Ima Injector Classification; Variable Geometry Intake Actuator - Alfa Romeo 159 Training Material

ENGINE
ATOMISER ACTUATOR: The actuator/atomiser consists of the nozzle and the pressure rod-pin assembly. The
nozzle is supplied with pressurised fuel when the pressure rod-pin assembly is raised. The latter is lifted by the
imbalance of counterpoised forces on the assembly. Three forces act on the pressure rod-pin system:
Elastic force F , in the direction of closure due to the spring on the pin. This force ensures tightness of the nozzle
e
when the line pressure drops to zero and avoids dripping of fuel into the cylinder.
Force F also in the direction of closure due to the pressure of the fuel in the check port. This pressure acts on the
c
upper area of the pressure rod.
Force F , in the direction of opening is due to the pressure of the fuel in the feeding port and acts on the circular
a
crown area delimited on the outside by the sliding diameter of the pin in the nozzle and the seal diameter of the
tapered seat.
The balance of the pressure rod-pin assembly depends on the balance of these three forces. The pressure in the
feeding port and in the check port are identical and equal to the line pressure provided by the rail when the injector is
not energised. In these conditions:

IMA injector classification

Injectors are inspected and the characteristics in various conditions of pressure/flow rate are tested. Any injectors
which are not up to standards are eliminated. The injectors that pass the tests are classified with a 9-character
alphanumeric code, called IMA code (see arrow in figure above). The code is laser engraved on the top of the injector
magnet.
The IMA code of the injectors must be stored in the ECU (using Examiner) after replacing one or more injectors.

Variable geometry intake actuator

LOCATION: In the engine compartment, connected to the intake manifold.
FUNCTION: To control throttle operation and optimise swirl in the combustion chamber.
CONSTRUCTION: The variable swirl system essentially consists of:
Traccia Didattica Alfa 159-en-ridotta
ALFA 159 TRAINING MATERIAL
F + F > F
c e a
ALIM.
VARIABLE SWIRL
ACTUATOR
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