Lambda Probe; Catalytic Muffler; Fuel Vapour Emission Control System - Alfa Romeo 33 Workshop Manual

The iollowing components are fore
converter.
O
with ~a special device which prevents
the ne& of the filler inlet, thus ope-
ning ~the valve and filling the tank.
The sensitive element of the lambda
probe consists of a ceramic capsule
coated wlth porous platinum on both
the /nternal side cornes into contact
with'atmospheric air.
between the air of the atmosphere and
the r$xhaust gases is transformed into
a n 8ele,ctrical potential difference
the stechiometric air-petrol ratio re-
quired for the maximum operating effi-
harrhful 'emissions contained in the
exhaust gases to a minimum.
The probe is electrically preheated to

1 Lambda Probe

CATALYTIC MUFFLER

A catalytic converter is mounted in the
exhaust system with the purpose of
reducing exhaust emissions. The con-
R
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-
formation of the metallic container
and deterioration of the alumina'and a
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-'
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-
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
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
mospheric air thus maintaining the sy-
,
spring which is set in such a way as to
pressure in the tank be excessive. In
scharged into the vapour filter @
O c t o b e r 1 9 8 8