Coolant Temperature Sensor; Extra Air Valve - Triumph TR7 Owner's Manual

EMISSION AND EVAPORATIVE LOSS CONTROL SYSTEMS
Coolant Temperature Sensor
This sensor is localed al the top of the engme (TRl) or
between the cylinder heads (TRS and Rover 3500) and
provides coolant temperature mformatlon to the ECU. This
information causes the ECU. to lengthen the time that the
main injectors are 'open' redUCing this lime as the engine
warms up and cutting it off when normal engine operating
temperture is reached. In practice the sensor functions by
modifying an output voltage from the E.CU through an
'earth' return Circuit.
Extra Air Valve
This valve is mounted above a water passage near the Inlet
manifold and registers the same temperature as the engme
coolant. Its purpose is to provide the additional air required
to maintam a satisfactory engine Idle speed until the engine
reaches normal operating temperature. This air IS taken from
a point before the throttle butterfly (but after the Air Flow
Meter. so that the air is registered by the E.CU,) and returned
10
the plenum chamber after the throttle butterfly.
To allow air to pass through the Extra Air Valve. and thus by-
pass the throttle butterfly. an opening in a rotatable metal
disc is aligned with the inlet and outlet tubes on the valve
The position of this disc is controlled by a bi-metal striP
which deflects according
10
the temperature It experiences
As the bi-metal strip heats up it rotates the metal diSC until its
opening no longer lines up with the air valve tubes and the
extra air source is reduced and finally terminated as normal
engine operating temperature is reached. The bi-metal strip
is heated from two sources. the coolant temperature and a
heater coil around the strip. The heater colliS energised from
the fuel injection system combined relay while the engine IS
running,
2164
Fig. 17 Coolant tempertute sensor
Fig. 18 Extra air valve
15