Alfa Romeo 159 Training Material page 66

ENGINE
FUNCTION: The electro-hydraulic variable timing replaces the standard camshaft control system. It controls and
varies the timing diagram according to the engine conditions to increase the power peak at high speed and decrease
HC, NOx emissions and fuel consumption at the same time.
FEATURES: These engine fit two variable timing systems, one on each camshaft. They are capable of varying the
cam angle during engine operation according to conditions of use. The variable timing on suction side provides
continuous variation of camshaft slant by even 30°. The variable timing on exhaust side allows a rotation of 25°. The
engine ECU determines the position of the cam through the sensors arranged on the camshaft and the crankshaft
and sets the position of the control valve fitted on the head which controls the oil flow into the variable timing system.
ADVANTAGES:
Optimal dimensions (minimum length, minimum diameter).
Capacity of reaching high torque values.
Low weight due to small dimensions and use of alternative materials.
Simple assembly (single central bolt and fastening pin).
System operation
1. Control valve, exhaust side
2. Control valve, suction side
3. Variable timing, exhaust side
4. Variable timing, suction side
5. Reversible oil duct
6. Oil return duct
7. Oil delivery duct
OPERATION: The hydraulic variable timing system is shown in the figure. Duct (7) supplies the 4/3 distributor
hydraulic solenoid valves (four ports, three positions) each of which is connected to its own rotating actuator (variable
timing) via two ducts. The variable timing compartments between the rotor (fixed to camshaft) and the stator (fixed to
pulley) can be filled with oil or emptied. The rotor is turned by the filling and emptying of the conduits. The rotor can
turn with respect to the stator in either direction.
Traccia Didattica Alfa 159-en-ridotta
ALFA 159 TRAINING MATERIAL
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