Audi 4.2-litre V8 FSI, Service Training

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*Aluminium alloys are classed as hypoeutectic or
hypereutectic, depending on their silicon content.
"Alusil" has a hypereutectic silicon content of 16 to
18 % so that primary silicon is precicipated on
solidification of the molten metal.
A multistage honing process is applied. The silicon
grains in the cylinderbores in the form of micro-
scopically small, very hard particles are stripped to
give the necessary wear resistance of the cylinder
surfaces for the piston and piston rings.
– Cylinder spacing: 90 mm
– Cylinder bank offset: 18.5 mm
– Overall engine length: 464 mm
– Cylinder block height: 228 mm
Engine mechanicals
Cranktrain
Cylinder block
The cylinder crankcase has a closed-deck design.
The closed-deck design is stronger than the open-
deck design.
In an open-deck cylinder block, the water jacket for
cooling the cylinders is open at the top.
The cylinder crankcase is made of a low-pressure
gravity diecast aluminium-silicon alloy, is
hypereutectic* and has a silicon content of 17 %
(AlSi17Cu4Mg).
The cylinder crankcase underwent special heat
treatment in order to increase its strength.
The cylinder liners are mechanically stripped.
The cylinder crankcase of the high-revving engine
was machined to higher specifications due to the
higher stresses in this component. To minimise
warping of the cylinder manifolds, the crankcase is
honed under stress. For this purpose, a honing
template is attached to the crankcase before the
honing process in order to simulate the warping of
the bolted cylinder manifold.
The
cylinder crankcase lower section
(bedplate
bearing cross-member) is made of aluminium with
press-fitted iron main bearing covers made of grade
50 nodular cast iron. It is centred using centring
pins, sealed with liquid sealant and bolted to the
cylinder crankcase.
The main bearing is symmetrically to the centre of
the main bearing attached by four bolts.
The bedplate type design provides high stability.
The bedplate has the same stabilising effect as a
ladder frame.
Cylinder crankcase bottom section
Press-fitted main bearing
Cylinder crankcase