Emission control - K Series 1.8 (Description): Description and operation

Description

General

The vehicle is fitted with the following control systems to reduce emissions released into the atmosphere: l Crankcase emission control. l Evaporative emissions (EVAP) control. l Exhaust emission control.

CAUTION: In many countries it is against the law for a vehicle owner or an unauthorised dealer to modify or tamper with emission control equipment. In some cases, the vehicle owner and/or the dealer may even be liable for prosecution.

The emission control systems fitted to the vehicle are designed to keep the emissions within the legal limits, at the time of manufacture, provided that the engine is correctly maintained and is in good mechanical condition.

Crankcase Emission Control System

While the engine is running, blow-by gases from the crankcase are mixed with inlet air and burned in the combustion chambers.

The crankcase is vented via the oil drain passages in the cylinder block and cylinder head and two ports in the camshaft cover. The larger port in the camshaft cover is connected to the throttle body, on the upstream side of the throttle disc, by a plastic pipe and rubber elbow connections. The smaller port in the camshaft cover is connected to the inlet manifold by a rubber hose. The smaller port incorporates a restrictor and a gauze oil separator to prevent oil being drawn out of the camshaft cover.

When the engine is running with the throttle disc closed, the depression downstream of the throttle disc draws crankcase gases into the inlet manifold through the smaller port in the camshaft cover. Clean air, from the upstream side of the throttle disc, is drawn into the crankcase through the larger port in the camshaft cover to limit the depression produced in the crankcase.

When the engine is running with the throttle disc wide open, the upstream and downstream sides of the throttle disc, and thus the two ports in the camshaft cover, are subjected to similar, relatively weak, depression levels. Crankcase gases are then drawn out of both ports in the camshaft cover, with the majority being drawn out of the unrestricted larger port and into the throttle body.

At interim throttle disc positions the flow of the crankcase gases varies, between those produced at the closed and wide open throttle disc positions, depending on the depression levels produced upstream and downstream of the throttle disc.

Exhaust Emission Control

The engine management systems provide accurately metered quantities of fuel to the combustion chambers to ensure the most efficient use of fuel and to minimise the exhaust emissions. In European Union markets, to reduce the carbon monoxide and hydrocarbons content of the exhaust gases, two catalytic converters are installed in the exhaust system. A 'starter' catalytic converter is integrated into the exhaust manifold and a main catalytic converter is integrated into the exhaust system front pipe.

In the catalytic converters the exhaust gases are passed through honeycombed ceramic elements coated with a special surface treatment called 'washcoat'. The washcoat increases the surface area of the ceramic elements by a factor of approximately 7000. On top of the washcoat is a coating containing the elements which are the active constituents for converting harmful emissions into inert by-products. The active constituents consist of palladium and platinum, which add oxygen to the carbon monoxide and the hydrocarbons in the exhaust gases, to convert them into carbon dioxide and water respectively.

The correct operation of the catalytic converters is dependent upon close control of the oxygen content of the exhaust gas. The quantity of oxygen in the exhaust gas is monitored by the Engine Control Module (ECM) using an input from a Heated Oxygen Sensor (HO2S) upstream of the starter catalytic converter. The ECM also monitors the condition of the catalytic converters using an input from a HO2S downstream of the main catalytic converter.