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THE DIESEL The diesel engines ignite for spontaneous combustion at

temperatures above 650°C. The rising of the temperature
GLOW PLUGS is given by the compression of the air into the cylinder that,
depending on the engines, passes from the pressure of 1 bar to
20/30 bars with the consequent combustion of the gasoil.

During the ignition phase, with cold engine, cold walls of the
pistons and cold chamber of combustion, part of the heat
produced by the compression is absorbed and lost preventing
the possibility of spontaneous combustion. The glow plugs work
as additional source of heat to compensate for those losses. After
the ignition phase, the heat emitted by the combustion is able to
keep the lowest temperature for spontaneous combustion, but
the conditions still remain critical: in fact the gasoil does not burn
properly and causes black smoke and smell of naphtha; that
goes on until the engine reaches the temperature for optimal
running. That situation was usual with the single coil glow plugs
of frst generation.

Modern engines are equipped with glow plugs of new generation,
called of pre- and post-heating; those glow plugs are able to run
longer thanks to a special flament that keeps the temperature
regulated longer.
Thanks to that new type of glow plugs, the diesel engines are less
noisy, without odour, moderate in the consumptions and with low
emissions of harmful oxides. Those glow plugs are structured
with double-coil technology:

the frst one is a flament of regulation, that allows a self-
regulation of the intensity of current that crosses it in function
of the reached temperature;

the second one is an incandescent flament that allows to
reach the temperature of 1000°C about for some seconds and
then to start the spontaneous combustion.

That combination increases the longevity of the glow plug and
guarantees its total reliability under all the climatic conditions.

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