Alfa Romeo 159 Training Material page 52

ENGINE
FUNCTION: The flywheel makes engine operation smooth by accumulating kinetic energy during the active stroke of
the engine and letting it out during the three passive strokes; this ensures smoother engine running because the
engine power output to the driveline is stabilised by the flywheel.
FEATURES: The engines dealt with here fit a dual-mass flywheel, one fastened to the crankshaft and the other
connected to the primary gearbox shaft. An elastic double stiffness damping system is arranged between these two
rotating masses with springs of different elastic stiffness and a planetary gear set with sun and planetary gears. Other
advantage of this type of flywheel is the low vibrations of the crankshaft-flywheel system at slow engine speeds
(engine cranking).
ADVANTAGES: The adoption of this type of flywheel better filters the vibrations induced by the engine to the
transmission and to the rest of the driveline, improving driving comfort and reducing transmission of abnormal loads
to the gearbox.
1. Shoe
2. Planetary gear
3. Sun gear
4. Primary flywheel (fastened to crankshaft)
5. Tangentially arranged helical springs
DMF (DUAL-MASS FLYWHEEL) OPERATION The two masses are connected together by springs to provide a high
reduction of vibrations induced by the engine to the transmission especially at slower engine speed when the
vibrations are higher. This increases driving comfort, especially at low engine speed.
The features of the flywheel include:
Variable damping
Serial spring arrangement in guide shoe compartment
Mechanical protection to prevent spring packing
Combination of two damping principles:
Shoe friction on primary flywheel
Damping proportional to speed on planetary gears
No additional damping element is required by the system
Lubricated for life with grease
Neutral performance during cranking and stopping of the engine.
With respect to a traditional driveline, this flywheel reduces oscillation of engine speed transmission taking the
resonance amplitude (causing possible vibrations and roughness in transmission) at sufficiently low engine speed to
prevent interference with the speed range usually employed for driving.
Traccia Didattica Alfa 159-en-ridotta
ALFA 159 TRAINING MATERIAL
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