Emission control - K Series KV6 (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 Exhaust emission control. l Evaporative emissions (EVAP) 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 and the fuel system components are correctly maintained and in good mechanical condition.

Crankcase Emission Control System

The crankcase is vented via the oil drain passages in the cylinder blocks and cylinder heads and two ports in each camshaft cover. Plastic pipes connect the larger ports in the camshaft covers to either the throttle body (all except NAS) or the intake duct (NAS), on the upstream side of the throttle disc. The smaller ports in the camshaft covers are connected to the inlet manifold, downstream of the throttle body, also by plastic pipes. Each of the smaller ports incorporate a restrictor and a gauze oil separator to prevent oil being drawn out of the camshaft covers with the blowby gases. Quick release locking collars and 'O' rings are used for all of the pipe connections with the camshaft covers, throttle body and air intake duct.

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 ports in the camshaft covers. Clean air, from the upstream side of the throttle disc, is drawn into the crankcase through the larger ports in the camshaft covers 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 each camshaft cover, are subjected to similar, relatively weak, depression levels. Crankcase gases are then drawn out of both ports in each camshaft cover, with the majority being drawn out of the unrestricted larger ports 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 some markets, to reduce the carbon monoxide and hydrocarbons content of the exhaust gases, catalytic converters are installed in the exhaust system. Where catalytic converters are fitted: l In all except NAS markets, a 'starter' catalytic converter is integrated into each exhaust manifold and a main catalytic converter is integrated into the exhaust system front pipe. l In NAS markets, a catalytic converter is integrated into each downpipe close to the exhaust manifolds.

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 platinum and rhodium. Platinum adds oxygen to the carbon monoxide and the hydrocarbons in the exhaust gases, to convert them into carbon dioxide and water respectively. The rhodium removes oxygen from the Nitrous Oxides (NOx) to convert them into nitrogen.