Emission Control Systems (Emission control - Td5)

Emission Control Systems

Engine design has evolved in order to minimise the emission of harmful by-products. Emission control systems fitted to Land Rover vehicles 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 optimum condition.

In addition to emissions improvements through engine design and the application of electronic engine management systems, special emission control systems are used to limit the pollutant levels developed under certain conditions. Two main types of additional emission control system are utilised with the Td5 engine to reduce the levels of harmful emissions released into the atmosphere. These are as follows: 1 Crankcase emission control – also known as blow-by gas emissions from the engine crankcase. 2 Exhaust gas recirculation – to reduce NO₂ emissions.

Crankcase emission control

All internal combustion engines generate oil vapour and smoke in the crankcase as a result of high crankcase temperatures and piston ring and valve stem blow-by, a closed crankcase ventilation system is used to vent crankcase gases back to the air induction system and so reduce the emission of hydrocarbons.

Gases from the crankcase are drawn into the inlet manifold to be burnt in the combustion chambers with the fresh air/ fuel mixture. The system provides effective emission control under all engine operating conditions.

Crankcase gases are drawn through the breather port in the top of the camshaft cover and routed through the breather hose and breather valve on the flexible air intake duct to be drawn into the turbocharger intake for delivery to the air inlet manifold via an intercooler.

An oil separator plate is included in the camshaft cover which removes the heavy particles of oil before the crankcase gas leaves via the camshaft cover port. The rocker cover features circular chambers which promote swirl in the oil mist emanating from the cylinder head and camshaft carrier. As the mist passes through the series of chambers between the rocker cover and oil separator plate, oil particles are thrown against the separator walls where they condense and fall back into the cylinder head via two air inlet holes located at each end of the rocker cover.

The breather valve is a depression limiting valve which progressively closes as engine speed increases, thereby limiting the depression in the crankcase. The valve is of moulded plastic construction and has a port on the underside which plugs into a port in the flexible air intake duct. A port on the side of the breather valve connects to the camshaft cover port by means of a breather hose which is constructed from a heavy-duty braided rubber hose which is held in place by hose clips. A corrugated plastic sleeve is used to give further protection to the breather hose. The breather valve is orientation sensitive, and “TOP” is marked on the upper surface to ensure it is mounted correctly.

It is important that the system is airtight so hose connections to ports should be checked and the condition of the breather hose should be periodically inspected to ensure it is in good condition.