Range Rover P38 Emission Control - Land Rover V8
17
EMISSION CONTROL
NEW RANGE ROVER
6
DESCRIPTION AND OPERATION
Crankcase ventilation 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, filter or excessive air leak into the
inlet system through a damaged pipe or leaking
gasket can affect the air:fuel mixture, performance
and economy 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 burning them in
the combustion chambers. 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.
When the engine is running in cruise conditions, or at
idle, manifold pressure is low and the majority of
gasses are drawn into the inlet manifold through an
oil/vapour separator (1), located in the RH rocker
cover. At the same time, filtered air is drawn from the
throttle body (3) into the engine via the LH rocker
cover (2). The oil/vapour separator serves to prevent
oil mist being drawn into the engine.
During periods of driving at Wide Open Throttle
(WOT), pressure at either side of the throttle disc
equalizes (manifold depression collapses). The larger
ventilation opening (3), positioned in the fast moving
stream of intake air, now offers more ’pull’ than the
small opening (1) in the RH rocker cover, and the flow
of ventilation reverses. Gases are drawn from the LH
rocker cover into the throttle body (3).
