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II.
cx
2000
The object
of the system is t3 reduce
the amount
of unburnt
hydrocarbons
and the amount
of CO in the exhaust
( approximately
2 to 3
of CO ) by injectinq
air under
pressure
into the exhaust
manifold
OPERATION
:
As the enqine
rotates
air pump ( 12) supplies
the air injectors
located
near the exhaust
valves:
flap ( 13 )
prevents
the exhaust
fumes from entering
the air pump and air supply
duct assembly.
There
are two cases
where
it is necessary
to stop the injection
of air into the exhaust
manifold.
1.
During
deceleration
:
\
Durinq
fast deceleration.
the mixture
becomes
richer
combustion
is incomplete
and the injection
of air is
stopped
in order
to avoid
a second
combustion
takinq
place
in the exhaust
system
( which
would
result
in
back-firinq
) Durinq
deceleration
there
is extreme
low pressure
downstream
of the butterfly
( 1 ). This
in
turn draws
in for a short
period
of time the diaphragm
in valve ( 11 )
The air supplied
by pump ( 12 ) is released
into the atmosphere,
the calibrated
hole (( a 1) on the diaphragm
balances
the pressure
on either
side of it and the diaphraqm
returns
to its initial
position,
allowinq
air to
be once more injected
into the exhaust
manifold
2.
Wi t h
the
choke
out,
for
an
engine
coolant
temperature
of
above
45'
+ 3'
C,
and
whenever
the
coolant
tempe-
rature
remains
above
35'
i
",I
C.
In this situation
the quantities
of unburnt
hydrocarbons
and CO are very considerable
It 'is therefore
necessary
to stop the injection
of air into the exhaust
manifold
so as to avoid any excessive
increase
of temperature
in
the manifold.
On CX 2000 vehicles,
injkction
of air will
be stopped
when the enqine
water
temperature
reaches
45" + 3- C Thermal
switch
( 8 ) opens,
relay
( 9 ) 1s no lonqer
enerqized.
but electro-valve
( 7 ) remains
live
( relay
lead ). and is earthed
via the choke
control
The air pressure
at the outlet
of air-pump
( 12 ) increases
the effect of the low pressure
on the diaphraqm
in
valve
( 11 ) ( the air pressure
is felt above the diaphraq,m,
and the low pressure
produced
by the carburettor
(2)
is felt below
the diaphraqm
). the slidinq
valve
in the duct chanqes
position
and the air is expelled
into the
atmogphere
If the choke
( 10) is pushed
back in
air is once again
injected
into the exhaust
manifold
DEVICE
FOR
OPENING
THE
BUTTERFLY
:
The object
of the device
is to maintain
combustion
during
sudden
deceleration
up to an enqine
speed
of
Nd
7 1800
+ 100
rpm.
Durinq
deceleration
for any enqine
speed above
Nd,
the electronic
tachometer
housinq
( 6 ) earths
the
windinq
of relay
( 5)
Therefore
the H PIERBURG
1) electro-valve
( 4) is no lonqer
enerqized.
Electro-
valve ( 4) is then under
low-pressure,
below
the diaphragm
of the device
( 3 ) for opening
the butterfly
When the decreasinq
enqine
speed falls
below
Nd,
the electronic
tachometer
housing
(6 ) cuts out the
earth of the winding
in relay
( 5)
Therefore
the (( PIERBURG
)) electro-valve
( 4) is enerqized
The
electro-valve
is no lonqer
under
low pressure
below
the diaphraqm
of the device
(3)
for openinq
the
butterfly
the throttle
butterfly
returns
to it s stop aqainst
the idlinq
speed
adjustment
screw.
The dia-
phraqm
of the device
(3)
for openinq
the butterfly
will
once aqain
be affected
by low pressure
( under
the control
of the electronic
tachometer
housing
) once the increasing
engine
speed
reaches
NC
~ Nd
t
50
to
250
rpm
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