Engine Mechanical - Audi 4.2-liter V8 FSI Service Training

Cylinder Block
The cylinder crankcase has a closed-deck design, which 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
aluminum-silicon alloy, is hypereutectic* and has a
silicon content of 17 % (AlSi17Cu4Mg).
The cylinder crankcase underwent special heat
treatment 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 minimize 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-on cylinder manifold.
Cylinder Block
Top Section
Press-fit
Main Bearings
Cylinder Block
Bottom Section
The cylinder crankcase lower section (bedplate bearing
cross-member) is made of aluminum with press-fitted
iron main bearing covers made of grade 50 nodular cast
iron. It is centered using centering pins, sealed with
liquid sealant and bolted to the cylinder crankcase.

Engine Mechanical

*Aluminum 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 precipitated on solidification of
the molten metal.
A multistage honing process is applied. The silicon grains
in the cylinder bores in the form of microscopically 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
The main bearing is symmetric with the center of the
main bearing, attached by four bolts. The bedplate type
design provides high stability. The bedplate has the same
stabilizing effect as a ladder frame.
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