Camshaft; Drive Chains - Alfa Romeo 159 Training Material

ENGINE

Camshaft

1. Valve
2. Valve stem cap
3. Spring
4. Hydraulic tappets
5. Roller rocker arm
6. Continuous variable timing
7. Camshaft
8. Timing sensor phonic wheel
MATERIAL: The camshafts are made of cast iron. Cams are tempered and hardened. The surface treatment
increases surface hardness of the cams and increases resistance to wear.
FEATURES: The camshaft is driven by a chain whose main advantage, with respect to a belt system, is that it does
not need to be replaced for the entire life of the engine. There are two suction valves and two exhaust valves for each
cylinder. The spark plugs are positioned vertically between the two valves. The hydraulic tappets used in these
engines automatically cancel valve backlash while the engine is running: this reduces the need for interventions on
the engine and engine noise.
The high area power (the specific power released on the piston) of the engine (80 HP/dm
the adoption of sodium cooled exhaust valves to reach high volumetric yield. The maximum suction valve lift is 10.3
mm for both engine versions.
The roof-shaped combustion chamber has four valves per cylinder with valve valves with respect to a 86 mm bore
(35.3 mm suction and 30.3 mm exhaust) for easy air flow to favour engine performance.
Attention in designed focused greatly on the piston height to contain the total height of the engine despite the 94.6
mm stroke to provide a compression height of only 28 mm; this result is excellent considering the high area power
reached.

Drive chains

FEATURES: One chain drives the camshaft and another drives the balancing countershafts and the coolant pump.
Two maintenance-free hydraulic tensioners ensure that the chains are correctly pulled. The timing chains cross two
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for the 2.2 litre) called for
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