CITROEN DS series Technical Manual page 14

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The Citroën Guide
Towards a cleaner world
Exhaust Gas Recycling (EGR) systems were used—depend-
ing on the market—as add-on units. An electronic unit mea-
suring the coolant temperature and the position of the gas
pedal control on the pump (with a potentiometer fitted to
the top of the control lever) controls a valve which lets part
of the exhaust gas get back into the inlet.
Post-glowing is also used as a pollution reducing mecha-
nism. A definite post-glow phase, lasting for up to minutes
is usually controlled by a combination of a timer and the en-
gine coolant temperature: either the timeout of 4 minutes
runs out or the engine reaches 50 °C. An additional mecha-
nism prevents post-glowing if the engine was not actually
started.
Fuel Injection: Diesel engines 14