Emission Control Systems (Emission control - V8)

Emission Control Systems

Engine design has evolved in order to minimise the emission of harmful by-products. Emission control systems are fitted to Land Rover vehicles which are designed to maintain the emission levels within the legal limits pertaining for the specified market.

Despite the utilisation of specialised emission control equipment, it is still necessary to ensure that the engine is correctly maintained and is in good mechanical order so that it operates at its optimal condition. In particular, ignition timing has an effect on the production of HC and NO_x emissions, with the harmful emissions rising as the ignition timing is advanced.

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 engine management ECM is fundamental for controlling the emission control systems. In addition to controlling normal operation, the system complies with On Board Diagnostic (OBD) system strategies. The system monitors and reports on faults detected with ignition, fuelling and exhaust systems which cause an excessive increase in tailpipe emissions. This includes component failures, engine misfire, catalyst damage, catalyst efficiency, fuel evaporative loss and exhaust leaks.

When an emission relevant fault is determined, the fault condition is stored in the ECM memory. For NAS vehicles, the MIL warning light on the instrument pack will be illuminated when the fault is confirmed. Confirmation of a fault condition occurs if the fault is still found to be present during the driving cycle subsequent to the one when the fault was first detected. ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine management.

The following types of supplementary control system are used to reduce harmful emissions released into the atmosphere from the vehicle: 1 Crankcase emission control – also known as blow-by gas emissions from the engine crankcase. 2 Exhaust emission control – to limit the undesirable by-products of combustion. 3 Fuel vapour evaporative loss control – to restrict the emission of fuel through evaporation from the fuel system. 4 Fuel leak detection system (NAS only) – there are two types of system which may be used to check the evaporative emission system for the presence of leaks from the fuel tank to purge valve. a Vacuum leak detection test – checks for leaks down to 1 mm (0.04 in.) in diameter. b Positive pressure leak detection test – utilises a leak detection pump to check for leaks down to 0.5 mm (0.02 in.) in diameter. 5 Secondary air injection system (NAS only) – to reduce emissions experienced during cold starting.

Crankcase emission control system

The concentration of hydrocarbons in the crankcase of an engine is much greater than that in the vehicle's exhaust system. In order to prevent the emission of these hydrocarbons into the atmosphere, crankcase emission control systems are employed and are a standard legal requirement.

The crankcase ventilation system is an integral part of the air supply to the engine combustion chambers and it is often overlooked when diagnosing problems associated with engine performance. A blocked ventilation pipe or filter or excessive air leak into the inlet system through a damaged pipe or a leaking gasket can affect the air:fuel mixture, performance and efficiency of the engine. Periodically check the ventilation hoses are not cracked and that they are securely fitted to form airtight connections at their relevant ports.

The purpose of the crankcase ventilation system is to ensure that any noxious gas generated in the engine crankcase is rendered harmless by complete burning of the fuel in the combustion chamber. Burning the crankcase vapours in a controlled manner decreases the HC pollutants that could be emitted and helps to prevent the development of sludge in the engine oil as well as increasing fuel economy.