Emission control systems

EMISSION CONTROL SYSTEMS

The vehicle is fitted with various items of emission and evaporative control components to comply with emission regulation requirements.

Three control systems are used to reduce harmful emissions released into the atmosphere from the vehicle at all times, and under all conditions. These are:

1. Crankcase emission control
2. Exhaust emission control
3. Fuel vapour evaporative loss control

In many countries it is against the law for a vehicle owner or an unauthorised repair shop to modify or tamper with emission control equipment. In this event the vehicle owner and/or the repairer may be liable for prosecution.

The emission control system fitted to the vehicle is designed to keep the emissions within the legal limits provided that the engine is correctly maintained and is in good mechanical condition.

Crankcase Emission Control System

Gases from the crankcase are drawn into the throttle housing to be burnt in the combustion chambers with the fuel mixture. The system provides effective emission control while the engine is running under all circumstances.

There are two breather pipes connected to the throttle housing, one either side of the throttle disc. When the engine is running with the throttle disc open, both pipes are subject to manifold depression and draw crankcase fumes into the manifold. When the throttle disc is closed, only the pipe on the inlet manifold side of the disc is subject to manifold depression. This pipe incorporates a restrictor to prevent engine oil being drawn into the engine by the substantially greater manifold depression.

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 silencer. The catalytic converter reduces the emission of Carbon Monoxide, Oxides of Nitrogen and Hydrocarbons released into the atmosphere. The active constituents of the converter are the precious metals Platinum and Rhodium.

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 upstream of the catalytic converter, in the exhaust manifold (up to 2001 MY) or front pipe (from 2001 MY). 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.

From 2001 MY, a downstream heated oxygen sensor is installed in the outlet of the catalytic converter. By comparing the inputs from the upstream and downstream heated oxygen sensors, the ECM can monitor the efficiency of the catalytic converter.

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.