Operation - CITROEN CX 2000 Repair Manual

ALL CX VEHICLES
ANTI-POLLUTION SYSTEM ( SWEDISH MARKET )
I - cx 2200 :
The object of the system is to reduce the amount of unburnt hydrocarbons and the amount of CO in the exhaust
( 2 to 3 Z. of CO ) by injecting air under pressure into the exhaust manifold
OPERATION :
As the engine rotates air pump ( 1 )supplies the air injectors (4) situated close to the exhaust valves: flap (3)
prevents the exhaust fumes from entering the air pump ( 1 ) and valve ( 2) assembly
There are two cases when it is necessary to stop the injection of air into the exhaust manifold.
1. During deceleration :
During fast decelerations.
the mixture becomes richer combustion is incomplete, and the injection of air is
stopped in order 1.0 avoid a second combustion taking place in the exhaust system ( which would result in back
firinq ). During deceleration there is extreme low pressure downstream of the but!erfly ( 8 ). This in turn draws
in for a short period of time the diaphragm in valve (2 )
The air supplied by pump ( 1 ) is released into the atmosphere the calibrated hole u a )) on the diaphraqm
balances the pressure on either side of it, and the diaphragm returns to its initial position, allowinq air to
be once more injected into the exhaust manifold.
2. With the choke out :
With the choke in this position,
the quantities of unburned hydrocarbons and CO are very considerable. It is
therefore necessary to stop the injection of air into the exhaust manifold so as to avoid an excessive
increase of temperature in the manifold. With the choke out, lever ( 5 ) connects relay ( 7 ) to earth.
The u WEBER )) electric contact is enerqized The air pressure at the outlet of air pump ( 1 ) increases the
effect of the low pressure on the diaphragm in valve (2 ) ( the air-pressure is felt above the diaphragm and
the low pressure produced by the carburettor (8) is felt below the diaphraqm ) the sliding valve in valve
unit ( 2 ) changes position, and the air is expelled into the atmosphere
If choke ( 5) is pushed back in, air is once again injected into the exhaust manifold.