Exhaust emission control

Exhaust emission control

The engine management 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 maintaining the ratio necessary for efficient gas conversion by the catalytic converter.

The catalytic converter is situated between the exhaust front pipe and exhaust intermediate pipe. The catalytic converter reduces the emission of Carbon monoxide, Oxides of Nitrogen (NO_x) and Hydrocarbons released into the atmosphere. The active constituents of the converter are the precious metals Platinum and Rhodium.

’K’ series models

The correct operation of the catalytic converter is dependent upon close control of the oxygen concentration in the exhaust gas entering the converter. The quantity of oxygen in the exhaust gas is determined by a heated oxygen sensor situated in the exhaust front pipe. The heated oxygen sensor provides the engine control module with a signal proportional to the oxygen content. The ECM can then determine whether any adjustment is required to the amount of fuel being injected to achieve the correct exhaust gas content, and implement the required changes.

CAUTION: Serious damage to the catalytic converter will occur if leaded fuel is used. The filler neck is designed to accommodate only unleaded fuel pump nozzles.

Exhaust gas recirculation (EGR) - ’L’ series models

During certain running conditions the EGR system directs exhaust gases into the intake manifold to be used in the combustion process. The principal effect of this is to reduce combustion temperatures, which in turn reduces Oxides of Nitrogen (NO_x) emissions.

The EGR diaphragm valve is vacuum operated through a solenoid valve, mounted on the right hand suspension turret. When the Engine Control Module (ECM) determines that exhaust gas recirculation should take place, the solenoid valve is modulated and vacuum, supplied by the brake servo vacuum pump, opens the EGR valve. Exhaust gases are then fed through a pipe into the inlet manifold.

An air flow meter, mounted in the air intake pipe, senses the volume of air entering the engine. Using the principle that an increase in EGR will lead to a decrease in the intake air flow, the air flow meter is used by the ECM to monitor the amount of exhaust gases being recirculated. This feedback signal allows the ECM to accurately control the volume of exhaust gases being recirculated.