken in by the engine.
Should the pressure in the fuel vapour
separator tend to a drop when the
en-
gine is stopped, due to a
fall
in tempe-
rature, a compensation valve
@
si-
tuated in the fuel
vapour
recovery
tu-
bing
@
between the separator
0
and~the
vapour
filter
@
, lets in
at-
mospheric air thus maintaining the
sy-
stem
at atmospheric pressure.
Thel
dump valve
@
as an
interna1
spring which is set in
such
a way as to
open
the passage should the
vapour
pressure in the tank be excessive. In
this,
case the fuel vapours
cari
be
di-
scharged into the
vapour
filter
@
and:
held in the activated carbon’of the
fiiter
itself.
October 1988