Diesel Engines Advance; Diesel Ignition Engines - tecnotest 232-E Mode D'emploi

__________________________________________________________________________ TIMING LIGHT
1.3 -

Diesel engines advance

In diesel engines the diesel fuel injection into the bursting chamber, where the air
heated by the piston compression is present, starts the combustion - expansion.
Despite the high temperature of the compressed air in the cylinder the ignition of the
injected fuel is not simultaneous, hence the injection has to be advanced of a
certain degree with regard to the Top Dead Centre.
An incorrect advance regulation can cause fumes at the exhaust, a lack of efficiency,
engine overheating and functioning roughness.
On the basis of the engine features (rapid diesel) it might be necessary to furtherly
increase the advance angle according to the revolution number.
The higher the revolution number, the shorter the available time for the injection and
the fuel complete combustion.
Hence, the injection advance angle has to be increased since the engine shaft rotates
more rapidly and reaches earlier the TDC; in these cases a device called Variator is
used to perform this task.
1.4 -

Diesel ignition engines

Two types of injection exist:
In the engine head there is an auxiliary combustion chamber, the so called swirl
chamber or precombustion chamber, connected to the cylinder through an oblique
passage.
The air compressed by the piston occupies the space of the swirl chamber, where the
fuel is injected by the injector, located on an angle of the air vortex.
The gas mixture produced in the chamber is forced into the cylinder where it mixes with
the remaining combustion air.
In the direct injection the combustion chamber is located directly on the piston crown.
The injector is positioned centrally with regard to the combustion chamber where the
injected fuel mixes with the compressed air and burns.
In the direct injection engines the combustion is performed more rapidly than in
engines with precombustion chamber.
SERVICE MANUAL
INDIRECT INJECTION
DIRECT INJECTION
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