Emission Control Systems: Description and Operation

Exhaust emission control
The multiport Sequential Fuel injection (SFI) system provides accurately metered quantities of fuel to the combustion chambers to ensure the most efficient air to fuel ratio under all conditions of operation. A further improvement to combustion is made by measuring the oxygen content of the exhaust gases to enable the quantity of fuel injected to be varied, according to conditions, to correct any unsatisfactory composition of the exhaust.
The main components of the exhaust emission system are two catalytic converters which are an integral part of the front exhaust pipe assembly. The catalytic converters are included in the system to reduce the emission, to atmosphere, of carbon monoxide, oxides of nitrogen, and hydrocarbons. The active constituents of the converters are platinum and rhodium. The correct functioning of the converters is dependent upon close control of the oxygen concentration in the exhaust gas entering the catalyst. The oxygen content of the exhaust gas is signalled to the Engine Control Module (ECM) by Heated Oxygen Sensors (HO2S) located in the exhaust front pipes each side of the catalytic converters. The ECM can then make an appropriate adjustment to the fuel supply to correct the composition of the exhaust gases.


CAUTION : Unleaded fuel only must be used on vehicles fitted with catalytic converters. As a reminder a label to indicate this is adhered to the inside of the fuel filler flap. As a further safeguard, the filler neck is designed to accommodate only unleaded fuel pump nozzles.